Papers Repository of the International Centre for Numerical Methods in Engineering (CIMNE)

The Papers Repository of the International Centre for Numerical Methods in Engineering (CIMNE) is an online archive aimed at collecting, preserving, and disseminating digital copies of scientific papers published by researchers of the International Center for Numerical Methods in Engineering (CIMNE).

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CBS versus GLS stabilization of the incompressible Navier–Stokes equations and the role of the time step as stabilization parameter
R. Codina, O. Zienkiewicz

Commun. Numer. Meth. Engng (2001). Vol 18 (2), pp. 99-112

Abstract
In this work we compare two apparently different stabilization procedures for the finite element approximation of the incompressible Navier–Stokes equations. The first is the characteristic‐based split (CBS). It combines the characteristic Galerkin method to deal with convection dominated flows with a classical splitting technique, which in some cases allows us to use equal velocity–pressure interpolations. The second approach is the Galerkin‐least‐squares (GLS) method, in which a least‐squares form of the element residual is added to the basic Galerkin equations. It is shown that both formulations display similar stabilization mechanisms, provided the stabilization parameter of the GLS method is identified with the time step of the CBS approach. This identification can be understood from a formal Fourier analysis of the linearized problem.
Abstract
In this work we compare two apparently different stabilization procedures for the finite element approximation of the incompressible Navier–Stokes equations. The first [...]
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Implementation of a stabilized finite element formulation for the incompressible Navier-Stokes equations based on a pressure gradient projection
R. Codina, J. Blasco, G. Buscaglia, A. Huerta

Int. J. Numer. Meth. Fluids (2001). Vol. 37 (4), pp. 419-444

Abstract
We discuss in this paper some implementation aspects of a finite element formulation for the incompressible Navier-Stokes which allows the use of equal order velocity-pressure interpolations. The method consists in introducing the project of the pressure gradient and adding the difference between the pressure Laplacian and divergence of this new field to the incompressibility equations, both multiplied by suitable algorithmic parameters. The main purpose of this paper is to discuss how to deal with the new variable in the implementation of the algorithm. Obviously, it could be treated as one extra unknown, either explicitly or as a condensed variable. However, we take for granted that the only way or another. Here we discuss some iterative schemes to perform this uncoupling of the pressure gradient projection (PGP) from the calculation of the velocity and the pressure, both for stationary and the transient of the linearization loop and the iterative segregation of the PGP, whereas in the second the main dilemma concerns the explicit or implicit treatment of the PGP.
Abstract
We discuss in this paper some implementation aspects of a finite element formulation for the incompressible Navier-Stokes which allows the use of equal order velocity-pressure [...]
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Numerical modeling of magma withdrawal during explosive caldera-forming eruptions
A. Folch, J. Martí i Castell, R. Codina

Journal of Geophysical Research (2001). Vol. 106 (B8), pp. 16 163-16 175

Abstract
We propose a simple physical model to characterize the dynamics of magma withdrawal during the course of caldera-forming eruptions. Simplification involves considering such eruptions as a piston-like system in which the host rock is assumed to subside as a coherent rigid solid. Magma behaves as a Newtonian incompressible fluid below the exsolution level and as a compressible gas-liquid mixture above this level. We consider caldera-forming eruptions within the frame of fluid-structure interaction problems, in which the flow-governing equations are written using an arbitrary Lagrangian-Eulerian (ALE) formulation. We propose a numerical procedure to solve the ALE governing equations in the context of a finite element method. The numerical methodology is based on a staggered algorithm in which the flow and the structural equations are alternatively integrated in time by using separate solvers. The procedure also involves the use of the quasi-Laplacian method to compute the ALE mesh of the fluid and a new conservative remeshing strategy. Despite the fact that we focus the application of the procedure toward modeling caldera-forming eruptions, the numerical procedure is of general applicability. The numerical results have important geological implications in terms of magma chamber dynamics during explosive caldera-forming eruptions. Simulations predict a nearly constant velocity of caldera subsidence that strongly depends on magma viscosity. They also reproduce the characteristic eruption rates of the different phases of an explosive calderaforming eruption. Numerical results indicate that the formation of vortices beneath the ring fault, which may allow mingling and mixing of parcels of magma initially located at different depths in the chamber, is likely to occur for low-viscosity magmas. Numerical results confirm that exsolution of volatiles is an efficient mechanism to sustain explosive caldera-forming eruptions and to explain the formation of large volumes of ignimbrites.
Abstract
We propose a simple physical model to characterize the dynamics of magma withdrawal during the course of caldera-forming eruptions. Simplification involves considering such [...]
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Space and time error estimates for a first order, pressure stabilized finite element method for the incompressible Navier–Stokes equations
J. Blasco, R. Codina

Applied Numerical Mathematics (2001). Vol. 38 (4), pp. 475-497

Abstract
In this paper we analyze a pressure stabilized, finite element method for the unsteady, incompressible Navier–Stokes equations in primitive variables; for the time discretization we focus on a fully implicit, monolithic scheme. We provide some error estimates for the fully discrete solution which show that the velocity is first order accurate in the time step and attains optimal order accuracy in the mesh size for the given spatial interpolation, both in the spaces L2(Ω) and H10(Ω); the pressure solution is shown to be order 12 accurate in the time step and also optimal in the mesh size. These estimates are proved assuming only a weak compatibility condition on the approximating spaces of velocity and pressure, which is satisfied by equal order interpolations.
Abstract
In this paper we analyze a pressure stabilized, finite element method for the unsteady, incompressible Navier–Stokes equations in primitive variables; for the [...]
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Pressure stability in fractional step finite element methods for incompressible flows
R. Codina

Journal of Computational Physics (2001). Vol. 170 (1), pp. 112-140

Abstract
The objective of this paper is to analyze the pressure stability of fractional step finite element methods for incompressible flows. For the classical first order projection method, it is shown that there is a pressure control which depends on the time step size, and therefore there is a lower bound for this time step for stability reasons. The situation is much worse for a second order scheme in which part of the extremely weak. To overcome these shortcomings, a stabilized fractional step finite element method is also considered, and its stability is analyzed. Some simple numerical examples are presented to support the theoretical results.
Abstract
The objective of this paper is to analyze the pressure stability of fractional step finite element methods for incompressible flows. For the classical first order projection [...]
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Transmission conditions with constraints in finite element domain decomposition methods for flow problems
G. Houzeaux, R. Codina

Comput. Methods Appl. Mech. Engrg., (2001). Vol 17 (3), pp. 179-190

Abstract
This work presents a conservative scheme for iteration‐by‐subdomain domain decomposition (DD) strategies applied to the finite element solution of flow problems. The DD algorithm is based on the iterative update of the boundary conditions on the interfaces between the subregions, the so‐called transmission conditions. The transmission conditions involve the essential and natural boundary conditions of the weak form of the problem, and should ensure strong continuity of the velocity and weak continuity of the traction. As a first approach, the transmission conditions are interpolated using the classical Lagrange interpolation functions. Conservation problems might arise when two adjacent subdomains have a sensibly different mesh spacing. In order to conserve any desired quantity of interest, an interface constraining is introduced: continuity of the transmission conditions are constrained under a scalar conservation equation. An example of mass conservation illustrates the algorithm.
Abstract
This work presents a conservative scheme for iteration‐by‐subdomain domain decomposition (DD) strategies applied to the finite element solution of flow problems. The DD [...]
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A stabilized finite element method for generalized stationary incompressible flows
R. Codina

Comput. Methods Appl. Mech. Engrg., (2001). Vol. 190 (20-21), pp. 2681-2706

Abstract
In this paper we describe a finite element formulation for the numerical solution of the stationary Navier-Stokes equations including Coriolis forces and the permeability of the medium. The stabilized method is based on the algebraic version of the sub-grid scale approach. We first describe this technique for general systems of convection-diffusion-reaction equations and then we apply it to linearized flow equations. The important point is the design of the matrix of stabilization parameters that the method has. This design is based on the identification of the stability problems of the Galerkin method and a scaling of variables argument to determine which coefficients must be included in the stabilization matrix. This, together with the convergence analysis of the linearized problem, leads to a simple expression for the stabilization parameters in the general situation considered in the paper. The numerical analysis of the linearized problem also shows that the method has optimal convergence properties.
Abstract
In this paper we describe a finite element formulation for the numerical solution of the stationary Navier-Stokes equations including Coriolis forces and the permeability [...]
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On the constitutive modeling of coupled thermomechanical phase-change problems
C. Agelet de Saracibar, M. Cervera, M. Chiumenti

International Journal of Plasticity (2001). 17 (12), pp. 1565-1622.

Abstract
This paper deals with a thermodynamically consistent numerical formulation for coupled thermoplastic problems including phase-change phenomena and frictional contact. The final goal is to get an accurate, efficient and robust numerical model, able for the numerical simulation of industrial solidification processes. Some of the current issues addressed in the paper are the following. A fractional step method arising from an operator split of the governing differential equations has been used to solve the nonlinear coupled system of equations, leading to a staggered product formula solution algorithm. Nonlinear stability issues are discussed and isentropic and isothermal operator splits are formulated. Within the isentropic split, a strong operator split design constraint is introduced, by requiring that the elastic and plastic entropy, as well as the phase-change induced elastic entropy due to the latent heat, remain fixed in the mechanical problem. The formulation of the model has been consistently derived within a thermodynamic framework. All the material properties have been considered to be temperature dependent. The constitutive behavior has been defined by a thermoviscous/elastoplastic free energy function, including a thermal multiphase change contribution. Plastic response has been modeled by a J2 temperature dependent model, including plastic hardening and thermal softening. The constitutive model proposed accounts for a continuous transition between the initial liquid state, the intermediate mushy state and the final solid state taking place in a solidification process. In particular, a pure viscous deviatoric model has been used at the initial fluid-like state. A thermomecanical contact model, including a frictional hardening and temperature dependent coupled potential, is derived within a fully consistent thermodinamical theory. The numerical model has been implemented into the computational finite element code COMET developed by the authors. Numerical simulations of solidification processes show the good performance of the computational model developed.
Abstract
This paper deals with a thermodynamically consistent numerical formulation for coupled thermoplastic problems including phase-change phenomena and frictional contact. The [...]
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Advances in FE explicit formulation for simulation of metalforming processes
J. Rojek, O. Zienkiewicz, E. Oñate, E. Postek

Journal of Materials Processing Technology (2001). Vol. 119, pp. 41-47

Abstract
This paper presents some advances of finite element explicit formulation for simulation of metal forming processes. Because of their computational efficiency, finite element programs based on the explicit dynamic formulation proved to be a very attractive tool for the simulation of metal forming processes. The use of explicit programs in the sheet forming simulation is quite common, the possibilities of these codes in bulk forming simulation in our opinion are still not exploited sufficiently. In our paper, we will consider aspects of bulk forming simulation. We will present new formulations and algorithms developed for bulk metal forming within the explicit formulation. An extension of a finite element code for the thermomechanical coupled analysis is discussed. A new thermomechanical constitutive model developed by the authors and implemented in the program is presented. A new formulation based on the so-called split algorithm allows us to use linear triangular and tetrahedral elements in the analysis of large plastic deformations characteristic to forming processes. Linear triangles and tetrahedra have many advantages over quadrilateral and hexahedral elements. Linear triangles and tetrahedra based on the standard formulations exhibit volumetric locking and are not suitable for large plastic strain simulation. The new formulation allows to overcome this difficulty. New formulations and algorithms have been implemented in the finite element code Stampack developed at the International Centre for Numerical Methods in Engineering in Barcelona. Numerical examples illustrate some of the possibilities of the finite element code developed and validate new algorithms.
Abstract
This paper presents some advances of finite element explicit formulation for simulation of metal forming processes. Because of their computational efficiency, finite element [...]
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Combination of the critical displacement method with a damage model for structural instability analysis
E. Oñate, H. Tschöpe, P. Wriggers

Engineering Computations (2001). Vol. 18 (3-4), pp. 642-662

Abstract
The paper describes the extension of the critical displacement method (CDM), presented by Oñate and Matias in 1996, to the instability analysis of structures with non-linear material behaviour using a simple damage model. The extended CDM is useful to detect instability points using a prediction of the critical displacement field and a secant load-displacement relationship accounting for material non-linearities. Examples of application of CDM to the instability analysis of structures using bar and solid finite elements are presented.
Abstract
The paper describes the extension of the critical displacement method (CDM), presented by Oñate and Matias in 1996, to the instability analysis of structures with [...]
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A scalar damage model with a shear retention factor for the analysis of reinforced concrete structures: theory and validation
R. Scotta, R. Vitaliani, A. Saetta, E. Oñate, A. Hanganu

Computers and Structures (2001). Vol. 79 (7), pp. 737-755

Abstract
A local isotropic single parameter scalar model that can simulate the mechanical behaviour of quasi-brittle materials, such as concrete, is described. The constitutive law needs the mechanical characteristics and the fracture energy of concrete to be completely defined. The damage parameter is obtained directly from the value of an equivalent effective stress in order to reduce the computing effort. Due to the unique damage parameter, this model is suitable for the study of quasi-static problems involving monotonically increasing loads. The problem of localisation and mesh dependency have been partially overcome by using an enhanced local method in which a characteristic internal length related to the mesh dimension is employed instead of the characteristic fracture length. In this work, the model was enriched further with the introduction of a shear retention factor that accounts for the friction between the two surfaces of a crack. These new features assure a real improvement of the damage model, maintaining nevertheless its simplicity and low computing cost and making it suitable for the practical solution of large scale problems. Several numerical simulations of experimental tests, concerning fracture tests on concrete specimens and beams failing in shear, have been performed for the validation of the model. The main results from the numerical analyses are described and compared with the experimental ones.
Abstract
A local isotropic single parameter scalar model that can simulate the mechanical behaviour of quasi-brittle materials, such as concrete, is described. [...]
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A finite point method for elasticity problems
E. Oñate, F. Perazzo, J. Canet

Computers and Structures (2001). Vol. 79 (22-25), pp. 2151-2163

Abstract
The basis of the finite point method (FPM) for the fully meshless solution of elasticity problems in structural mechanics is described. A stabilization technique based on a finite calculus procedure is used to improve the quality of the numerical solution. The efficiency and accuracy of the stabilized FPM in the meshless analysis of simple linear elastic structural problems is shown in some examples of applications.
Abstract
The basis of the finite point method (FPM) for the fully meshless solution of elasticity problems in structural mechanics is described. A stabilization [...]
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Rotation‐free triangular plate and shell elements
E. Oñate, F. Zárate

Int. J. Numer. Meth. Engng. (2000). Vol. 47 (1-3), pp. 557-603

Abstract
The paper describes how the finite element method and the finite volume method can be successfully combined to derive two new families of thin plate and shell triangles with translational degrees of freedom as the only nodal variables. The simplest elements of the two families based on combining a linear interpolation of displacements with cell centred and cell vertex finite volume schemes are presented in detail. Examples of the good performance of the new rotation‐free plate and shell triangles are given.
Abstract
The paper describes how the finite element method and the finite volume method can be successfully combined to derive two new families of thin plate and shell triangles with [...]
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Shape variable definition with C0 , C1 and C2 continuity functions
G. Chiandussi, G. Bugeda, E. Oñate

Comput. Methods Appl. Mech. Engrg., (2000). Vol. 188, pp. 727-742

Abstract
The present paper proposes a new technique for the definition of the shape design variables in 2D and 3D optimisation problems. It can be applied to the discrete model of the analysed structure or to the original geometry without any previous knowledge of the analytical expression of the CAD defining surfaces. The proposed technique allows the surface continuity to be preserved during the geometry modification process to be defined a priori. This capability allows for the definition of shape variables suitable for every kind of discipline involved in the optimisation process (structural analysis, fluid-dynamic analysis, crash analysis, aerodynamic analysis, etc.).
Abstract
The present paper proposes a new technique for the definition of the shape design variables in 2D and 3D optimisation problems. It can be applied to the discrete model of [...]
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An anisotropic elastoplastic constitutive model for large deformation analysis of fibre reinforced composites
E. Car, S. Oller, E. Oñate

Comput. Methods Appl. Mech. Engrg., (2000). Vol. 185, pp. 245-277

Abstract
In this work a generalized anisotropic elastoplastic constitutive model in large deformation is presented. It is used for the analysis of fiber-reinforced composite materials in the frame of the finite element method. Mixing theory is applied to simulate the behavior of the composite material. The elastic anisotropic behavior is simulated with classical elasticity theory, while that of a non-proportional anisotropic solid is simulated by means of the proposed generalized anisotropic elastoplastic model. The approach assumes the existence of a real anisotropic space and of a fictitious isotropic space where a mapped fictitious problem is solved. Both spaces are related by means of a linear transformation using a fourth order tensor incorporating complete information on the real anisotropic material. Details of the numerical implementations of the model into a non-linear, large deformations finite element solution scheme are provided. Examples of application showing the performance of the model for the analysis of fiber-reinforced composite materials are given.
Abstract
In this work a generalized anisotropic elastoplastic constitutive model in large deformation is presented. It is used for the analysis of fiber-reinforced composite materials [...]
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A stabilized finite element method for incompressible viscous flows using a finite increment calculus formulation
E. Oñate

Comput. Methods Appl. Mech. Engrg., (2000). Vol. 182 (3-4), pp. 355-370

Abstract
A stabilized finite element formulation for incompressible viscous flows is derived. The starting point are the modified Navier-Stokes equations incorporating naturally the necessary stabilization terms via a finite increment calculus (FIC) procedure. Application of the standard finite element Galerkin method to the modified differential equations leads to a stabilized discrete system of equations overcoming the numerical instabilities emanating from the advective terms and those due to the lack of compatibility between approximate velocity and pressure fields. The FIC method also provides a natural explanation for the stabilization terms appearing in all equations for both the Navier-Stokes and the simpler Stokes equations. Transient solution schemes with enhanced stabilization properties are also proposed. Finally a procedure for computing the stabilization parameters is presented.
Abstract
A stabilized finite element formulation for incompressible viscous flows is derived. The starting point are the modified Navier-Stokes equations incorporating naturally the [...]
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Desarrollos y aplicaciones de modelos de fractura en la escuela de ingenieros de caminos de Barcelona
E. Oñate

Anales de Mecánica de Fractura (2000). Vol. 17, pp. 127-154

Abstract
El artículo es una panorámica de los aspectos teóricos y algunas aplicaciones prácticas de los modelos de fractura desarrollados por diversos grupos en la Escuela de Ingenieros de Caminos de Barcelona (EICB) durante los últimos quince años para el análisis no lineal de estructuras. La motivación fundamental para el desarrollo de estos modelos se centra en el análisis de la seguridad de estructuras de hormigón en masa y armado. La mayor parte de los modelos se basan en la teoría de daño continuo y utilizan el método de los elementos finitos para la solución numérica. Los modelos de daño se han extendido y aplicado también con éxito al análisis de diversas estructuras de edificios históricos. Los desarrollos más recientes de estos modelos en la EICB incluyen la predicción de fenómenos de localización en estructuras de hormigón y el análisis del comportamiento no lineal de estructuras con materiales compuestos. De todos estos modelos se presentan en el artículo unas breves pinceladas, las aplicaciones más relevantes y las referencias donde pueden encontrarse los detalles sobre cada caso.
Abstract
El artículo es una panorámica de los aspectos teóricos y algunas aplicaciones prácticas de los modelos de fractura desarrollados por diversos grupos [...]
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Adaptivity based on error estimation for viscoplastic softening materials
P. Diez, M. Arroyo, A. Huerta

Mechanics of Cohesive-Frictional Materials (2000). Vol. 5 (2), pp. 87-112

Abstract
This paper focuses on the numerical simulation of strain softening mechanical problems. Two problems arise: (1) the constitutive model has to be regular and (2) the numerical technique must be able to capture the two scales of the problem (the macroscopic geometrical representation and the microscopic behavior in the localization bands). The Perzyna viscoplastic model is used in order to obtain a regularized softening model allowing to simulate strain localization phenomena. This model is applied to quasistatic examples. The viscous regularization of quasistatic processes is also discussed: in quasistatics, the internal length associated with the obtained band width is no longer only a function of the material parameters but also depends on the boundary value problem (geometry and loads, specially loading velocity). An adaptive computation is applied to softening viscoplastic materials showing strain localization. As the key ingredient of the adaptive strategy, a residual type error estimator is generalized to deal with such highly nonlinear material model. In several numerical examples the adaptive process is able to detect complex collapse modes that are not captured by a first, even if fine, mesh. Consequently, adaptive strategies are found to be essential to detect the collapse mechanism and to assess the optimal location of the elements in the mesh.
Abstract
This paper focuses on the numerical simulation of strain softening mechanical problems. Two problems arise: (1) the constitutive model has to be regular and (2) the numerical [...]
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Error estimation including pollution assessment for nonlinear finite element analysis
A. Huerta, P. Diez

Comput. Methods Appl. Mech. Engrg., (2000). Vol. 181 (1-3), pp. 21-41

Abstract
A residual type error estimator for nonlinear finite element analysis is introduced. This error estimator solves local problems avoiding both the computation of the flux jumps and the associated flux splitting procedure. Pollution errors are taken into account by a feedback strategy, that is, an error estimate based on local computations is used as the input of the pollution analysis. This estimator is used in the frame of an adaptive procedure. Numerical examples show that the estimator is able to drive adaptive procedures leading to likely good solutions. Moreover, one of the examples demonstrates that adaptive procedures are essential for complex highly nonlinear mechanical problems because they may discover secondary collapse mechanisms.
Abstract
A residual type error estimator for nonlinear finite element analysis is introduced. This error estimator solves local problems avoiding both the computation of the flux jumps [...]
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Error estimation for adaptive computations on shell structures
P. Diez, A. Huerta

European Journal of Finite Elements (2000). Vol. 9 (1-3), pp. 49-66

Abstract
The finite element discretization of a shell structure introduces two kinds of errors: the error in the functional approximation and the error in the geometry approximation. The first is associated with the finite dimensional interpolation space and it is present in any finite element computation. The latter is associated with the piecewise polynomial approximation of a curved surface and is much more relevant in shell problems than in any other standard 2D or 3D computation. In the shells framework, formerly the quality control of the finite element solution has been carried out using flux projection a posteriori error estimators. This technique exhibits two main drawbacks: 1) the flux smoothing averages stress components over different elements that may have different physical meaning if the tangent planes are different and 2) the error estimation process uses only the approximate solution and hence, the discretized forces and the computational mesh: the data describing the real geometry and load is therefore not accounted for. In this work, a residual type error estimator introduced for standard 2D finite element analysis is generalized to shell problems. This allows to easily account for the real original geometry of the problem in the error estimation procedure and precludes the necessity of comparing generalized stress components between non coplanar elements. This estimator is based on approximating a reference error associated with a refined reference mesh. In order to build up the residual error equation the computed solution must be represented (projected) on the reference mesh. The use of thin shell finite elements requires a proper formulation in order to preclude shear locking. Following an idea of Donea and Lamain, the interpolation of the rotations is not unique and requires a particular technique to transfer the information from the computational mesh to the reference mesh. This technique is also developed in this work and may be used in any adaptive evolution problem where the solution must be transferred from one mesh to another.
Abstract
The finite element discretization of a shell structure introduces two kinds of errors: the error in the functional approximation and the error in the geometry approximation. [...]
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Stabilization of incompressibility and convection through orthogonal sub-scale in finite element methods
R. Codina

Comput. Methods Appl. Mech. Engrg., (2000). Vol. 190 (13-14), pp. 1579-1599

Abstract
Two apparently different forms of dealing with the numerical instability due to the incompressibility constraint of the stokes problem are analyzed in this paper. The first of them is the stabilization thought the pressure gradient projection, which consists of adding a certain least-squares form of the difference between the pressure gradient and its L² projection onto the discrete velocity space in the variational equations of the problem. The second is a sub-grid scale method, whose stabilization effect is very similar to that of the Galerkin/least-squares method for the Stokes problem. It is shown here that the first method can also be recast in the framework of sub-grid scale method with a particular choice for the space of sub-scales. This leads to a new stabilization procedure, whose applicability to stabilize convection is also studied in this paper.
Abstract
Two apparently different forms of dealing with the numerical instability due to the incompressibility constraint of the stokes problem are analyzed in this paper. The first [...]
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Analysis of a pressure-stabilized finite element approximation of the stationary Navier-Stokes equations
R. Codina, J. Blasco

Numerische Mathematik (2000). Vol. 87 (1), pp. 59-81

Abstract
The purpose of this paper is to analyze a finite element approximation of the stationary Navier-Stokes equations that allows the use of equal velocity-pressure interpolation. The idea is to introduce as unknown of the discrete problem the projection of the pressure gradient (multiplied by suitable algorithmic parameters) onto the space of continuous vector fields. The difference between these two vectors (pressure gradient and projection) is introduced in the continuity equation. The resulting formulation is shown to be stable and optimally convergent, both in a norm associated to the problem and in the L2 norm for both velocities and pressure. This is proved first for the Stokes problem, and then it is extended to the nonlinear case. All the analysis relies on an inf-sup condition that is much weaker than for the standard Galerkin approximation, in spite of the fact that the present method is only a minor modification of this.
Abstract
The purpose of this paper is to analyze a finite element approximation of the stationary Navier-Stokes equations that allows the use of equal velocity-pressure interpolation. [...]
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Fourier analysis of an equal‐order incompressible flow solver stabilized by pressure gradient projection
G. Buscaglia, F. Basombrío, R. Codina

Int. J. Numer. Meth. Fluids (2000). Vol. 34 (1), pp. 65-92

Abstract
Fourier analysis techniques are applied to the stabilized finite element method (FEM) recently proposed by Codina and Blasco for the approximation of the incompressible Navier–Stokes equations, here denoted by pressure gradient projection (SPGP) method. The analysis is motivated by spurious waves that pollute the computed pressure in start‐up flow simulation. An example of this spurious phenomenon is reported. It is shown that Fourier techniques can predict the numerical behaviour of stabilized methods with remarkable accuracy, even though the original Navier–Stokes setting must be significantly simplified to apply them. In the steady state case, good estimates for the stabilization parameters are obtained. In the transient case, spurious long waves are shown to be persistent when the element Reynolds number is large and the Courant number is small. This can be avoided by treating the pressure gradient projection implicitly, though this implies additional computing effort. Standard extrapolation variants are unfortunately unstable. Comparisons with Galerkin–least‐squares (GLS) method and Chorin's projection method are also addressed
Abstract
Fourier analysis techniques are applied to the stabilized finite element method (FEM) recently proposed by Codina and Blasco for the approximation of the incompressible Navier–Stokes [...]
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A nodal-based implementation of a stabilized Finite Element Method for Incompressible Flow Problems
R. Codina

Int. J. Numer. Meth. Fluids (2000). Vol. 33 (5), pp. 737-766

Abstract
The objective of this paper is twofold. First, a stabilized finite element method for the incompressible Navier-Stokes is presented, and several numerical experiments are conducted to check its performance. This method is able to deal with all the instabilities that the standard Galerkin method presents, namely, the pressure instability, the instability arising in convection dominated situations and also the less popular instabilities found when the Navier-Stokes equations have a dominant Coriolis force, or there is a dominant absorption term arising from the small permeability of the medium where the flow takes place. The second objective is to describe a nodal-based implementation of the finite element formulation introduced. This implementation is based on an a priori calculation of the integrals appearing in the formulation and then the construction of the matrix approximations, this matrix and this vector can be constructed directly for each nodal point, without the need to loop over element and thus making the calculations much faster. In order to be able to do this, all the variables have to be defined at the nodes of the finite element mesh, not on the elements. This is also so for the stabilization parameters of the formulation. However, doing this given rise to questions regarding the consistency and the conservation properties of the final scheme that are addressed in this paper.
Abstract
The objective of this paper is twofold. First, a stabilized finite element method for the incompressible Navier-Stokes is presented, and several numerical experiments are [...]
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On stabilized finite element methods for linear systems of convection-diffusion-reaction equations
R. Codina

Comput. Methods Appl. Mech. Engrg., (2000). Vol. 188 (200), pp. 61-82

Abstract
A stabilized finite element method for solving systems of convection-diffusion-reaction equations is studied in this paper. The method is based on the subgrid scale approach and an algebraic approximation to the subscales. After presenting the formulation of the method, it is analyzed how it behaves under changes of variables, showing that it relies on the law of change of the matrix of stabilization parameters associated to the method. An expression for this matrix is proposed for the case of general coupled systems of equations that is an extension of the expression proposed for a 1D model problem. Applications of the stabilization technique to the Stokes problem with convection and to the bending of Reissner-Mindlin plates are discussed next. The design of the matrix of stabilization parameters is based on the identification of the stability deficiencies of the standard Galerkin method applied to these two problems.
Abstract
A stabilized finite element method for solving systems of convection-diffusion-reaction equations is studied in this paper. The method is based on the subgrid scale approach [...]
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Stabilized finite element method for the transient Navier–Stokes equations based on a pressure gradient projection
R. Codina, J. Blasco

Comput. Methods Appl. Mech. Engrg., (2000). Vol. 182 (3-4), pp. 277-300

Abstract
In this paper we present a stabilized finite element formulation for the transient incompressible Navier–Stokes equations. The main idea is to introduce as a new unknown of the problem the projection of the pressure gradient onto the velocity space and to add to the incompresibility equation the difference between the Laplacian of the pressure and the divergence of this new vector field. This leads to a pressure stabilization effect that allows the use of equal interpolation for both velocities and pressures. In the case of the transient equations, we consider the possibility of treating the pressure gradient projection either implicitly or explicity. In the first case, the number of unknowns of the problem is substantially increased with respect to the standard Galerkin formulation. Nevertheless, iterative techniques may be used in order to uncouple the calculation of the pressure gradient projection from the rest of unknowns (velocity and pressure). When this vector field is treated explicitly, the increment of computational cost of the stabilized formulation with respect to the Galerkin method is very low. We provide a stability estimate for the case of the simple backward Euler time integration scheme for both the implicit and the explicit treatment of the pressure gradient projection.
Abstract
In this paper we present a stabilized finite element formulation for the transient incompressible Navier–Stokes equations. The main idea is to introduce as a new unknown [...]
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Simulation of Construction of RCC Dams. II: Stress and Damage
M. Cervera, T. Prato, J. Oliver

Journal of Structural Engineering (2000). 126 (9), pp. 1062-1068

Abstract
The increasing number of roller compacted concrete (RCC) dams being built around the world demands accurate methodologies for the realistic short- and long-term evaluations of the risk of thermally induced cracking in these constructions. In this work a numerical procedure for the simulation of the construction process of RCC dams is presented. It takes into account the more relevant features of the behavior of concrete at early ages, such as hydration, aging, creep, and damage. A 2D model of the Urugua-;aaı RCC Dam, built in Argentina, is used to perform the corresponding analyses. In this second part of the paper, the mechanical aspects of the simulation are presented; long-term effects are included by incorporating a creep model that naturally accounts for the aging effects, and the risk of tensile damage is also considered. The methodology determines the stress field inside the dam at any time during the construction and in the following years. Results for the reference case assess the suitability of the adopted design. This is compared to alternative studies considering different construction schedules to conclude that for these cases changes should be introduced in the dam design.
Abstract
The increasing number of roller compacted concrete (RCC) dams being built around the world demands accurate methodologies for the realistic short- and long-term evaluations [...]
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Simulation of Construction of RCC Dams. I: Temperature and Aging
M. Cervera, J. Oliver, T. Prato

Journal of Structural Engineering (2000). 126 (9), pp. 1053-1060

Abstract
The increasing number of roller compacted concrete (RCC) dams being built around the world demands accurate methodologies for the realistic short- and long-term evaluations of the risk of thermally induced cracking in these constructions. In this work a numerical procedure for the simulation of the construction process of RCC dams is presented. It takes into account the more relevant features of the behavior of concrete at early ages, such as hydration, aging, creep, and damage. A 2D model of the Urugua-í RCC Dam, built in Argentina, is used to perform the corresponding analyses. In this first part only the thermochemical aspects of the simulation of the construction process are presented. The temperature distribution and evolution inside the dam are obtained before and after the completion of the dam. The evolution of the compressive and tensile strengths and elastic moduli and their final distribution inside the dam can also be predicted. Results from 2D and simplified vertical 1D models are compared to assess the validity of the latter, and several parametric studies are carried out. The simulation and discussion of the mechanical aspects of the construction process are relegated to a companion paper that follows.
Abstract
The increasing number of roller compacted concrete (RCC) dams being built around the world demands accurate methodologies for the realistic short- and long-term evaluations [...]
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Smoothed surface gradients for panel methods
J. D'Elía, M. Storti, S. Idelsohn

Advances in Engineering Software (2000). Vol. 31 (5), pp. 339-346

Abstract
A weak form to compute the dipolar and monopolar surface gradients, related to a low-order panel method, is shown. The flow problem is formulated by means of a three-dimensional potential model and the discretization is based on Morino's formulation for the perturbation velocity potential. On the body surface, this representation reduces to a boundary integral equation with the source (or monopolar) and the doublet (or dipolar) densities. The first of the two is found by application of the boundary flow condition, and the second one is the unknown over the body surface. A lower panel method is used for the analytic integrations of both the monopolar and dipolar influence coefficients. The surface velocity field is computed after solving the linear system, with a strong and a weak form of the Stokes theorem, which is oriented to fairly non-structured panel meshes. The proposed method is validated by comparing the numerical results with analytical ones for an isolated sphere and includes a prediction over a car-like configuration.
Abstract
A weak form to compute the dipolar and monopolar surface gradients, related to a low-order panel method, is shown. The flow problem is formulated by means of a three-dimensional [...]
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A closed form for low-order panel methods
J. D'Elía, M. Storti, S. Idelsohn

Advances in Engineering Software (2000). Vol. 31 (5), pp. 347-353

Abstract
A closed form for the computation of the dipolar and monopolar influence coefficients related to a low-order panel method is shown. The flow problem is formulated by means of a three-dimensional potential model; the method of discretization is based on the Morino formulation for the perturbation velocity potential. On the body surface this representation reduces to an integral equation with the source (or monopolar) and the doublet (or dipolar) densities. The former is found by application of the boundary condition, and the latter is the unknown over the surface of the body. The lower panel method is used for the analytical integrations of the monopolar and dipolar influence coefficients, with special attention to avoid a logarithmic singularity in the monopolar matrix when flat fairly structured meshes that are common in ship-wave calculations are used.
Abstract
A closed form for the computation of the dipolar and monopolar influence coefficients related to a low-order panel method is shown. The flow problem is formulated by means [...]
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A finite point method for incompressible flow problems
E. Oñate, C. Sacco, S. Idelsohn

Computing and Visualization in Science (2000). Vol. 3 (1), pp. 67-75

Abstract
A stabilized finite point method (FPM) for the meshless analysis of incompressible fluid flow problems is presented. The stabilization approach is based in the finite increment calculus (FIC) procedure developed by Oñate [14]. An enhanced fractional step procedure allowing the semi-implicit numerical solution of incompressible fluids using the FPM is described. Examples of application of the stabilized FPM to the solution of two incompressible flow problems are presented.
Abstract
A stabilized finite point method (FPM) for the meshless analysis of incompressible fluid flow problems is presented. The stabilization approach is based in the finite increment [...]
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Numerical aerodynamic analysis of large buildings using a finite element model with application to a telescope building
R. Codina, C. Morton, E. Oñate, O. Soto

Int. J. of Num. Meths. for Heat and Fluid Flow (2000). Vol. 10 (5-6), pp. 616-633

Abstract
Presents a numerical strategy for the aerodynamic analysis of large buildings, with an application to the simulation of the air flow within a telescope building. The finite element formulation is presented first, and then the methodology followed to obtain significant data from the calculations is described. The quality of the ventilation of the building is defined by the average residence times, and the feasibility of this ventilation by the actions created on the instruments and the general flow pattern.
Abstract
Presents a numerical strategy for the aerodynamic analysis of large buildings, with an application to the simulation of the air flow within a telescope building. The finite [...]
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A simple method for automatic update of finite element meshes
G. Chiandussi, G. Bugeda, E. Oñate

Commun. Numer. Meth. Engng (2000). Vol. 16 (1), pp. 1-19

Abstract
A simple method to automatically update the finite element mesh of the analysis domain is proposed. The method considers the mesh as a fictitious elastic body subjected to prescribed displacements at selected boundary points. The mechanical properties of each mesh element are appropriately selected in order to minimize the deformation and the distortion of the mesh elements. Different selection strategies have been used and compared in their application to simple examples. The method avoids the use of remeshing in the solution of shape optimization problems and reduces the number of remeshing steps in the solution of coupled fluid–structure interaction problems
Abstract
A simple method to automatically update the finite element mesh of the analysis domain is proposed. The method considers the mesh as a fictitious elastic body subjected to [...]
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Finite element solution of free‐surface ship‐wave problems
S. Idelsohn, E. Oñate, C. Sacco

Int. J. Numer. Meth. Engng. (1999). Vol. 45 (5), pp. 503-528

Abstract
An unstructured finite element solver to evaluate the ship‐wave problem is presented. The scheme uses a non‐structured finite element algorithm for the Euler or Navier–Stokes flow as for the free‐surface boundary problem. The incompressible flow equations are solved via a fractional step method whereas the non‐linear free‐surface equation is solved via a reference surface which allows fixed and moving meshes. A new non‐structured stabilized approximation is used to eliminate spurious numerical oscillations of the free surface.
Abstract
An unstructured finite element solver to evaluate the ship‐wave problem is presented. The scheme uses a non‐structured finite element algorithm for the Euler or Navier–Stokes [...]
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Solving structural optimization problems with genetic algorithms and simulated annealing
S. Botello, J. Marroquín, E. Oñate

Int. J. Numer. Meth. Engng. (1999). Vol. 45 (8), pp. 1069-1084

Abstract
In this paper we study the performance of two stochastic search methods: Genetic Algorithms and Simulated Annealing, applied to the optimization of pin‐jointed steel bar structures. We show that it is possible to embed these two schemes into a single parametric family of algorithms, and that optimal performance (in a parallel machine) is obtained by a hybrid scheme. Examples of applications to the optimization of several real steel bar structures are presented.
Abstract
In this paper we study the performance of two stochastic search methods: Genetic Algorithms and Simulated Annealing, applied to the optimization of pin‐jointed steel bar [...]
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A homogeneous constitutive model for masonry
J. Lopez, S. Oller, E. Oñate, J. Lubliner

Int. J. Numer. Meth. Engng. (1999). Vol. 46 (10), pp. 1651-1671

Abstract
Masonry has been a broadly used material since the beginning of human life. Despite its popularity, the analysis of masonry structures is a complex task due to the heterogeneity and the non‐linear material behaviour. The need for reliable analysis procedures capable of predicting damage evolution and failure in historical structures in order to design efficient repair and maintenance has motivated the work of many structural analysts in this field. Here the finite element method has emerged as one of the most powerful procedures for linear and non‐linear analysis of masonry structures. The main problem pending is the development of accurate and efficient constitutive models capable of predicting the behaviour of masonry in the non‐linear range and this has been the motivation of this work. The constitutive model presented is based on the homogenized anisotropic elastoplasticity previously developed by the authors. The effect of anisotropy is introduced by means of fictitious isotropic stress and strain spaces. The material properties in the fictitious isotropic spaces are mapped into the actual anisotropic space by means of a consistent fourth‐order tensor. The advantage of the model is that the classical theory of plasticity can be used to model the non‐linear behaviour in the isotropic spaces. Details of the model for masonry structures and its implementation in a general non‐linear finite element code are given. Examples of application to the analysis of some masonry structures are presented, showing the efficiency of the model.
Abstract
Masonry has been a broadly used material since the beginning of human life. Despite its popularity, the analysis of masonry structures is a complex task due to the heterogeneity [...]
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A large strain explicit formulation for composites
J. Ruberts, S. Oller, E. Casas, S. Proença, E. Oñate

Int. J. Numer. Meth. Engng. (1999). Vol. 46 (10), pp. 1595-1607

Abstract
A geometrically non‐linear formulation for composites and the resulting explicit dynamic finite element algorithm are presented. The proposed formulation assumes that small elastic and large plastic strains, being the anisotropy considered using tensors which map the model variables at each time step into an equivalent isotropic space, where the integration of the rate constitutive equations is performed. The evolution of the internal variables is calculated in the auxiliary spaces, taking into account the material non‐linear behaviour, and the results mapped back to the real stress space. The updating of the mapping tensors for each new spatial configuration allows the treatment of general anisotropic materials under large strain and can be extended to treat multiphase composite materials using the mixing theory. The behaviour of the composite is dictated by the mechanical response of each substance, and the resultant model allows a fully non‐linear analysis combining different material models, such as damage in one compounding substance, elastoplastic behaviour in the other, while a third substance behaves elastically.
Abstract
A geometrically non‐linear formulation for composites and the resulting explicit dynamic finite element algorithm are presented. The proposed formulation assumes that small [...]
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A generalized streamline finite element approach for the analysis of incompressible flow problems including moving surfaces
M. Cruchaga, E. Oñate

Comput. Methods Appl. Mech. Engrg., (1999). Vol. 173, pp. 241-255

Abstract
In the present work a generalized streamline finite element formulation able to deal with incompressible flow problems is presented. In the finite element framework, this technique allows the use of equal order interpolation for the unknowns of the problem: velocity and pressure. In this context, stable and convergent solutions can be obtained without requiring tuning parameters defined outside this model. The tracking of moving surfaces is also included in the numerical model. This formulation has been checked in 21) and 3D tests.
Abstract
In the present work a generalized streamline finite element formulation able to deal with incompressible flow problems is presented. In the finite element framework, this [...]
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Adaptive finite element strategies based on error assessment
A. Huerta, A. Rodríguez-Ferran, P. Diez, J. Sarrate

Int. J. Numer. Meth. Engng. (1999). Vol. 46 (10), pp. 1803-1818

Abstract
Two main ingredients are needed for adaptive finite element computations. First, the error of a given solution must be assessed, by means of either error estimators or error indicators. After that, a new spatial discretization must be defined via h, p or r-adaptivity. In principle, any of the approaches for error assessment may be combined with any of the procedures for adapting the discretization. However, some combinations are clearly preferable. The advantages and limitations of the various alternatives are discussed. The most adequate strategies are illustrated by means of several applications in solid mechanics.
Abstract
Two main ingredients are needed for adaptive finite element computations. First, the error of a given solution must be assessed, by means of either error estimators or error [...]
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A unified approach to remeshing strategies for finite element h-adaptivity
P. Diez, A. Huerta

Comput. Methods Appl. Mech. Engrg., (1999). Vol. 176 (1-4), pp. 215-229

Abstract
In h-adaptivity, a remeshing strategy is needed to compute the distribution of required element size using the estimated error distribution. Several authors have introduced different remeshing strategies yielding very different results. In this work these methods are included in a unified framework, emphasizing the role of the underlying hypotheses. Moreover, an objective tool to evaluate the accuracy of the resulting finite element solution is presented. Thus, a new remeshing strategy is introduced to optimize the accuracy of the adapted solutions. The different remeshing strategies are compared with well-known numerical examples.
Abstract
In h-adaptivity, a remeshing strategy is needed to compute the distribution of required element size using the estimated error distribution. Several authors have introduced [...]
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Finite element simulation of the filling of thin moulds
R. Codina, O. Soto

Int. J. Numer. Meth. Engng. (1999). Vol. 46 (9), pp. 1559-1573

Abstract
In this work we present a finite element formulation to simulate the filling of thin moulds. The model has as starting point a 3‐D approach using either div‐stable elements, such as the Q2/P1 element (tri‐quadratic velocities and piecewise linear, discontinuous pressures) or stabilized finite element formulations. The tracking of the free surface is based on the Volume‐Of‐Fluid (VOF) method. The velocity profile is assumed to be parabolic in the direction normal to the mid‐plane, so that one element along the width of the mould is enough to reproduce this profile if this element is quadratic. The velocity is prescribed to zero on the upper and lower surfaces and the normal to the mid‐plane is also prescribed to zero. In the case of div‐stable elements, the pressure profile is prescribed to be constant along the width of the mould. This can be achieved by using as interpolation degrees of freedom the pressure values at the element centroid and its derivatives in the directions tangent and normal to the mid‐plane, and prescribing the latter to zero. No modifications are needed when stabilized formulations are employed. To advance in time the function used in the VOF technique, we use a constant velocity across the width of the mould, which is taken as the projection on the tangent plane of each element of the nodal velocities. This is needed in order to have mass conservation.
Abstract
In this work we present a finite element formulation to simulate the filling of thin moulds. The model has as starting point a 3‐D approach using either div‐stable elements, [...]
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The characteristic‐based‐split procedure: an efficient and accurate algorithm for fluid problems
O. Zienkiewicz, P. Nithiarasu, R. Codina, M. Vázquez, P. Ortiz

Int. J. Numer. Meth. Fluids (1999). Vol. 31 (1), pp. 359-392

Abstract
In 1995 the two senior authors of the present paper introduced a new algorithm designed to replace the Taylor–Galerkin (or Lax–Wendroff) methods, used by them so far in the solution of compressible flow problems. The new algorithm was applicable to a wide variety of situations, including fully incompressible flows and shallow water equations, as well as supersonic and hypersonic situations, and has proved to be always at least as accurate as other algorithms currently used. The algorithm is based on the solution of conservation equations of fluid mechanics to avoid any possibility of spurious solutions that may otherwise result. The main aspect of the procedure is to split the equations into two parts, (1) a part that is a set of simple scalar equations of convective–diffusion type for which it is well known that the characteristic Galerkin procedure yields an optimal solution; and (2) the part where the equations are self‐adjoint and therefore discretized optimally by the Galerkin procedure. It is possible to solve both the first and second parts of the system explicitly, retaining there the time step limitations of the Taylor–Galerkin procedure. But it is also possible to use semi‐implicit processes where in the first part we use a much bigger time step generally governed by the Peclet number of the system while the second part is solved implicitly and is unconditionally stable. It turns out that the characteristic‐based‐split (CBS) process allows equal interpolation to be used for all system variables without difficulties when the incompressible or nearly incompressible stage is reached. It is hoped that the paper will help to make the algorithm more widely available and understood by the profession and that its advantages can be widely realised.
Abstract
In 1995 the two senior authors of the present paper introduced a new algorithm designed to replace the Taylor–Galerkin (or Lax–Wendroff) methods, used by them [...]
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Finite element implementation of two‐equation and algebraic stress turbulence models for steady incompressible flows
R. Codina, O. Soto

Int. J. Numer. Meth. Fluids (1999). Vol. 30 (3), 309-334

Abstract
The main purpose of this paper is to describe a finite element formulation for solving the equations for k and ε of the classical k–ε turbulence model, or any other two‐equation model. The finite element discretization is based on the SUPG method together with a discontinuity capturing technique to deal with sharp internal and boundary layers. The iterative strategy consists of several nested loops, the outermost being the linearization of the Navier–Stokes equations. The basic k–ε model is used for the implementation of an algebraic stress model that is able to account for the effects of rotation. Some numerical examples are presented in order to show the performance of the proposed scheme for simulating directly steady flows, without the need of reaching the steady state through a transient evolution.
Abstract
The main purpose of this paper is to describe a finite element formulation for solving the equations for k and ε of the classical k–ε [...]
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A fractional-step finite-element method for the Navier–Stokes equations applied to magma-chamber withdrawal
R. Folch, M. Vázquez, R. Codina, J. Martí i Castell

Computers and Geotechnics (1999). Vol. 25 (3), pp. 263-275

Abstract
We develop an algorithm to solve numerically the Navier–Stokes equations using a finite element method. The algorithm uses a fractional step approach that allows the use of equal interpolation spaces for the pressure and velocity fields and can be used to solve both compressible and incompressible flows. The standard Galerkin method is used to space-discretize the equations in which convective terms are dominant because the equations are reformulated in a characteristics co-moving frame providing thus the required artificial diffusion in a consistent way. The algorithm depends on four different parameters. Depending on their values, a fully implicit, a semi-implicit or a fully explicit solution can be obtained. The proposed algorithm may be useful in solving a wide spectrum of problems in geology, engineering and geosciences. Several flows frequently encountered in practical applications such as incompressible, slightly compressible or perfect gas are taken into account. As an example, we use it to model the withdrawal of magma from shallow chambers during explosive volcanic eruptions. Our model constitutes a first attempt to characterize the temporal evolution of the most revelant physical parameters during such a process.
Abstract
We develop an algorithm to solve numerically the Navier–Stokes equations using a finite element method. The algorithm uses a fractional step approach that allows [...]
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Numerical solution of the incompressible Navier–Stokes equations with Coriolis forces based on the discretization of the total time derivative.
R. Codina

Journal of Computational Physics (1999). Vol. 148 (2), pp. 467-496

Abstract
In this paper we present a numerical formulation to solve the incompressible Navier–Stokes equations written in a rotating frame of reference. The method is based on a finite difference discretization in time and a finite element discretization in space. When the viscosity is very small, numerical oscillations may appear due both to the high Reynolds number and to the presence of the Coriolis forces. To overcome these oscillations, a special discretization in time is proposed. The idea is to discretize the total time derivative in an inertial basis rather than only the partial time derivative in the rotating reference system. After this is done, a further high-order approximation is introduced, leading to a problem posed in the rotating frame of reference and in spatial coordinates. In contrast with the straightforward discretization of the original equations, some additional terms appear that enhance the stability of the numerical scheme. In the absence of Coriolis forces, the method is a generalization of the characteristic Galerkin technique for convection-dominated flows.
Abstract
In this paper we present a numerical formulation to solve the incompressible Navier–Stokes equations written in a rotating frame of reference. The method is based on [...]
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On the numerical modeling of frictional wear phenomena
C. Agelet de Saracibar, M. Chiumenti

Comput. Methods Appl. Mech. Engrg., (1999). Vol. 177 (3-4), pp. 401-426

Abstract
The evolution of the contact surfaces wear may become particularly important in the definition of the frictional behavior, in particular for frictional contact problems involving large slips, typically in sheet metal forming and bulk forming operations. Despite this fact, most of the current applications reported in the literature are restricted to a standard Coulomb law, using a constant friction coefficient. Such simple models may represent only a limited range of tribological situations and it appears to be necessary to develop a class of models which incorporate the state conditions and their evolution at the contact surfaces, taking into account the influence of complex phenomena such as wear, lubrication and chemical reactions, among others, see Oden and Martins [1]. In this paper a simple numerical model for the simulation of frictional wear behavior, within a fully nonlinear setting, including large slip and finite deformation, is presented. The model relies on the introduction of an internal variable related to the state conditions at the contact surface. Here, two possible definitions of this internal variable have been considered. The fully nonlinear frictional contact formulation, entirely derived first on a continuum setting by Laursen and Simo [2–6], has been extended here to accomodate the characterization of the wear frictional behavior. Within the computational aspects, two families of robust time stepping algorithms, arising from an operator split of the constrained frictional evolution equations, are discussed. Finally, following current approaches, see Lassen [9], Lassen and Bay [10], Owen et al. [11], de Souza et al. [12], Stromberg et al. [13] and Stromberg [14], a long-term tools wear prediction is given by introducing an a priori wear estimate derived from Archard's law, Archard [15]. The numerical model has been implemented into a enhanced version of the computational finite element program FEAP. Numerical examples show the suitability of the proposed model to capture the essential features of the frictional behavior at the contact interfaces and to provide a prediction of tool wear in forming operations.
Abstract
The evolution of the contact surfaces wear may become particularly important in the definition of the frictional behavior, in particular for frictional contact problems involving [...]
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Structural shape sensitivity analysis for nonlinear material models with strain softening
G. Bugeda, L. Gil, E. Oñate

Structural Optimization (1999). Vol. 17 (2-3), pp. 162-171

Abstract
This paper describes some considerations around the analytical structural shape sensitivity analysis when the structural behaviour is computed using the finite element method with a nonlinear constitutive material model. Traditionally, the structural sensitivity analysis is computed using an incremental approach based on the incremental procedures for the solution of the structural equilibrium problem. In this work, a direct (nonincremental) formulation for computing these structural sensitivities, that is valid for some specific nonlinear material models, is proposed. The material models for which the presented approach is valid are characterized by the fact that the stresses at any timet can be expressed in terms of the strains at the timet and, in some cases, the strains at a specific past timet u (t u<t). This is the case of elasticity (linear as well as nonlinear), perfect plasticity and damage models. A special strategy is also proposed for material models with strain softening. For the cases where it is applicable, the sensitivity analysis proposed here allows us to compute the structural sensitivities around any structural equilibrium point after finishing the solution process and it is completely independent of the numerical scheme used to solve the structural equilibrium problem. This possibility is particularized for the case of a damage model considering a strain-softening behaviour. Finally, the quality and reliability of the proposed approach is assessed through its application to some example
Abstract
This paper describes some considerations around the analytical structural shape sensitivity analysis when the structural behaviour is computed using the finite element method [...]
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A general procedure for deriving stabilized space–time finite element methods for advective–diffusive problems
E. Oñate, M. Manzán

Int. J. Numer. Meth. Fluids (1999). Vol. 31 (1), pp. 203-221

Abstract
A procedure to derive stabilized space–time finite element methods for advective–diffusive problems is presented. The starting point is the stabilized balance equation for the transient case derived by Oñate [Comput. Methods Appl. Mech. Eng., 151, 233–267 (1998)] using a finite increment calculus approach. A description of the new stabilization method and a procedure for computing the stabilization parameter of the space–time solution is given. The efficiency of the stabilization approach is shown in the solution of some transient advective–diffusive problems, including the non‐linear Burger's equation.
Abstract
A procedure to derive stabilized space–time finite element methods for advective–diffusive problems is presented. The starting point is the stabilized balance [...]
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Optimum aerodynamic shape design for fluid flow problems including mesh adaptivity
G. Bugeda, E. Oñate

Int. J. Numer. Meth. Fluids (1999). Vol. 30 (2), pp. 161-178

Abstract
This paper presents a methodology for solving shape optimization problems in the context of fluid flow problems including adaptive remeshing. The method is based on the computation of the sensitivities of the geometrical design parameters, the mesh, the flow variables and the error estimator to project the refinement parameters from one design to the next. The efficiency of the proposed method is checked out in two 2D optimization problems using a full potential model coupled with a boundary layer model. The first one corresponds to an internal flow problem and the second one corresponds to an external flow problem. The work presented here can be considered as a continuation of previous work (Bugeda and Oñate, Int. J. Numer. Methods Fluids, 20, 915–924 (1995)). In that paper, the sensitivity analysis corresponding to both an incompressible potential flow and a Euler flow were derived together with a strategy for the adaptive remeshing. In the present paper, the sensitivity analysis is derived for a full potential flow coupled with a boundary layer model, and a new error estimator is employed.
Abstract
This paper presents a methodology for solving shape optimization problems in the context of fluid flow problems including adaptive remeshing. The method is based on the computation [...]
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Thermo-Chemo-Mechanical Model for Concrete. II: Damage and Creep
M. Cervera, J. Oliver, T. Prato

Journal of Engineering Mechanics (1999). Vol. 125 (9), pp. 1028-1038

Abstract
In this work a coupled thermo-chemo-mechanical model for the behavior of concrete at early ages is proposed. This paper presents the formulation and assessment of the mechanical aspects of the model. Short- and long-term mechanical behaviors are modeled via a viscoelastic damage model that accounts for the aging effects. The short-term model is based on the framework of the continuum damage mechanics theory. A novel normalized format of the damage model is proposed, so that the phenomenon of aging is accounted for in a natural fashion. Long-term effects are included by incorporating a creep model inspired in the microprestress-solidification theory.
Abstract
In this work a coupled thermo-chemo-mechanical model for the behavior of concrete at early ages is proposed. This paper presents the formulation and assessment of the mechanical [...]
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Thermo-chemo-mechanical model for concrete. I: Hydration and aging
M. Cervera, T. Prato, J. Oliver

Journal of Engineering Mechanics (1999). Vol. 125 (9), pp. 1018-1027

Abstract
In this work a coupled thermo-chemo-mechanical model for the behavior of concrete at early ages is proposed. The model allows simulation of the observed phenomena of hydration, aging, damage, and creep. It is formulated within an appropriate thermodynamic framework, from which the state equations are derived. In this first part, the formulation and assessment of the thermochemical aspects of the model are presented. It is based on the reactive porous media theory, and it can accurately predict the evolution in time of the hydration degree and the hydration heat production. The evolution of the compressive and tensile strengths and elastic moduli is related to the aging degree, a concept introduced to account for the effect of the curing temperature in the evolution of the mechanical properties. The short- and long-term mechanical behavior is modeled by means of a viscoelastic damage model that accounts for the aging effects. The formulation and assessment of the mechanical part of the model are relegated to a companion paper.
Abstract
In this work a coupled thermo-chemo-mechanical model for the behavior of concrete at early ages is proposed. The model allows simulation of the observed phenomena of hydration, [...]
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Strong discontinuities and continuum plasticity models: the strong discontinuity approach
M. Cervera, O. Manzoli, J. Oliver

International Journal of Plasticity (1999). Vol. 15 (3), pp. 319-351

Abstract
The paper presents the Strong Discontinuity Approach for the analysis and simulation of strong discontinuities in solids using continuum plasticity models. Kinematics of weak and strong discontinuities are discussed, and a regularized kinematic state of discontinuity is proposed as a mean to model the formation of a strong discontinuity as the collapsed state of a weak discontinuity (with a characteristic bandwidth) induced by a bifurcation of the stress–strain field, which propagates in the solid domain. The analysis of the conditions to induce the bifurcation provides a critical value for the bandwidth at the onset of the weak discontinuity and the direction of propagation. Then a variable bandwidth model is proposed to characterize the transition between the weak and strong discontinuity regimes. Several aspects related to the continuum and, their associated, discrete constitutive equations, the expended power in the formation of the discontinuity and relevant computational details related to the finite element simulations are also discussed. Finally, some representative numerical simulations are shown to illustrate the proposed approach.
Abstract
The paper presents the Strong Discontinuity Approach for the analysis and simulation of strong discontinuities in solids using continuum plasticity models. Kinematics [...]
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On the formulation of coupled thermoplastic problems with phase-change
C. Agelet de Saracibar, M. Cervera, M. Chiumenti

International Journal of Plasticity (1999). Vol. 15 (1), pp. 1-34

Abstract
This paper deals with a numerical formulation for coupled thermoplastic problems including phase-change phenomena. The final goal is to get an accurate, efficient and robust numerical model, allowing the numerical simulation of solidification processes in the metal casting industry. Some of the current issues addressed in the paper are the following. A fractional step method arising from an operator split of the governing differential equations has been used to solve the nonlinear coupled system of equations, leading to a staggered product formula solution algorithm. Nonlinear stability issues are discussed and isentropic and isothermal operator splits are formulated. Within the isentropic split, a strong operator split design constraint is introduced, by requiring that the elastic and plastic entropy, as well as the phase-change induced elastic entropy due to the latent heat, remain fixed in the mechanical problem. The formulation of the model has been consistently derived within a thermodynamic framework. The constitutive behavior has been defined by a thermoelastoplastic free energy function, including a thermal multiphase change contribution. Plastic response has been modeled by a J2 temperature dependent model, including plastic hardening and thermal softening. A brief summary of the thermomechanical frictional contact model is included. The numerical model has been implemented into the computational Finite Element code COMET developed by the authors. A numerical assessment of the isentropic and isothermal operator splits, regarding the nonlinear stability behavior, has been performed for weakly and strongly coupled thermomechanical problems. Numerical simulations of solidification processes show the performance of the computational model developed.
Abstract
This paper deals with a numerical formulation for coupled thermoplastic problems including phase-change phenomena. The final goal is to get an accurate, efficient and robust [...]
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Numerical prediction of temperature and density distributions in selective laser sintering processes
G. Bugeda, M. Cervera, G. Lombera

Rapid Prototyping Journal (1999). Vol. 5 (1), pp. 21-26

Abstract
A finite element model has been developed for the 3D simulation of the sintering of a single track during a selective laser sintering process (SLS). The model takes into account both the thermal and the sintering phenomena involved in the process. Owing to the continuous movement of the laser beam the model takes also into account the transient nature of the problem. This is transformed into a pseudo‐static one through a transformation of the coordinates system of the equations. Nevertheless, this transformation introduces a convective term into the heat equations that produces instabilities in the solution. These instabilities have been solved by using a stream upwind Petrov Galerkin (SUPG) strategy together with a shock capturing scheme. Finally, a fixed point strategy is used for the solution of the analysis. The model has been tested through the solution of some examples.
Abstract
A finite element model has been developed for the 3D simulation of the sintering of a single track during a selective laser sintering process (SLS). The model takes into account [...]
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Thermo‐mechanical analysis of industrial solidification processes
M. Cervera, C. Agelet de Saracibar, M. Chiumenti

Int. J. Numer. Meth. Engng. (1999). Vol. 46 (9), pp. 1575-1591

Abstract
The paper presents an up‐to‐date finite element numerical model for fully coupled thermo‐mechanical problems, focussing in the simulation of solidification processes of industrial metal parts. The proposed constitutive model is defined by a thermo‐visco‐elasto‐(visco)plastic free energy function which includes a contribution for thermal multiphase changes. Mechanical and thermal properties are assumed to be temperature‐dependent, and viscous‐like strains are introduced to account for the variation of the elastic moduli during the cooling process. The continuous transition between the initial fluid‐like and the final solid‐like behaviour of the part is modelled by considering separate viscous and elasto‐plastic responses as a function of the solid fraction. Thermo‐mechanical contact conditions between the mould and the part are specifically considered, assuming that the heat flux is a function of the normal pressure and the thermal and mechanical gaps. A fractional step method arising from an operator split of the governing equations is used to solve the non‐linear coupled system of equations, leading to a staggered product formula solution algorithm suitable for large‐scale computations. Representative simulations of industrial solidification processes are shown, and comparison of computed results using the proposed model with available experimental data is given.
Abstract
The paper presents an up‐to‐date finite element numerical model for fully coupled thermo‐mechanical problems, focussing in the simulation of solidification processes [...]
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An unstructured grid-based, parallel free surface solver
R. Löhner, C. Yang, E. Oñate, S. Idelsohn

Applied Numerical Mathematics (1999). Vol. 31 (3), pp. 271-293

Abstract
An unstructured grid-based, parallel-free surface solver is presented. The overall scheme combines a finite-element, equal-order, projection-type 3-D incompressible flow solver with a finite element, 2-D advection equation solver for the free surface equation. For steady-state applications, the mesh is not moved every timestep, in order to reduce the cost of geometry recalculations and surface repositioning. A number of modifications required for efficient processing on shared-memory, cache-based parallel machines are discussed, and timings are shown that indicate scalability to a modest number of processors. The results show good quantitative comparison with experiments and the results of other techniques. The present combination of unstructured grids (enhanced geometrical flexibility) and good parallel performance (rapid turnaround) should make the present approach attractive to hydrodynamic design simulations.
Abstract
An unstructured grid-based, parallel-free surface solver is presented. The overall scheme combines a finite-element, equal-order, projection-type 3-D incompressible flow solver [...]
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A layer-wise triangle for analysis of laminated composite plates and shells
S. Botello, E. Oñate, J. Miquel

Computers and Structures (1999). Vol. 70 (6), pp. 635-646

Abstract
The paper presents a new triangle for analysis of laminate plates and shells. The in-plane degrees of freedom are interpolated quadratically whereas a linear layer-wise approximation is chosen for the normal displacement. A substructuring technique is used to eliminate the in-plane degrees of freedom during the assembly process thus reducing substantially the computationed costs. The element performance is evaluated in the static and dynamic analysis of dierent laminate plate and shell structures
Abstract
The paper presents a new triangle for analysis of laminate plates and shells. The in-plane degrees of freedom are interpolated quadratically whereas a linear layer-wise approximation [...]
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A mesh-free finite point method for advective-diffusive transport and fluid flow problems
E. Oñate, S. Idelsohn

Computational Mechanics (1998). Vol. 21 (4-5), pp. 283-292

Abstract
The finite point method (FPM) is a gridless numerical procedure based on the combination of weighted least square interpolations on a cloud of points with point collocation for evaluating the approximation integrals. In the paper, details of a procedure for stabilizing the numerical solution for advective-diffusive transport and fluid flow problems using the FPM are given. The method is based on a consistent introduction of the stabilizing terms in the governing differential equations. One example showing the applicability of the FPM is given.
Abstract
The finite point method (FPM) is a gridless numerical procedure based on the combination of weighted least square interpolations on a cloud of points with point collocation [...]
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A general procedure for deriving symmetric expressions for the secant and tangent stiffness matrices in finite element analysis
A. Morán, E. Oñate, J. Miquel

Int. J. Numer. Meth. Engng. (1998). Vol. 42 (2), pp. 219-236

Abstract
The paper presents a general and straightforward procedure based on the use of the strain energy density for deriving symmetric expressions of the secant and tangent stiffness matrices for finite element analysis of geometrically non‐linear structural problems. The analogy with previously proposed methods for deriving secant and tangent matrices is detailed. The simplicity of the approach is shown in an example of application
Abstract
The paper presents a general and straightforward procedure based on the use of the strain energy density for deriving symmetric expressions of the secant and tangent stiffness [...]
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A hierarchical finite element method based on the partition of unity
R. Taylor, O. Zienkiewicz, E. Oñate

Comput. Methods Appl. Mech. Engrg., (1998). Vol. 152, pp. 73-84

Abstract
In this paper we consider the application of hierarchical functions to base approximations which are a partition of unity. The particular hierarchical functions used are added to base finite element interpolations which, for Co approximations, are a particular case of the partition of unity. We also show how the functions may be constructed to preserve the interpolation property of the base finite element functions. An application to linear elasticity is used to illustrate the properties and stability of the approximation.
Abstract
In this paper we consider the application of hierarchical functions to base approximations which are a partition of unity. The particular hierarchical functions used are added [...]
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Derivation of stabilized equations for numerical solution of advective-diffusive transport and fluid flow problems
E. Oñate

Comput. Methods Appl. Mech. Engrg., (1998). Vol. 151 (1-2), pp. 233-265

Abstract
The concept of the so called “artificial or balancing diffusion” used to stabilize the numerical solution of advective–diffusive transport and fluid flow problems is revised in this paper. It is shown that the standard forms of the balancing diffusion terms, usually chosen in a heuristic manner, can be naturally found by introducing higher order approximations in the derivation of the governing differential equations via standard conservation (or equilibrium) principles. This allows us to reinterprete many stabilization algorithms and concepts used in every day practice by numerical analysts and also provides an expression for computing the stabilization parameter.
Abstract
The concept of the so called “artificial or balancing diffusion” used to stabilize the numerical solution of advective–diffusive transport and fluid flow [...]
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ED-Elas2D: An Educational Program for Computer-aided Training in Structural Analysis Using the Finite Element Method
B. Suarez, E. Blanco, L. Gil, P. Zapata, E. Oñate

European Journal of Engineering Education (1998). Vol. 23 (2), pp. 243-254

Abstract
In this paper, a methodology for computer-aided training of structural problems by the finite element method is presented. The resulting educational program, named ED-Elas2D, has been developed by a group of researchers at the School of Civil Engineering at the Technical University of Catalonia (UPC) in Barcelona, UPC. The program combines the standard concept which appears in the traditional teaching of finite element methods for structural analysis, such as the introduction to the basic structural theory, data definition (pre-processor), description of the analysis procedure (processor) and interpretation of results (post-processor). The program is addressed to both students who enrol in the study on finite element methods and to academic and technical staff in universities and companies who wish to update their knowledge of finite element techniques. The educational program ED-Elas2D works in the Windows system and it is characterized by its interactivity and graphic utilities.
Abstract
In this paper, a methodology for computer-aided training of structural problems by the finite element method is presented. The resulting educational program, named ED-Elas2D, [...]
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A posteriori error estimation for standard finite element analysis
P. Díez, J. Egozcue, A. Huerta

Comput. Methods Appl. Mech. Engrg., (1998). Vol. 163 (1-4), pp. 141-157

Abstract
A new residual type estimator based on projections of the error on subspaces of locally-supported functions is presented. The estimator is defined by a standard element-by-element refinement. First, an approximation of the energy norm of the error is obtained solving local problems with homogeneous Dirichlet boundary conditions. A later enrichment of the estimation is performed by adding the contributions of projections on a new family of subspaces. This estimate is a lower bound of the measure of the actual error. The estimator does not need to approximate local boundary conditions for the error equation. Therefore, computation of flux jumps is not necessary. Moreover, the estimator can be applied in mixed meshes containing elements of different shapes and its implementation in a standard finite element code is straightforward. The presented results show the effectiveness of the estimator approximating both the distribution and the global measure of the error, as well as its usefulness in adaptive procedures.
Abstract
A new residual type estimator based on projections of the error on subspaces of locally-supported functions is presented. The estimator is defined by a standard element-by-element [...]
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Shock capturing viscosities for the general fluid mechanics algorithm
P. Nithiarasu, O. Zienkiewicz, B. Sai, K. Morgan, R. Codina, M. Vázquez

Int. J. Numer. Meth. Fluids (1998). Vol. 28 (9), pp. 1325-1353

Abstract
The performance of different shock capturing viscosities has been examined using our general fluid mechanics algorithm. Four different schemes have been tested, both for viscous and inviscid compressible flow problems. Results show that the methods based on the second gradient of pressure give better performance in all situations. For instance, the method constructed from the nodal pressure values and consistent and lumped mass matrices is an excellent choice for inviscid problems. The method based on L2 projection is better than any other method in viscous flow computations. The residual based anisotropic method gives excellent performance in the supersonic range and gives better results in the hypersonic regime if a small amount of residual smoothing is used
Abstract
The performance of different shock capturing viscosities has been examined using our general fluid mechanics algorithm. Four different schemes have been tested, both for viscous [...]
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A fractional-step method for the incompressible navier-stokes equations related to a predictor-multicorrector algorithm
J. Blasco, R. Codina, A. Huerta

Int. J. Numer. Meth. Fluids (1998). Vol. 28 (10), pp. 1391-1419

Abstract
An implicit fractional-step method for the numerical solution of the time-dependent incompressible Naiver-Stokes equations in primitive variables is developed and studied in this paper. The method, which is first order accurate in the time-step, is shown to convergence to an exact solution of the equations. By adequately splitting the viscous term, it allows to enforce full Dirichlet boundary conditions on the velocity in all substeps of the scheme, while needing no boundary condition at all for the pressure. It is also shown to be related to an iterative predictor-multicorrector algorithm for evolution equations, when this is applied to the incompressible Naiver-Stokes system. A new derivation of the algorithm in a general setting is provided. Two different finite element interpolations are considered for the implementation of the algorithm; numerical results obtained with them for standard benchmark cases are presented.
Abstract
An implicit fractional-step method for the numerical solution of the time-dependent incompressible Naiver-Stokes equations in primitive variables is developed and studied [...]
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Comparison of some finite element methods for solving the diffusion-convection-reaction equation
R. Codina

Comput. Methods Appl. Mech. Engrg., (1998). Vol. 156, (1-4), pp. 185-210

Abstract
In this paper we describe several finite element methods for solving the diffusion-convection-reaction equation. None of them is new, although the presentation is non-standard in an effort to emphasize the similarities and differences between them. In particular, it is shown that the classical SUPG method is very similar to an explicit version of the Characteristic-Galerkin method, whereas the Taylor-Galerkin method has a stabilization effect similar to a sub-grid scale model, which is un turn related to the introduction of bubbles functions.
Abstract
In this paper we describe several finite element methods for solving the diffusion-convection-reaction equation. None of them is new, although the presentation is non-standard [...]
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A general algorithm for compressible and incompressible flows. Part III: The semi‐implicit form
R. Codina, M. Vázquez, O. Zienkiewicz

Int. J. Numer. Meth. Fluids (1998). Vol. 27 (1-4), 13-32

Abstract
In this paper we consider some particular aspects related to the semi‐implicit version of a fractional step finite element method for compressible flows that we have developed recently. The first is the imposition of boundary conditions. We show that no boundary conditions at all need to be imposed in the first step where an intermediate momentum is computed. This allows us to impose the real boundary conditions for the pressure, a point that turns out to be very important for compressible flows. The main difficulty of the semi‐implicit form of the scheme arises in the solution of the continuity equation, since it involves both the density and the pressure. These two variables can be related through the equation of state, which in turn introduces the temperature as a variable in many cases. We discuss here the choice of variables (pressure or density) and some strategies to solve the continuity equation. The final point that we study is the behaviour of the scheme in the incompressible limit. It is shown that the method has an inherent pressure dissipation that allows us to reach this limit without having to satisfy the classical compatibility conditions for the interpolation of the velocity and the pressure
Abstract
In this paper we consider some particular aspects related to the semi‐implicit version of a fractional step finite element method for compressible flows that we have developed [...]
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A numerical model for temporal variations during explosive central vent eruptions
A. Folch, J. Marti, R. Codina, M. Vázquez

Journal of Geophysical Research: Solid Earth (1998). Vol. 103, 20883-20899

Abstract
An axisymmetrical numerical model has been developed in order to find the temporal evolution of pressure, the position of the exsolution level, the velocity field, the eruption rate, and the amount of erupted material of a shallow, volatile‐rich, felsic magma chamber during a Plinian central vent eruption. The overpressure necessary to trigger the eruption is assumed to result from crystallization‐driven volatile oversaturation. We solve the resulting set of equations using a finite element method. The results obtained show that the pressure at the conduit entrance decreases exponentially as the eruption proceeds. This produces a shifting of the exsolution level, so that deeper parts of the chamber become progressively volatile oversaturated during the eruption. We assess the influence of chamber geometry and the physical properties of the magma on the computed parameters using several numerical examples. The results are also compared with those predicted by previous models from the literature and are found to be in good agreement with documented eruptions. The model constitutes a first attempt to numerically model the dynamics and the temporal evolution of the most relevant physical parameters during withdrawal from a closed magma chamber.
Abstract
An axisymmetrical numerical model has been developed in order to find the temporal evolution of pressure, the position of the exsolution level, the velocity field, the eruption [...]
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Numerical analysis of coupled thermomechanical frictional contact problems. Computational model and applications
C. Agelet de Saracibar

Archives of Comp. Meths. Engng. (1998). Vol. 5 (3), pp. 243-301

Abstract
In this paper a numerical model for the analysis of coupled thermomechanical multi-body frictional contact problems at finite deformations is presented. The multi-body frictional contact formulation is fully developed on the continuum setting and then a spatial (Galerkin projection) and temporal (time-stepping algorithm) discretization is applied. A contact pressure and temperature dependent thermal contact model has been used. A fractional step method arising from an operator split of the governing equations has been used to solve the coupled nonlinear system of equations, leading to a staggered solution algorithm. The numerical model has been implemented into an enhanced version of the computational finite element program FEAP. Numerical examples and simulation of industrial metal forming processes show the performance of the numerical model in the analysis of coupled thermomechanical frictional contact problems.
Abstract
In this paper a numerical model for the analysis of coupled thermomechanical multi-body frictional contact problems at finite deformations is presented. The multi-body frictional [...]
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A strain-based plastic viscous-damage model for massive concrete structures
R. Faria, M. Cervera, J. Oliver

Int. J. Solids and Structures (1998). Vol. 35 (14), pp. 1533-1558

Abstract
Within the framework of continuum damage mechanics, a new constitutive damage model for massive concrete is presented, mainly intended for the seismic analysis of gravity and arch dams. Consistent with thermodynamic requirements, a straindriven formalism is adopted, improving the algorithmic efficiency as much as required for the analysis of large scale problems to become feasible. Two scalar damage variables are introduced as internal variables, as well as a plastic-strain tensor. An extension to account for the concrete strain-rate dependency, suitable for seismic analysis, is presented at the end. The efficiency of numerical predictions from the constitutive model is illustrated through numerical applications and algorithmic implementation is also detailed.
Abstract
Within the framework of continuum damage mechanics, a new constitutive damage model for massive concrete is presented, mainly intended for the seismic analysis of gravity [...]
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Algebraic Discrete Nonlocal (DNL) Absorbing Boundary Condition for the Ship Wave Resistance Problem
M. Storti, J. D'ELIA, S. Idelsohn

Journal of Computational Physics (1998). Vol. 146 (2), pp 570-602

Abstract
An absorbing boundary condition for the ship wave resistance problem is presented. In contrast to the Dawson-like methods, it avoids the use of numerical viscosities in the discretization, so that a centered scheme can be used for the free surface operator. The absorbing boundary condition is “completely absorbing,” in the sense that the solution is independent of the position of the downstream boundary and is derived from straightforward analysis of the resulting constant-coefficients difference equations, assuming that the mesh is 1D-structured (in the longitudinal direction) and requires the eigen-decomposition of a matrix one dimension lower than the system matrix. The use of a centered scheme for the free surface operator allows a full finite element discretization. The drag is computed by a momentum flux balance. This method is more accurate and guarantees positive resistances.
Abstract
An absorbing boundary condition for the ship wave resistance problem is presented. In contrast to the Dawson-like methods, it avoids the use of numerical viscosities in the [...]
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Application of explicit FE codes to simulation of sheet and bulk metal forming processes
J. Rojek, E. Oñate, E. Postek

Journal of Materials Processing Technology (1998). Vols. 80-81, pp. 620-627

Abstract
This paper presents the application of an explicit dynamic finite element code for simulation of metal forming processes, of both sheet and bulk forming. The experiences reported here have been gained during the development and use of our own explicit program Stampack. An original formulation of a triangular shell element without rotational degrees of freedom is reviewed combining the explicit sheet forming simulation with the implicit springback analysis as well as the parallelization of the explicit program described. An extension of a finite element code for coupled thermomechanical analysis is discussed. A new thermomechanical constitutive model developed by the authors and implemented in the program is presented. Numerical examples illustrate some of the possibilities of the finite element code developed.
Abstract
This paper presents the application of an explicit dynamic finite element code for simulation of metal forming processes, of both sheet and bulk forming. The experiences [...]
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An advancing front point generation technique
R. Löhner, E. Oñate

Commun. Numer. Meth. Engng (1998). Vol. 14 (12), pp. 1097-1108

Abstract
An algorithm to construct boundary‐conforming, isotropic clouds of points with variable density in space is described. The input required consists of a specified mean point distance and an initial triangulation of the surface. Borrowing a key concept from advancing front grid generators, one point at a time is removed and, if possible, surrounded by admissible new points. This operation is repeated until no active points are left. Timings show that the scheme is about an order of magnitude faster than volume grid generators based on the advancing front technique, making it possible to generate large (>106) yet optimal clouds of points in a matter of minutes on a workstation. Several examples are included that demonstrate the capabilities of the technique.
Abstract
An algorithm to construct boundary‐conforming, isotropic clouds of points with variable density in space is described. The input required consists of a specified mean point [...]
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A finite element formulation for incompressible flow problems using a generalized streamline operator
M. Cruchaga, E. Oñate

Comput. Methods Appl. Mech. Engrg., (1997). Vol. 143, pp. 49-67

Abstract
A finite element formulation for solving incompressible flow problems is presented. In this paper, the generalized streamline operator presented by Hughes et al. (Comput. Methods Appl. Mech. Engrg. (1986) 58 305-328) for compressible flows is adapted to the incompressible Navier-Stokes equations. This new methodology allows the use of equal order interpolation for the unknowns of the problem: velocity and pressure. In this context, the definition of the ‘upwinding tensor’ does not require parameters defined outside this model. This formulation has been checked in classical tests with satisfactory results. Finally, a moving surface problem (Cruchaga et al., Comput. Numer. Methods Engrg. (1986) 59: 85-99) is also presented.
Abstract
A finite element formulation for solving incompressible flow problems is presented. In this paper, the generalized streamline operator presented by Hughes et al. (Comput. [...]
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Vulnerabilidad sísmica y toma de decisiones
J. Egozcue, G. Grande, P. Diez

Revista Internacional de Cálculo de Estructuras (1997). Vol. 2 (1), pp. 35-58

Abstract
Vulnerability of civil structures and systems under seismic actions have been extensively used and studied in the last decade. However, the goals of those studies are very diverse and it have caused some confusion on the meaning and definition of vulnerability. Naturally, different scopes of vulnerability lead to different methodologies in its study which may be incompatible. The present aim is to analyse the definition of seismic vulnerability in the framework of Bayesian decision making. Three different examples of decision making related to seismic vulnerability, which are qualitatively different, guide the discussion. They have an increasing complexity: decisions on normative seismic design; decisions on insurances against seismic risk and, finally, those decisions that should be taken to lead alarm, mitigation and rescue systems for seismic disasters. The three analised examples correspond to three different decision making schemes, respectively named: a priori, a posteriori and preposterior. In each case the definition of seismic vulnerability depends on the concept of considered utility (cost-benefit), on the involved random states and the scale in which the phenomena are to be considered. Most of the concepts associated with seismic vulnerability are reviewed through these three examples. A conclusion is that seismic vulnerability studies should consider the associated decision making problem. Simultaneously, the study of methodological and estimation aspects on vulnerability are remarked in order to improve both guidelines for seismic design and disaster mitigation.
Abstract
Vulnerability of civil structures and systems under seismic actions have been extensively used and studied in the last decade. However, the goals of those studies are very [...]
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Finite element solution of the Stokes problem with dominating Coriolis force
R. Codina, O. Soto

Comput. Methods Appl. Mech. Engrg., (1997). Vol. 142 (3-4), pp. 215-234

Abstract
The objective of this paper is to present a finite element formulation to solve the Stokes problem with Coriolis force. This force results in a skew-symmetric term in the weak formulation of the problem that deteriorates the stability of the standard Galerkin finite element method when the viscosity is small. We show that the stability is worsened due to the presence of the pressure gradient to enforce the incompressibility of the flow. The relevance of this effect depends on the relative importance of the viscous force and the Coriolis force, which is measured by the Ekman number. When it is small, oscillations occur using the Galerkin approach. To overcome them, we propose two different methods based on a consistent modification of the basic Galerkin formulation. Both methods eliminate the oscillations, keeping the accuracy of the formulation and enhancing its numerical stability.
Abstract
The objective of this paper is to present a finite element formulation to solve the Stokes problem with Coriolis force. This force results in a skew-symmetric term in the [...]
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A finite element formulation for Stokes proble allowing equal velocity-pressure interpolation
R. Codina, J. Blasco

Comput. Methods Appl. Mech. Engrg., (1997). Vol. 143 (3–4), pp. 373-391

Abstract
In this paper we study a variational formulation of the Stokes problem that accommodates the use of equal velocity-pressure finite element interpolations. The motivation of this method relies on the analysis of a class of fractional-step methods for the Navier-Stokes equations for which it is known that equal interpolations yield good numerical results. The reason for this turns out to be the difference between two discrete Laplacian operators computed in a different manner. The formulation of the Stokes problem considered here aims to reproduce this effect. From the analysis of the finite element approximation of the problem we obtain stability and optimal error estimates using velocity-pressure interpolations satisfying of the standard formulation. In particular, this condition is fulfilled by the most common equal order interpolations.
Abstract
In this paper we study a variational formulation of the Stokes problem that accommodates the use of equal velocity-pressure finite element interpolations. The motivation of [...]
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A new frictional time integration algorithm for large slip multi-body frictional contact problems
C. Agelet de Saracibar

Comput. Methods Appl. Mech. Engrg., (1997). Vol. 142 (3-4), pp. 303-334

Abstract
In this paper a new frictional time integration algorithm suitable for large slip multibody frictional contact problems is presented. The algorithm is introduced within the simple context of a model problem: the sliding motion of a particle onto a rough surface. Time integration of frictional traction is performed introducing a new slip path parametrization, which is defined independently traction is performed introducing element parametrization used in the spatial triangularization. The key point of the algorithm is that now, in presence of large slips, problems associated with slip motions such that a full incremental slip path is not within a single surface element, are completed bypassed. Remarkably, the algorithm is defined on the solely basis of the unit outward normal field to the surface without any appeal to the underlying local surface finite element triangularization. Geometrically, the assumed slip path can be viewed as an approximation to the geodesic passing throughout the initial and final points of each incremental slip path. The algorithm is amenable to exact linearization and asymptotic quadratic rate of convergence can be achieved within a Newton-Raphson iterative solution scheme. The algorithm can easily be extended to large slip multi-body frictional contact problems, involving finite strains.
Abstract
In this paper a new frictional time integration algorithm suitable for large slip multibody frictional contact problems is presented. The algorithm is introduced within the [...]
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Boundary conditions for finite element simulations of convective flows with artificial boundaries
J. Heinrich, S. Idelsohn, E. Oñate, C. Vionnet

Int. J. Numer. Meth. Engng. (1996). Vol. 39 (6), pp. 1053-1071

Abstract
We examine the use of natural boundary conditions and conditions of the Sommerfeld type for finite element simulations of convective transport in viscous incompressible flows. We show that natural boundary conditions are superior in the sense that they always provide a correct boundary condition, as opposed to the Sommerfeld‐type conditions, which can lead to a singular formulation and a great loss of accuracy. For the Navier–Stokes equations, the natural boundary conditions must be combined with a simple method to eliminate perturbations on the pressure at the open boundary, which is the source of most errors.
Abstract
We examine the use of natural boundary conditions and conditions of the Sommerfeld type for finite element simulations of convective transport in viscous incompressible flows. [...]
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Petrov-Galerkin methods for the transient advective-diffusive equation with sharp gradients
S. Idelsohn, J. Heinrich, E. Oñate

Int. J. Numer. Meth. Engng. (1996). Vol. 39 (9), pp. 1455-1473

Abstract
A Petrov–Galerkin formulation based on two different perturbations to the weighting functions is presented. These perturbations stabilize the oscillations that are normally exhibited by the numerical solution of the transient advective–diffusive equation in the vicinity of sharp gradients produced by transient loads and boundary layers. The formulation may be written as a generalization of the Galerkin Least‐Square method.
Abstract
A Petrov–Galerkin formulation based on two different perturbations to the weighting functions is presented. These perturbations stabilize the oscillations that are normally [...]
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A critical displacement approach for predicting structural instability
E. Oñate, W. Matias

Comput. Methods Appl. Mech. Engrg., (1996). Vol. 134 (1-2), pp. 135-161

Abstract
A new technique for predicting structural instability points using the finite element method is presented. The approach is based on the estimation of the critical displacement pattern by writing an approximation of the tangent stiffness singularity condition at the instability point. The critical load is subsequently computed by using a secant load-displacement relationship. Details of this procedure are given together with explicit forms of the secant stiffness matrix for finite element analysis of solids and trusses. The accuracy and effectiveness of the method are clearly shown in a number of examples of two- and three-dimensional bar structures.
Abstract
A new technique for predicting structural instability points using the finite element method is presented. The approach is based on the estimation of the critical displacement [...]
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A stabilized finite point method for analysis of fluid mechanics problems
E. Oñate, S. Idelsohn, O. Zienkiewicz, R. Taylor, C. Sacco

Comput. Methods Appl. Mech. Engrg., (1996). Vol. 195, pp. 6750-6777

Abstract
flow type problems is presented. The method is based on the use of a weighted least square interpolation procedure together with point collocation for evaluating the approximation integrals. Some examples of application to convective trasport and compressible flow problems are presented.
Abstract
flow type problems is presented. The method is based on the use of a weighted least square interpolation procedure together with point collocation for evaluating the approximation [...]
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Split, characteristic based semi‐implicit algorithm for laminar/turbulent incompressible flows
O. Zienkiewicz, B. Sai, K. Morgan, R. Codina

Int. J. Numer. Meth. Fluids (1996). Vol. 23, 787-809

Abstract
In an earlier paper, Zienkiewicz and Codina (Int. j. numer. methods fluids, 20, 869–885 (1995)) presented a general algorithm for the solution of both compressible and incompressible Navier–Stokes equations. The algorithm, based on operator splitting, permits arbitrary interpolation functions to be used while avoiding the Babŭska–Brezzi restriction. In addition, its characteristic based approach introduces a form of rational dissipation. Zienkiewicz et al. (Int. j. numer. methods fluids, 20, 887–913 (1995)) presented the application of this algorithm in its fully explicit form to various inviscid compressible flow problems. They also presented two incompressible flow problems solved by the fully explicit form, employing a pseudo compressibility. The present work deals with the application of the above algorithm it its semi‐implicit form to some incompressible flow benchmark problems. Further, it extends the methodology to turbulent flows by employing both one, and two equation turbulence models. A comparison of results with earlier investigations is presented. Other issues addressed in this study include the effect of additional diffusion terms present in the scheme for both laminar and turbulent flow problems and some practical difficulties associated with local time stepping.
Abstract
In an earlier paper, Zienkiewicz and Codina (Int. j. numer. methods fluids, 20, 869–885 (1995)) presented a general algorithm for the solution of both compressible [...]
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A rate-dependent isotropic damage model for the seismic analysis of concrete dams
M. Cervera, O. Manzoli, J. Oliver

Engineering Computations (1996). Vol. 25 (9), pp. 987-1010.

Abstract
In this paper a rate‐dependent isotropic damage model developed for the numerical analysis of concrete dams subjected to seismic excitation is presented. The model is shown to incorporate two features essential for seismic analysis: stiffness degradation and stiffness recovery upon load reversals and strain‐rate sensitivity. The issue of mesh objectivity is addressed using the concept of the ‘characteristic length’ of the fracture zone, to show that both the softening modulus and the fluidity parameter must depend on it to provide consistent results as the computational mesh is refined. Some aspects of the numerical implementation of the model are also treated, to show that the model can be easily incorporated in any standard non‐linear finite element code. The application of the proposed model to the seismic analysis of a large gravity concrete dam shows that the structural response may vary significantly in terms of the development of damage. The inclusion of rate sensitivity is able to reproduce the experimental observation that the tensile peak strength of concrete can be increased up to 50 percent for the range of strain rates that appear in a structural safety analysis of a dam subjected to severe seismic actions.
Abstract
In this paper a rate‐dependent isotropic damage model developed for the numerical analysis of concrete dams subjected to seismic excitation is presented. The model is shown [...]
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On the computational efficiency and implementation of block-iterative algorithms for nonlinear coupled Problems
M. Cervera, R. Codina, M. Galindo

Engineering Computations (1996). Vol. 13 (6), pp. 4-30

Abstract
Outlines a general methodology for the solution of the system of algebraic equations arising from the discretization of the field equations governing coupled problems. Considers that this discrete problem is obtained from the finite element discretization in space and the finite difference discretization in time. Aims to preserve software modularity, to be able to use existing single field codes to solve more complex problems, and to exploit computer resources optimally, emulating parallel processing. To this end, deals with two well-known coupled problems of computational mechanics – the fluid-structure interaction problem and thermally-driven flows of incompressible fluids. Demonstrates the possibility of coupling the block-iterative loop with the nonlinearity of the problems through numerical experiments which suggest that even a mild nonlinearity drives the convergence rate of the complete iterative scheme, at least for the two problems considered here. Discusses the implementation of this alternative to the direct coupled solution, stating advantages and disadvantages. Explains also the need for online synchronized communication between the different codes used as is the description of the master code which will control the overall algorithm.
Abstract
Outlines a general methodology for the solution of the system of algebraic equations arising from the discretization of the field equations governing coupled problems. Considers [...]
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A finite point method in computational mechancis. Applications to convective transport and fluid flow.
E. Oñate, S. Idelsohn, O. Zienkiewicz, R. Taylor

Int. J. Numer. Meth. Engng. (1996). Vol. 39 (22), pp. 3839-3866

Abstract
The paper presents a fully meshless procedure fo solving partial differential equations. The approach termed generically the ‘finite point method’ is based on a weighted least square interpolation of point data and point collocation for evaluating the approximation integrals. Some examples showing the accuracy of the method for solution of adjoint and non‐self adjoint equations typical of convective‐diffusive transport and also to the analysis of compressible fluid mechanics problem are presented.
Abstract
The paper presents a fully meshless procedure fo solving partial differential equations. The approach termed generically the ‘finite point method’ is based on [...]
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Industrial applications of sheet stamping simulation using new finite element models
J. Rojek, J. Jovicevic, E. Oñate

Journal of Materials Processing Technology (1996). Vol. 60 (1-4), pp. 243-247

Abstract
The paper is aimed to present industrial applications of sheet stamping simulation using new finite element formulations developed in the International Center for Numerical Methods in Engineering in Barcelona. Theoretical formulation is briefly reviewed. Both continuum and shell elements have been considered. The new shell elements developed are based on a geometrically exact shell model treating the shell as one-director Cosserat surface. The formulation of the continuum elements employs the multiplicative decomposition of the deformation gradient tensor into its elastic and plastic parts. The new finite element models have been implemented in the in-house explicit dynamic code STAMPACK. A number of practical problems of sheet metalforming have been solved with the program. Some of the problems, namely stamping of a kitchen sink, hydraulic forming of an aeronautical part and stamping of a food can, have been presented in the paper. The examples give an idea of practical information that can be obtained from the computer simulation of a forming process. The results confirm a good behaviour of the formulation and program used in the industrial applications.
Abstract
The paper is aimed to present industrial applications of sheet stamping simulation using new finite element formulations developed in the International Center for Numerical [...]
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Mixing anisotropic formulation for analysis of composites
S. Oller, E. Oñate, J. Canet

Commun. Numer. Meth. Engng (1996). Vol. 12 (8), pp. 471-482

Abstract
A general constitutive model adequate for analysis of the thermomechanical response of composite materials is presented. The model is based on the mixture of the basic substances of the composite and allows the evaluation of the interdependence between the constitutive behaviour of different compounding materials. The behaviour of the each compound is modelled by a general anisotropic thermo‐elasto‐plastic model, termed the ‘base model’. The different base models for each compound are combined using mixing theory to simulate the behaviour of the multiphase material.
Abstract
A general constitutive model adequate for analysis of the thermomechanical response of composite materials is presented. The model is based on the mixture of the basic substances [...]
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A coupled thermomechanical model for the solidification of cast metals
D. Celentano, S. Oller, E. Oñate

Int. J. Solids and Structures (1996). Vol. 33 (5), pp. 647-673

Abstract
A coupled thermomechanical model to simulate solidification problems in casting is presented. The model is formulated from a phenomenological point of view using a general isotropic thermoelasto-plasticity theory. Generalized phase-change effects accounting for the different thermomechanical behaviour of the solidifying material during its evolution from liquid to solid have been considered. For this purpose, a phase-change function, plastic evolution equations and a temperature-dependent constitutive law have been defined. Full thermomechanical effects as well as variable thermal and mechanical boundary conditions are also taken into account. Particular details concerning the numerical implementation of the model are given, where special emphasis is devoted to the resulting highly non-linear fully coupled finite element equations. The behaviour of this formulation is studied first in a simple quenching problem. Finally, a cylindrical casting test problem including phase-change phenomena, temperature-dependent constitutive properties and contact effects is analysed. Numerical results are compared with laboratory measurements.
Abstract
A coupled thermomechanical model to simulate solidification problems in casting is presented. The model is formulated from a phenomenological point of view using a general [...]
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A plastic damage constitutive model for composite materials
S. Oller, E. Oñate, J. Canet, S. Botello

Int. J. Solids and Structures (1996). Vol. 33 (17), pp. 2501-2518

Abstract
In this paper a generalized elasto-plastic damage model for the analysis of multiphase frictional composite materials is presented. Details of the derivation of the secant and tangent constitutive equations are given. Mixing theory is used to insert the basic constitutive expressions for each substance on the multiphase composite solid. Details of the numerical implementation of the model into a general non-linear finite element solution scheme are presented. Some examples of linear and non-linear behaviour of composites are given.
Abstract
In this paper a generalized elasto-plastic damage model for the analysis of multiphase frictional composite materials is presented. Details of the derivation of the secant [...]
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A hygro-thermo-mechanical constitutive model for multiphase composite materials
S. Oller, E. Oñate

Int. J. Solids and Structures (1996). Vol. 33 (20-22), pp. 3179-3186

Abstract
The paper describes a hygro-thermo-mechanical constitutive model appropriate for numerical simulation of multiphase composite material behaviour. The theory is based on the mixture of the basic substances of the composite and allows to evaluate the inter-dependent behaviour between the different compounding constitutive models. The initial anisotropy of each compounding can be taken into account by means of a mapped isotropic plastic formulation. This is a generalization of classic isotropic plasticity theory applied to orthotropic or anisotropic materials. The basic assumption is the existence of a stress and strain real anisotropic spaces and the respective fictitious isotropic spaces where a mapped fictitious problem is solved. Those spaces are related by means of two fourth order transformation tensor. The combination of mixing theory and the mapped isotropic plastic approach provides a powerful constitutive framework for the numerical treatment of bulk-fiber composite materials.
Abstract
The paper describes a hygro-thermo-mechanical constitutive model appropriate for numerical simulation of multiphase composite material behaviour. The theory is based [...]
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On the derivation and possibilities of the secant stiffness matrix for non linear finite element analysis
E. Oñate

Computational Mechanics (1995). Vol. 15 (6), pp. 572-593

Abstract
In this paper the general non symmetric parametric form of the incremental secant stiffness matrix for non linear analysis of solids using the finite element metod is derived. A convenient symmetric expression for a particular value of the parameters is obtained. The geometrically non linear formulation is based on a Generalized Lagrangian approach. Detailed expressions of all the relevant matrices involved in the analysis of 3D solids are obtained. The possibilities of application of the secant stiffness matrix for non linear structural problems including stability, bifurcation and limit load analysis are also discussed. Examples of application are given for the non linear analysis of pin joined frames.
Abstract
In this paper the general non symmetric parametric form of the incremental secant stiffness matrix for non linear analysis of solids using the finite element metod is derived. [...]
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New assumed strain triangles for non linear shell analysis
F. Flores, E. Oñate, F. Zarate

Computational Mechanics (1995). Vol. 17 (1-2), pp. 107-114

Abstract
A comparison between new and existing triangular finite elements based on the shell theory proposed by Juan Carlos Simo and co-workers is presented. Particular emphasis is put on the description of new triangles which show a promising behaviour for linear and non linear shell analysis.
Abstract
A comparison between new and existing triangular finite elements based on the shell theory proposed by Juan Carlos Simo and co-workers is presented. Particular emphasis is [...]
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A general algorithm for compressible and incompressible flow—Part II. tests on the explicit form
O. Zienkiewicz, K. Morgan, B. Sai, R. Codina, M. Vasquez

Int. J. Numer. Meth. Fluids (1995). Vol. 20 (8-9), pp. 887-913

Abstract
The algorithm introduced in Part I of this paper is applied in its explicit form to a variety of problems in order to demonstrate its wide range of applicability and excellent performance. Examples range from nearly incompressible, viscous, flows through transonic applications to high speed flows with shocks. In most examples linear triangular elements are used in the finite element approximation, but some use of quadratic approximation, again in triangles, indicates satisfactory performance even in the case of severe shocks.
Abstract
The algorithm introduced in Part I of this paper is applied in its explicit form to a variety of problems in order to demonstrate its wide range of applicability and excellent [...]
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A general algorithm for compressible and incompressible flow—Part I. the split, characteristic‐based scheme
O. Zienkiewicz, R. Codina

Int. J. Numer. Meth. Fluids (1995). Vol. 20, 869-885

Abstract
The paper outlines the formulation of a novel algorithm which can be used for the solution of both compressible and incompressible Navier‐Stokes or Euler equations. Full incompressibility can be dealt with if the algorithm is used in its semi‐explicit form and its structure permits arbitrary interpolation functions to be used avoiding the Babuška‐Brezzi restriction. In a fully explicit version it introduces a rational form of balancing dissipation avoiding the use of arbitrary parameters and forms for this.
Abstract
The paper outlines the formulation of a novel algorithm which can be used for the solution of both compressible and incompressible Navier‐Stokes or Euler equations. Full [...]
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Optimum aerodynamic shape design including mesh adaptivity
G. Bugeda, E. Oñate

Int. J. Numer. Meth. Fluids (1995). Vol. 20 (8-9), pp. 915-934

Abstract
This paper presents a methodology for solving shape optimization problems in the context of fluid flow problems including adaptive remeshing. The method is based on the computation of the sensitivities of the geometrical design parameters, the mesh, the flow variables and the error estimator to project the refinement parameters from one design to the next. This sensitivity analysis is described for the incompressible potential equations and the Euler equations. The efficiency of the proposed method is checked by means of two 2D inverse problems.
Abstract
This paper presents a methodology for solving shape optimization problems in the context of fluid flow problems including adaptive remeshing. The method is based on the computation [...]
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Seismic evaluation of concrete dams via continuum damage models
M. Cervera, R. Faria, J. Oliver

Earthquake Engineering Structural Dynamics (1995). Vol. 24 (9), pp. 1125-1245

Abstract
In this paper a general methodology for the analysis of large concrete dams subjected to seismic excitation is outlined. It is valid both for gravity dams (2D representation) and arch dams (3D representation). The method allows for non‐linear material behaviour of the dam, ‘transparent fictitious boundaries’ for dealing properly with in‐coming and out‐going seismic waves, and an efficient procedure to deal with dam‐soil‐fluid interaction. The mechanical behaviour of concrete is modelled using an isotropic damage model which allows for tension and compression damage, and exhibits stiffness recovery upon load reversals. Emphasis is placed in the treatment of fluid‐structure interaction, regarding both formulation and efficiency aspects. A gravity dam and an arch dam are analysed subjected to artificially generated earthquakes of different intensities, and the results are used to study the degree of (un)safety of the dams.
Abstract
In this paper a general methodology for the analysis of large concrete dams subjected to seismic excitation is outlined. It is valid both for gravity dams (2D representation) [...]
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Numerical analysis of stereolithography processes using the finite element method
G. Bugeda, M. Cervera, G. Lombera, E. Oñate

Rapid Prototyping Journal (1995). Vol. 1 (2), pp. 13-23

Abstract
Stereolithography (SLA) is one of the most important techniques used in rapid prototyping processes. It has a great industrial interest because it allows for dramatic time savings with respect to traditional manufacturing processes. One of the main sources of error in the final dimensions of the prototype is the curl distortion effect owing to the shrinkage of the resin during the SLA process. Presents a study of the influence of different constructive and numerical parameters in the curl distortion, an analysis which was made using the computer code stereolithography analysis program, developed to model SLA processes using the finite element method. Also briefly presents this code.
Abstract
Stereolithography (SLA) is one of the most important techniques used in rapid prototyping processes. It has a great industrial interest because it allows for dramatic time [...]
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NUMISTAMP: a research project for assessment of finite-element models for stamping processes
E. Oñate, J. Rojek, C. Garino

Journal of Materials Processing Technology (1995). Vol. 50 (1-4), pp. 17-38

Abstract
This paper describes the objectives and current status of the research project NUMISTAMP currently under development at the International Center for Numerical Methods in Engineering of (CIMNE) located in Barcelona, Spain. The aim of this project is the assesment of different finite element models for simulation of sheet stamping processes. The models currently analyzed include: quasistatic viscoplastic flow and elastoplastic solid models and explicit dynamic models. Both shell and continuum elements are considered in most of these cases. The paper presents an overview of the basic features of the different models. Examples of application including some benchmark test cases proposed at NUMISHEET are also presented.
Abstract
This paper describes the objectives and current status of the research project NUMISTAMP currently under development at the International Center for Numerical Methods in Engineering [...]
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On the pseudomaterial approach for the analysis of transient forming processes
M. Cruchaga, E. Oñate, S. Idelsohn

Commun. Numer. Meth. Engng (1995). Vol. 11 (2), pp. 137-148

Abstract
A fixed‐mesh method for the analysis of transient forming processes is presented. The mesh covers material regions and zones through which the material may flow. These last zones are identified by a pseudomaterial with relatively small physical parameters. During time processing, the interface between both materials is followed by an arbitrary Lagrangian mesh. This technique appears to be suitable for the treatment of moving surfaces with sharp corners. A particular boundary condition for the Navier‐Stokes equations is also introduced in order to model a porous wall.
Abstract
A fixed‐mesh method for the analysis of transient forming processes is presented. The mesh covers material regions and zones through which the material may flow. These last [...]
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Numerical modelling and simulation of frictional contact using a generalised coulomb law
A. Heege, P. Alart, E. Oñate

Engineering Computations (1995). Vol. 12 (7), pp. 641-656

Abstract
A consistent formulation for unilateral contact problems including frictional work hardening or softening is proposed. The approach is based on an augmented Lagrangian approach coupled to an implicit quasi‐static Finite Element Method. Analogous to classical work hardening theory in elasto‐plasticity, the frictional work is chosen as the internal variable for formulating the evolution of the friction convex. In order to facilitate the implementation of a wide range of phenomenological models, the friction coefficient is defined in a parametrised form in terms of Bernstein polynomials. Numerical simulation of a 3D deep‐drawing operation demonstrates the performance of the methods for predicting frictional contact phenomena in the case of large sliding paths including high curvatures.
Abstract
A consistent formulation for unilateral contact problems including frictional work hardening or softening is proposed. The approach is based on an augmented Lagrangian approach [...]
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An anisotropic elastoplastic model based on an isotropic formulation
S. Oller, S. Botello, J. Canet, E. Oñate

Engineering Computations (1995). Vol. 12 (3), pp. 245-262

Abstract
This paper shows a generalization of the classic isotropic plasticity theory to be applied to orthotropic or anisotropic materials. This approach assumes the existence of a real anisotropic space, and other fictitious isotropic space where a mapped fictitious problem is solved. Both spaces are related by means of a linear transformation using a fourth order transformation tensor that contains all the information concerning the real anisotropic material. The paper describes the basis of the spaces transformation proposed and the expressions of the resulting secant and tangent constitutive equations. Also details of the numerical integration of the constitutive equation are provided. Examples of application showing the good performance of the model for analysis of orthotropic materials and fibre‐reinforced composites are given.
Abstract
This paper shows a generalization of the classic isotropic plasticity theory to be applied to orthotropic or anisotropic materials. This approach assumes the existence of [...]
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Finite volumes and finite elements: Two ‘good friends’
E. Oñate, S. Idelsohn

Int. J. Numer. Meth. Engng. (1994). Vol. 37 (19), pp. 3323-3341

Abstract
In this paper a comparison between the finite element and the finite volume methods is presented in the context of elliptic, convective–diffusion and fluid flow problems. The paper shows that both procedures share a number of features, like mesh discretization and approximation. Moreover, it is shown that in many cases both techniques are completely equivalent.
Abstract
In this paper a comparison between the finite element and the finite volume methods is presented in the context of elliptic, convective–diffusion and fluid flow problems. [...]
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A temperature‐based formulation for finite element analysis of generalized phase‐change problems
D. Celentano, E. Oñate, S. Oller

Int. J. Numer. Meth. Engng. (1994). Vol. 37 (20), pp. 3441-3465

Abstract
A finite element formulation for solving multidimensional phase‐change problems is presented. The formulation considers the temperature as the unique state variable, it is conservative in the weak form sense and it preserves the moving interface condition. In this work, an approximate jacobian matrix that preserves numerical convergence and stability is also derived. Furthermore, a comparative analysis with other different phase‐change finite element techniques is performed. Finally, several numerical examples are analysed in order to show the performance of the proposed methodology.
Abstract
A finite element formulation for solving multidimensional phase‐change problems is presented. The formulation considers the temperature as the unique state variable, it [...]
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A simple triangular element for thick and thin plate and shell analysis
E. Oñate, F. Zárate, F. flores

Int. J. Numer. Meth. Engng. (1994). Vol. 37 (15), pp. 2569-2582

Abstract
A new plate triangle based on Reissner–Mindlin plate theory is proposed. The element has a standard linear deflection field and an incompatible linear rotation field expressed in terms of the mid‐side rotations. Locking is avoided by introducing an assumed linear shear strain field based on the tangential shear strains at the mid‐sides. The element is free of spurious modes, satisfies the patch test and behaves correctly for thick and thin plate and shell situations. The element degenerates in an explicit manner to a simple discrete Kirchhoff form.
Abstract
A new plate triangle based on Reissner–Mindlin plate theory is proposed. The element has a standard linear deflection field and an incompatible linear rotation field [...]
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A finite volume format for structural mechanics
E. Oñate, M. Cervera, O. Zienkiewicz

Int. J. Numer. Meth. Engng. (1994). Vol. 37 (2), pp. 181-201

Abstract
A general Finite Volume Method (FVM) for the analysis of structural problems is presented. It is shown that the FVM can be considered to be a particular case of finite elements with a non‐Galerkin weighting. For structural analysis this can readily be interpreted as equivalent to the unit displacement method which involves mainly surface integrals. Both displacement and mixed FV formulations are presented for static and dynamic problems.
Abstract
A general Finite Volume Method (FVM) for the analysis of structural problems is presented. It is shown that the FVM can be considered to be a particular case of finite elements [...]
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A methodology for adaptive mesh refinement in optimum shape design problems
G. Bugeda, E. Oñate

Computing Systems in Engineering (1994). Vol. 5 (1), pp. 91-102

Abstract
This work presents a methodology based on the use of adaptive mesh refinement (AMR) techniques in the context of shape optimization problems analyzed by the Finite Element Method (FEM). A suitable and very general technique for the parametrization of the optimization problem using B-splines to define the boundary is first presented. Then, mesh generation using the advancing front method, the error estimation and the mesh refinement criteria are dealt with in the context of a shape optimization problems. In particular, the sensitivities of the different ingredients ruling the problem (B-splines, finite element mesh, design behaviour, and error estimator) are studied in detail. The sensitivities of the finite element mesh coordinates and the error estimator allow their projection from one design to the next, giving an “a priori knowledge” of the error distribution on the new design. This allows to build up a finite element mesh for the new design with a specified and controlled level of error. The robustness and reliability of the proposed methodology is checked out with some 2D examples.
Abstract
This work presents a methodology based on the use of adaptive mesh refinement (AMR) techniques in the context of shape optimization problems analyzed by the Finite Element [...]
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Mould filling simulation using finite elements
R. Codina, U. Schäfer, E. Oñate

Int. J. of Num. Meths. for Heat and Fluid Flow (1994). Vol. 4 (1), pp. 291-310

Abstract
In this paper we consider several aspects related to the application of the pseudo‐concentration techniques to the simulation of mould filling processes. We discuss, in particular, the smoothing of the front when finite elements with interior nodes are employed and the evacuation of air through the introduction of temporary free wall nodes. The basic numerical techniques to solve the incompressible Navier—Stokes equations are also briefly described. The main features of the numerical model are the use of div‐stable velocity—pressure interpolations with discontinuous pressures, the elimination of the pressure via an iterative penalty formulation, the use of the SUPG approach to deal with convection‐dominated problems and the temporal integration using the generalized trapezoidal rule. At the end of the paper we present some numerical results obtained for a two‐dimensional test problem showing the ability of the method to capture complicated flow patterns.
Abstract
In this paper we consider several aspects related to the application of the pseudo‐concentration techniques to the simulation of mould filling processes. We discuss, in [...]
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A penalty finite element method for non‐Newtonian creeping flows
R. Codina, M. Cervera, E. Oñate

Int. J. Numer. Meth. Engng. (1993). Vol. 36 (8), pp. 1395-1412

Abstract
In this paper we present an iterative penalty finite element method for viscous non‐Newtonian creeping flows. The basic idea is solving the equations for the difference between the exact solution and the solution obtained in the last iteration by the penalty method. For the case of Newtonian flows, one can show that for sufficiently small penalty parameters the iterates converge to the incompressible solution. The objective of the present work is to show that the iterative penalization can be coupled with the iterative scheme used to deal with the non‐linearity arising from the constitutive law of non‐Newtonian fluids. Some numerical experiments are conducted in order to assess the performance of the approach for fluids whose viscosity obeys the power law.
Abstract
In this paper we present an iterative penalty finite element method for viscous non‐Newtonian creeping flows. The basic idea is solving the equations for the difference [...]
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A finite element model for thermomechanical analysis in casting processes
D. Celentano, S. Oller, E. Oñate

Journal of Physique IV (1993). Vol. 3 (C7), pp. 1171-1180

Abstract
This paper summarizes the recent work of the authors in the numerical simulation of casting processes. In particular, a coupled thermomechanical model to simulate the solidification problem in casting has been developed [7,8,9]. The model, based on a general isotropic thermoelasto-plasticity theory and formulated in a macroscopical point of view, includes generalized phase-change effects and considers the different thermomechanical behaviour of the solidifying material during its evolution from liquid to solid. For this purpose, a phase-change variable, plastic evolution equations and a temperature-dependent material constitutive law have been defined. Some relevant aspects of this model are presented here. Full thermomechanical coupling terms have been considered as well as variable thermal and mechanical boundary conditions : the first are due to air gap formation, while the second involve a contact formulation. Particular details concerning the numerical implementation of this model are also mentioned. An enhanced staggered scheme, used to solve the highly non-linear fully coupled finite element equations, is proposed. Furthermore, a proper convergence criterion to stop the iteration process is adopted and, although the quadratic convergence of Newton-Rapshon's method is not achieved, several numerical experiments demonstrate reasonable convergence rates [9]. Finally, an experimental cylindrical casting test problem, including phase-change phenomena, temperature-dependent constitutive properties and contact effects, is analyzed. Numerical results are compared with some laboratory measurements.
Abstract
This paper summarizes the recent work of the authors in the numerical simulation of casting processes. In particular, a coupled thermomechanical model to simulate the solidification [...]
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A discontinuity-capturing crosswind-dissipation for the finite element solution of the convection-diffusion equation
R. Codina

Comput. Methods Appl. Mech. Engrg., (1993). Vol. 110 (3-4), pp. 325-342

Abstract
To avoid the local oscillations that still remain using the streamline-upwind/Petrov-Galerkin formulation for the scalar convection-diffusion equation, the introduction of a nonlinear crosswind dissipation is proposed. It is shown that the method is less overdiffusive than other discontinuity-capturing techniques and has better numerical behavior. The design of the crosswind diffusion is based on the study of the discrete maximum principle for some simple cases.
Abstract
To avoid the local oscillations that still remain using the streamline-upwind/Petrov-Galerkin formulation for the scalar convection-diffusion equation, the introduction of [...]
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Stability analysis of the forward Euler scheme for the convection‐diffusion equation using the SUPG formulation in space
R. Codina

Int. J. Numer. Meth. Engng. (1993). Vol. 36, 1445-1464

Abstract
The stability and accuracy of the forward Euler scheme for the semidiscrete problem arising from the space discretization of the convection‐diffusion equation using the SUPG formulation are analysed. Both linear and quadratic finite elements are considered. The stability limits are derived for the one‐dimensional problem and a heuristic criterion is proposed for the multidimensional equation. Some numerical experiments are conducted in order to assess the performance of different finite elements
Abstract
The stability and accuracy of the forward Euler scheme for the semidiscrete problem arising from the space discretization of the convection‐diffusion equation using the [...]
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An iterative penalty method for the finite element solution of the stationary Navier-Stokes equations
R. Codina

Comput. Methods Appl. Mech. Engrg., (1993). Vol. 110 (3-4), pp. 237-262

Abstract
The objective of this paper is to analyse an iterative procedure for the finite element solution of the Stokes and Navier-Stokes stationary problems. For the latter case, the usual condition on the viscosity and the data that ensures uniqueness is assumed. The method is based on the iterative imposition of the incompressibility condition via penalization. Theoretical and numerical results show that this constraint can be approximated iteratively within the same iterative loop used to deal with the nonlinear term of the equations. Two particular iterative schemes are analysed, namely those based on the Picard and Newton-Raphson algorithms.
Abstract
The objective of this paper is to analyse an iterative procedure for the finite element solution of the Stokes and Navier-Stokes stationary problems. For the latter case, [...]
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Derivation of thin plate bending elements with one degree of freedom per node: a simple three node triangle
E. Oñate, M. Cervera

Engineering Computations (1993). Vol. 10 (6), pp. 543-561

Abstract
A general methodology for deriving thin plate bending elements with a single degree of freedom per node is presented. The formulation is based on the combination of a standard C0 finite element interpolation for the deflection field with an independent approximation of the curvatures which are expressed in terms of the deflection gradient along the sides using a finite volume‐like approach. The formulation is particularized for the simplest element of the family, i.e. the three node triangle with three degrees of freedom. The potential of the new element is shown through different examples of application.
Abstract
A general methodology for deriving thin plate bending elements with a single degree of freedom per node is presented. The formulation is based on the combination of a standard C0 [...]
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A study of mesh optimality criteria in adaptive finite element analysis
E. Oñate, G. Bugeda

Engineering Computations (1993). Vol. 10 (4), pp. 307-321

Abstract
The concepts of solution error and optimal mesh in adaptive finite element analysis are revisited. It is shown that the correct evaluation of the convergence rate of the error norms involved in the error measure and the optimal mesh criteria chosen are essential to avoid oscillations in the refinement process. Two mesh optimality criteria based on: (a) the equal distribution of global error, and (b) the specific error over the elements are studied and compared in detail through some examples of application.
Abstract
The concepts of solution error and optimal mesh in adaptive finite element analysis are revisited. It is shown that the correct evaluation of the convergence rate of the error [...]
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A general methodology for deriving shear constrained Reissner-Mindlin plate elements
E. Oñate, O. Zienkiewicz, B. Suarez, R. Taylor

Int. J. Numer. Meth. Engng. (1992). Vol. 33 (2), pp. 345-367

Abstract
In this paper the necessary requirements for the good behaviour of shear constrained Reissner–Mindlin plate elements for thick and thin plate situations are re‐interpreted and a simple explicit form of the substitute shear strain matrix is obtained. This extends the previous work of the authors presented in References 18 and 31. The general methodology is applied to the re‐formulation of some well known quadrilateral plate elements and some new triangular and quadrilateral plate elements which show promising features. Some examples of the good behaviour of these elements are given.
Abstract
In this paper the necessary requirements for the good behaviour of shear constrained Reissner–Mindlin plate elements for thick and thin plate situations are re‐interpreted [...]
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The intrinsic time for the streamline upwind Petrov-Galerkin formulation using quadratic elements
R. Codina, E. Oñate, M. Cervera

Comput. Methods Appl. Mech. Engrg., (1992). Vol. 94, pp. 239-262

Abstract
In this paper the functions of the Péclet number that appear in the intrinsic time of the streamline upwind/Petrov-Galerkin (SUPG) formulation are analyzed for quadratic elements. Some related issues such as the computation of the characteristic element length and the introduction of source terms in the one-dimensional model problem are also addressed.
Abstract
In this paper the functions of the Péclet number that appear in the intrinsic time of the streamline upwind/Petrov-Galerkin (SUPG) formulation are analyzed for quadratic [...]
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Numerical Analysis of Dams with Extensive Cracking due to Concrete Hydration: Simulation of a Real Case
M. Cervera, M. Galindo, J. Oliver

Dam Engng. (1992). Vol. 3 (1), pp. 1-22.

Abstract
The paper presents the computational model developed to study an existing large gravity dam suffering from observed "pathological behavior" resulting concrete hydration. The combined effect of water intrusion and chemical and numerical studies. The present study was undertaken to simulate numerically the observed phenomenon and to predict future developments. Concrete is modelled using an isotropic continuum damage model including visco-elastic effects. The triggering of the volumetric expansion resulting from water intrusion is linked to the onset of damage at each a point, assuming that water enters dam mostly through the damaged areas. Transversal construction joints are modelled using smeared joints. Temperature and porewater pressure effects are included using assumed distributions based on available field data. Results are presented which match reasonably well with the available filed measurements.
Abstract
The paper presents the computational model developed to study an existing large gravity dam suffering from observed "pathological behavior" resulting concrete hydration. [...]
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Comparative study on sheet metal forming processes by numerical modelling and experiment
W. Sosnowski, E. Oñate, C. Agelet de Saracibar

Journal of Materials Processing Technology (1992). Vol. 34 (1-4), pp. 109-116

Abstract
In this paper some results of a wide experimental program are presented and compared with some finite element solution of sheet metal forming problems using a viscous shell formulation.
Abstract
In this paper some results of a wide experimental program are presented and compared with some finite element solution of sheet metal forming problems using a viscous shell [...]
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Finite element analysis of sheet metal forming problems using a selective viscous bending/membrane formulation
E. Oñate, C. Agelet de Saracibar

Int. J. Numer. Meth. Engng. (1990). Vol. 30 (8), pp. 1577-1593

Abstract
In this paper the possibilities of the viscous voided shell approach for deriving bending/membrane finite elements for sheet metal forming problems are presented. These elements can be selectively used for membrane or full bending analysis of some parts of the sheet according to the nature of the deformation. Numerical aspects of this approach are discussed and some examples of application are also given.
Abstract
In this paper the possibilities of the viscous voided shell approach for deriving bending/membrane finite elements for sheet metal forming problems are presented. These elements [...]
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Finite element nonlinear analysis of concrete structures using a “plastic-damage model”
S. Oller, E. Oñate, J. Oliver, J. Lubliner

Engineering Fracture Mechanics (1990). Vol. 35 (1-2-3), pp. 219-231

Abstract
In this paper a plastic damage model for nonlinear finite element analysis of concrete is presented. The model is based on standard plasticity theory for frictional materials. Details of the expressions of a new yield function proposed and of the evolution laws of the model parameters are given. The model allows to include elastic and plastic stiffness degradation effects. This is also discussed in the paper together with the problem of mesh objectivity, and the a posteriori determination of cracks. Finally, one example of application which shows the accuracy of the model is also given.
Abstract
In this paper a plastic damage model for nonlinear finite element analysis of concrete is presented. The model is based on standard plasticity theory for frictional [...]
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A computational model for progressive cracking in large dams due to the swelling of concrete
M. Cervera, J. Oliver, E. Herrero, E. Oñate

Engineering Fracture Mechanics (1990). Vol. 35 (1-3), pp. 573-585

Abstract
The paper presents a computational model for the analysis of large concrete gravity dams subjected to severe damage due to internal actions. It has been observed in several operating concrete dams that the combined effects of water intrusion and concrete expansion produce a time-advancing deteriorating process that may endanger the global stability of the construction. The present study was undertaken to simulate numerically the observed phenomena and to enable to predict future developments. Tensile cracking of the concrete is modelled using an elasticfracturing constitutive model. The model is able to simulate in a realistic manner the phenomena of primary and secondary crack initiation, elastic degradation, crack closing and reopening. The triggering of the volumetric expansion due to water intrusion is linked to the onset of cracking at each point, assuming that water enters the dam mostly through the cracks. Temperature and pore-water pressure effects are included using assumed distributions based on available field data. Construction joints are modelled using a frictional joint element, although a “constitutive alternative” is outlined. Close surveillance of the behaviour of a dam that presented this sort of problem was used to calibrate the numerical model and to confirm the obtained results.
Abstract
The paper presents a computational model for the analysis of large concrete gravity dams subjected to severe damage due to internal actions. It has been observed in several [...]
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Plate bending elements with discrete constraints: New triangular elements
O. Zienkiewicz, R. Taylor, P. Papadopoulos, E. Oñate

Computers and Structures (1990). Vol. 35 (4), pp. 505-522

Abstract
In recent years a series of elements based on Reissner-Mindlin assumptions and using discrete (collocation type) constraints has been introduced. These elements have proved to be very effective, however their relation to straightforward mixed approximations has not been clear. In this paper this relationship is discussed and the reasons for their success explained. This allows new and effective triangular elements to be developed. The presentation shows the close relationships with the DKT (Discrete Kirchhoff Theory) element previously available only for thin plates and allows extension of their applications.
Abstract
In recent years a series of elements based on Reissner-Mindlin assumptions and using discrete (collocation type) constraints has been introduced. These elements have [...]
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A plastic-damage model for concrete
J. Lubliner, J. Oliver, S. Oller, E. Oñate

Int. J. Solids and Structures (1989). Vol. 25 (3), pp. 299-326

Abstract
In this paper a constitutive model based on an internal variable-formulation of plasticity theory for the non-linear analysis of concrete is presented. The model uses a new yield criterion which matches experimental data quite well and it accounts for both elastic and plastic stiffness degradations effects. Onset and amount of cracking can be studied by a simple postprocessing of the finite-element plasticity solution. The accuracy of the model is checked with some examples of application.
Abstract
In this paper a constitutive model based on an internal variable-formulation of plasticity theory for the non-linear analysis of concrete is presented. The model uses a new [...]
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Dynamic analysis of structures using a Reissner-Mindlin finite strip formulation
J. Canet, B. Suarez, E. Oñate

Computers and Structures (1989). Vol. 31 (6), pp. 967-975

Abstract
In this paper a finite strip formulation based on Reissner-Mindlin plate theory for dynamic analysis of prismatic shell type structure is presented. Detailed expressions of the relevant strip matrices for a variety of structures using the simple two node linear strip element are given. Examples of the good performance of the linear strip element for free and forced vibration analysis of plates, bridges and axisymmetric shells are presented.
Abstract
In this paper a finite strip formulation based on Reissner-Mindlin plate theory for dynamic analysis of prismatic shell type structure is presented. Detailed expressions of [...]
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Plastic and viscoplastic flow of void‐containing metals. Applications to axisymmetric sheet forming problems
E. Oñate, M. Kleiber, C. Agelet de Saracibar

Int. J. Numer. Meth. Engng. (1988). Vol. 25 (1), pp. 227-251

Abstract
A formal analogy between the equations of pure plastic and viscoplastic flow theory for void‐containing metals and those of standard non‐linear elasticity is presented. The formulation is particularized for the analysis of axisymmetric sheet metal forming problems using simple two node linear finite elements. Details of the treatment of friction and strain hardening phenomena, time increment computation and elastic effects are also given. Examples of the effect of void porosity on the hemispherical stretching of a circular sheet are presented.
Abstract
A formal analogy between the equations of pure plastic and viscoplastic flow theory for void‐containing metals and those of standard non‐linear elasticity is presented. [...]
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On a non‐linear formulation for curved Timoshenko beam elements considering large displacement/rotation increments
E. Dvorkin, E. Oñate, J. Oliver

Int. J. Numer. Meth. Engng. (1988). Vol. 26 (7), pp. 1597-1613

Abstract
An incremental Total Lagrangian Formulation for curved beam elements that includes the effect of large rotation increments is developed. A complete and symmetric tangent stiffness matrix is obtained and the numerical results show, in general, an improvement over the standard formulation where the assumption of infinitesimal rotation increments is made in the derivation of the tangent stiffness matrix.
Abstract
An incremental Total Lagrangian Formulation for curved beam elements that includes the effect of large rotation increments is developed. A complete and symmetric tangent stiffness [...]
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Benchmarks for geotechnical modeling
E. Alarcón, E. Alonso, D. Aubry, K. Axelsson, E. Oñate

Int. J. Numer. Meth. Engng. (1988). Vol. 26 (11), pp. 2559-2568

Abstract
This letter represents an initiative started by a number of researchers signed below who are working in the field of numerical modelling of soil mechanics problems. We belive that the type of approach outlined is important in a serious numerical study of all problems in geomechanics and indeed is valid in other areas.
Abstract
This letter represents an initiative started by a number of researchers signed below who are working in the field of numerical modelling of soil mechanics problems. We belive [...]
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Free vibration analysis of plates, bridges and axisymmetric shells using a thick finite strip method
B. Suarez, J. Canet, E. Oñate

Engineering Computations (1988). Vol. 5 (2), pp. 158-164

Abstract
A unified approach for the vibration analysis of curved or straight prismatic plates and bridges and axisymmetric shells using a finite strip method based in Reissner—Mindlin shell theory is presented. Details of obtaining all relevant strip matrices and vectors are given. It is also shown how the use of the simple linear two node strip with reduced integration leads to direct explicit forms of all relevant matrices. Examples of application which show the accuracy of the linear strip for free vibration analysis of structures are presented.
Abstract
A unified approach for the vibration analysis of curved or straight prismatic plates and bridges and axisymmetric shells using a finite strip method based in Reissner—Mindlin [...]
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A constitutive model for cracking of concrete based on the incremental theory of plasticity
E. Oñate, S. Oller, J. Oliver, J. Lubliner

Engineering Computations (1988). Vol. 5 (4), pp. 309-319

Abstract
A constitutive model based on classical plasticity theory for non‐linear analysis of concrete structures using finite elements is presented. The model uses the typical parameters of non‐associated plasticity theory for frictional materials and a modified Mohr‐Coulomb yield surface is suggested. Onset and amount of cracking at a point are controlled by the values of the effective plastic strain and thus it can be studied by a posteriori postprocessing of numerical results. The accuracy and objectivity of the model is checked out with some examples of application.
Abstract
A constitutive model based on classical plasticity theory for non‐linear analysis of concrete structures using finite elements is presented. The model uses the typical parameters [...]
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Nonlinear analysis of reinforced concrete plate and shell structures using 20-noded isoparametric brick elements
M. Cervera, E. Hinton, O. Hassan

Computers and Structures (1987). Vol. 25 (6), pp. 845-869

Abstract
This paper describes an efficient and accurate, 3-D finite element model which may be adopted in the nonlinear analysis of reinforced concerete plate and shell structures. Benchmark tests are undertaken to check the computational model.
Abstract
This paper describes an efficient and accurate, 3-D finite element model which may be adopted in the nonlinear analysis of reinforced concerete plate and shell structures. [...]
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A total Lagrangian formulation for the geometrically nonlinear-analysis of structures using finite-elements. Part II: arches, frames and axisymmetric shells
J. Oliver, E. Oñate

Int. J. Numer. Meth. Engng. (1986). Vol. 23 (2), pp. 253-274

Abstract
A geometrically nonlinear finite element formulation based on a total Lagrangian approach for axisymmetric shells, arches and frames has been presented. The formulation allows for large displacement-large rotations of the structure. Shear deformation effects have also been taken into account. It has been shown how the formulation can be presented in a unified manner to treat simultaneously the three types of structures.
Abstract
A geometrically nonlinear finite element formulation based on a total Lagrangian approach for axisymmetric shells, arches and frames has been presented. The formulation allows [...]
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Preconditioned conjugate gradient method for the non‐linear finite element analysis with particular reference to 3D reinforced concrete structures
M. Cervera, Y. Liu, E. Hinton

Engineering Computations (1986). Vol. 3 (3), pp.235-242

Abstract
A hierarchically preconditioned conjugate gradient (PCG) method for finite element analysis is presented. Its use is demonstrated for the difficult problem of the non‐linear analysis of 3D reinforced concrete structures. Examples highlight the dramatic savings in computer storage and more modest savings in solution times obtained using PCG especially for large problems.
Abstract
A hierarchically preconditioned conjugate gradient (PCG) method for finite element analysis is presented. Its use is demonstrated for the difficult problem of the non‐linear [...]
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Análisis no lineal de tanques criogénicos bajo cargas térmicas
J. Oliver, E. Oñate, J. Peraire, R. Chueca

Hormigón y Acero (1985). Vol. 155, pp. 99-123
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A finite element formulation for the analysis of marine pipelines during laying operations
J. Oliver, E. Oñate

Journal of Pipelines (1985). Vol. 5 (1), pp. 15-35

Abstract
In this paper a finite element formulation for the deformation analysis of submarine pipelines during laying operations is presented. The formation allows for large displacement/rotations and the effect of nonconservative water loads. An iterative procedure to deal with the changing boundary conditions at the seafloor is also presented. Numerical results for two pipeline laying cases, obtained using three noded isoparametrical one-dimensional curved elements, are given.
Abstract
In this paper a finite element formulation for the deformation analysis of submarine pipelines during laying operations is presented. The formation allows for large displacement/rotations [...]
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A total Lagrangian formulation for the geometrically nonlinear analysis of structures using finite elements. Part I. Two‐dimensional problems: Shell and plate structures
J. Oliver, E. Oñate

Int. J. Numer. Meth. Engng. (1984). Vol. 20 (12), pp. 2253-2281

Abstract
A total Lagrangian finite element formulation for the geometrically nonlinear analysis (large displacement/large rotations) of shells is presented. Explicit expressions of all relevant finite element matrices are obtained by means of the definition of a local co‐ordinate system, based on the shell principal curvature directions, for the evaluation of strains and stresses. A series of examples of nonlinear analysis of shell and plate structures is given.
Abstract
A total Lagrangian finite element formulation for the geometrically nonlinear analysis (large displacement/large rotations) of shells is presented. Explicit expressions of [...]
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Estudio de la distribución transitoria del gas en redes urbanas por el método de los elementos finitos
B. Suárez, E. Oñate

Anales de Ingeniería Mecánica (1984). Vol. 2 (1), pp. 59-68

Abstract
Se representa una formulación por elementos finitos que permite simular la distribución transitoria de presiones y caudales del gas en redes urbanas. Esta formulación, que parte de las ecuaciones básicas que proporciona la mecánica de fluidos para la circulación de un gas en régimen variable por conductos cilíndricos, utiliza elementos finitos unidimensionales parabólicos para discretizar los distintos tramos de la red y un esquema paso a paso de integración en el tiempo que supone una variación lineal de la presión del gas en cada intervalo de tiempo. La formulación se aplica al caso real de la red media presión de la ciudad de Barcelona utilizando algunos resultados experimentales para confirmar su eficiencia y aproximación.
Abstract
Se representa una formulación por elementos finitos que permite simular la distribución transitoria de presiones y caudales del gas en redes urbanas. Esta formulación, [...]
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Posibilidades de los ordenadores personales en el cálculo de estructuras por el método de los elementos finitos
E. Oñate, Á. Gaona, J. Oliver, B. Suarez

Revista de Obras Públicas (1983). Vol. 130 (3212), pp. 231-248
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Una formulación para el estudio, por el método de los elementos finitos, de la deformación de tuberías marinas durante su instalación
J. Oliver, E. Oñate

Revista de Obras Públicas (1983). Vol. 130 (3218), pp. 747-763

Abstract
La ejecución de emisarios submarinos para saneamiento y la instalación de tuberías para transporte de productos petrolíferos son ejemplos de la necesidad de conocer los esfuerzos y deformaciones que se producen en el tendido de tuberías submarinas, a cuyo estudio, mediante elementos finitos en diversas condiciones de instalación, se dedica este artículo, que permite la obtención de ábacos de cálculo o formulas sencillas aplicables en los distintos casos.
Abstract
La ejecución de emisarios submarinos para saneamiento y la instalación de tuberías para transporte de productos petrolíferos son ejemplos de la [...]
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A viscous shell formulation for the analysis of thin sheet metal forming
E. Oñate, O. Zienkiewicz

Int. J. Mechanical Sciences (1983). Vol. 25 (5), pp. 305-335

Abstract
A finite element method to analyse large plastic deformations of thin sheets of metal is presented. The formulation is based on an extension of the general viscoplastic flow theory for continuum problems to deal with thin shells. Axisymmetric situations are considered first and here the simple two noded reduced integration element is used. Numerical results for the stretch forming and deep drawing of circular sheets are presented and comparison with experimental results is made. The second part of the paper deals with the deformation of sheets of arbitrary shape. The general viscous shell element is derived from the standard reduced integration, “thick shell element. Numerical results for simple 3-D sheet forming problems are given.
Abstract
A finite element method to analyse large plastic deformations of thin sheets of metal is presented. The formulation is based on an extension of the general viscoplastic flow [...]
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A comparison of the linear, quadratic and cubic mindlin strip elements for the analysis of thick and thin plates
E. Oñate, B. Suarez

Computers and Structures (1983). Vol. 17 (3), pp. 427-439

Abstract
The behaviour of the linear, quadratic and cubic elements of the Mindlin plate strip family for thick and very thin plate analysis is investigated in this paper. Selective integration techniques are used to ensure the good behaviour of the elements when dealing with thin plates. Numerical results showing the convergence and accuracy of the elements for the analysis of plates of a wide range of thicknesses are given. The general performance of the three elements is discussed in detail. In particular, the linear element with a single integration point seems to be the best value strip element for practical purposes.
Abstract
The behaviour of the linear, quadratic and cubic elements of the Mindlin plate strip family for thick and very thin plate analysis is investigated in this paper. Selective [...]
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A unified approach for the analysis of bridges, plates and axisymmetric shells using the linear mindlin strip element
E. Oñate, B. Suarez

Computers and Structures (1983). Vol. 17 (3), pp. 407-426

Abstract
In this paper a finite strip formulation which allows to treat bridges, axisymmetric shells or plate structures of constant transverse cross section in an easily and unified manner is presented. The formulation is based on Mindlin's shell plate theory. One dimensional finite elements are used to discretize the transverse section and Fourier expansions are used to define the longitudinal/circumferential behavior of the structure. The element used is the simple two noded strip element with just one single integrating point. This allows to obtain all the element matrices in an explicit and economical form. Numerical examples for a variety of straight and curve bridges, axisymmetric shells and plate structures which show the efficiency of the formulation and accuracy of the linear strip element are given.
Abstract
In this paper a finite strip formulation which allows to treat bridges, axisymmetric shells or plate structures of constant transverse cross section in an easily and unified [...]
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El laboratorio de ensayo de estructuras en modelo reducido de la Escuela de Ingenieros de Caminos de Barcelona
J. Oliver, B. Suárez, E. Blanco, E. Oñate

Acero y Hormigón (1982). Vol. 145, pp. 65-78
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A general formulation for coupled thermal flow of metals using finite elements
O. Zienkiewicz, E. Oñate, J. Heinrich

Int. J. Numer. Meth. Engng. (1981). Vol. 17 (10), pp. 1497-1514

Abstract
A finite element formulation to deal with the flow of metals coupled with thermal effects in presented. The deformation process of the metal is treated using the visco‐plastic flow approach and the solution technique for the coupled problem implies a simultaneous solution for velocities and temperatures. Some aspects of the numerical solution of the problem are given and in the last part of the paper some examples of steady‐state extrusion and rolling problems showing the applicability of the method are shown.
Abstract
A finite element formulation to deal with the flow of metals coupled with thermal effects in presented. The deformation process of the metal is treated using the visco‐plastic [...]
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La formulación del flujo viscoplástico y sus diversas aplicaciones prácticas por el método de los elementos finitos
E. Oñate

Revista de Obras Públicas (1980). Vol. 127 (3178), pp. 115-129
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Flow of solids during forming and extrusion: Some aspects of numerical solutions
O. Zienkiewicz, P. Jain, E. Oñate

Int. J. Solids and Structures (1978). Vol. 14 (1), pp. 15-38

Abstract
In the extrusion and forming of solids the plastic (or viscoplastic) deformations are so large that the elastic strain is negligible. The problem thus becomes one of incompressible viscous, non-Newtonian flow with prescribed boundary velocities. Various formulations of such problems (analogous to those of incompressible solid mechanics) are possible, and the paper investigates two basic processes. Details of application to some examples of steady state flow in extrusion, drawing and rolling are given and transient free surface solutions are demonstrated for stretch forming and deep drawing. The formulation is shown to be capable of dealing with boundary friction and strain hardening. The coupling with thermal effects is demonstrated in the last section of the paper, and in addition, some practical problems of elastic spring-back which occur on the removal of load are discussed.
Abstract
In the extrusion and forming of solids the plastic (or viscoplastic) deformations are so large that the elastic strain is negligible. The problem thus becomes one of incompressible [...]
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A simple and efficient element for axisymmetric shells
O. Zienkiewicz, J. Bauer, K. Morgan, E. Oñate

International Journal for Numerical Methods in Engineering (1977). Vol. 11 (10), pp. 1545-1558

Abstract
A two noded, straight element which includes shear deformation effects is presented and shown to be extremely efficient in the analysis of axisymmetric shells. A single point of numerical integration is essential for its success when applied to thin shells where the results compare favourably with those achieved with more complex curved elements.
Abstract
A two noded, straight element which includes shear deformation effects is presented and shown to be extremely efficient in the analysis of axisymmetric shells. A single point [...]
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Diseño óptimo de vasijas de presión usando el método de los elementos finitos y un optimizador no lineal
J. Middleton, E. Oñate

ETSIIT (1977). Vol. 11, pp. 309-325

Abstract
Se presenta un esquema de diseño para vasijas de presión metálicas de manera que se minimice la tensión tangencial en la vasija . La geometría final se establece mediante un procedimiento iterativo que optimiza un modelo matemático que expresa la variación de la tensión tangencial en la vasija. Los parámetros del modelo se calculan para cada interacción a partir de los valores de las tensiones tangenciales en la vasija, determinados por el método de los elementos finitos.
Abstract
Se presenta un esquema de diseño para vasijas de presión metálicas de manera que se minimice la tensión tangencial en la vasija . La geometría [...]
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Analysis of bridges by the finite strip method
E. Oñate

Hormigón y Acero (1977). Vol. 124, pp. 53-85

Abstract
Se presenta el análisis general de estructuras formadas por un ensamblaje de placas y vigas y con sección transversal constante, mediante una combinación de elementos finitos transversalmente y series de Fourier en dirección longitudinal. Se ha tenido en cuenta en el análisis el efecto de la deformación transversal debida al esfuerzo cortante, que puede ser importante si los espesores de los componentes que forman la estructura son considerables. Debido a la generalidad del análisis se evita la dificultad de tener que establecer hipótesis simplificadoras para idealizar la estructura, a veces lejos de la realidad, como ocurre en el análisis clásico mediante las teorías de Guyon-Massonet o la de la losa ortótropa. Asimismo permite el estudio de estructuras complejas, como puentes con sección transversal tipo cajón, etc., resultado ser uno de los métodos más versátiles y económicos para el análisis de puentes de los más diversos tipos. Al final del estudio se analizan diversas estructuras tipo puente, comparándose los resultados obtenidos aplicando el método de la banda finita, el método de los elementos finitos y el método del prisma finito.
Abstract
Se presenta el análisis general de estructuras formadas por un ensamblaje de placas y vigas y con sección transversal constante, mediante una combinación [...]
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Aproximación al efecto de la resistividad del hormigón en la corrosión de armaduras embebidas en hormigón
M. Alonso, C. Andrade, J. González

Materiales de Construcción (1987). Vol. 207, pp. 5-12

Abstract
La resistividad del hormigón se ha venido considerando como uno de los factores que afectan a la velocidad de corrosión de las armaduras, aunque, hasta ahora, la única relación encontrada ha sido la establecida entre los potenciales y la resistividad para acero embebido en hormigón contaminado por cloruros. En este trabajo se establecen comparaciones entre velocidad de corrosión de las armaduras, medida a través del método de determinación de la Resistencia de Polarización, y los datos de resistencia eléctrica medidos a través de la compensación de caída óhmica. Los resultados de i^^^^ y R^^^ se han medido en armaduras embebidas en mortero fabricado con tres tipos de cemento a los que se ha sometido a un proceso de carbonatación acelerada. La relación entri i^^^^ y R^^^^ es muy similar en todos los casos y sugiere que la resistencia del hormigón puede actuar como un factor controlante de la velocidad de corrosión de las armaduras.
Abstract
La resistividad del hormigón se ha venido considerando como uno de los factores que afectan a la velocidad de corrosión de las armaduras, aunque, hasta ahora, [...]
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Evaluación de la eficacia de una reparación para hormigón contaminado con cloruros
C. Andrade, B. Bacle, M. Alonso, J. Conde-Salazar

Materiales de Construcción (1988). Vol. 211, pp. 25-40

Abstract
En el presente trabajo se describen los ensayos que se están efectuando en un viaducto de las cercanías de Madrid y que tía sufrido importantes daños por corrosión de armaduras. Estos Ensayos consisten en la medida de los potenciales de corrosión y en un próximo futuro, de la velocidad de corrosión (método de la Resistencia de Polarización Aparente). También se presenta la metodología de los ensayos de laboratorio efectuados para caracterizar la capacidad protectora hacia las armaduras del sistema de reparación utilizado en el viaducto. Los resultado de estos ensayos han mostrado que los materiales de reparación no resultan idóneos para la función repasivante y protectora que deberán desempeñar. Se destaca, finalmente, la necesidad de desarrollar una normativa de ensayos adecuada que permita caracterizar a estos materiales de reparación cuando van a ser usados en obras dañadas por corrosión de armaduras.
Abstract
En el presente trabajo se describen los ensayos que se están efectuando en un viaducto de las cercanías de Madrid y que tía sufrido importantes daños [...]
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Influencia de la conductividad y fuerza iónica de soluciones sintéticas que simulan la fase acuosa del hormigón en el fenómeno de la corrosión de armaduras
S. Goñi, A. Moragues, C. Andrade

Materiales de Construcción (1989). Vol. 215, pp. 19-28

Abstract
Este trabajo presenta el estudio cuantitativo, mediante la técnica de Resistencia de Polarización (Rp), de la influencia de los iones Cí y OH' en la corrosión de armaduras de acero, en un medio acuoso sintético de similar composición al contenido en los poros del hormigón. Fuerza iónica, conductividad (resistividad) y sus variaciones en función de la concentración de dichos iones, han sido los parámetros de interés escogidos para la evaluación del proceso, además de las medidas de intensidad y potenciales de corrosión. Los resultados muestran claramente el antagonismo de los iones Cí y OH', cuyo carácter agresivo o protector disminuye a medida que aumenta la fuerza iónica del medio.
Abstract
Este trabajo presenta el estudio cuantitativo, mediante la técnica de Resistencia de Polarización (Rp), de la influencia de los iones Cí y OH' en [...]
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Propiedades dieléctricas de pastas de cemento con bajo contenido en agua libre
C. Andrade, L. Soler, J. Frutos

Boletin de la Sociedad Española de Cerámica y Vidrio (1995). Vol. 34 (5-6), pp. 414-416

Abstract
El hormigón eléctricamente se comporta como un aislante o como un conductor en función de su contenido de agua. Así, el hormigón saturado de humedad presenta valores de resistividad de 50 W m (a 1 KHz) lo que le sitúa en el rango de los semiconductores. Sin embargo, cunado se seca a 100 ºC, la resistividad alcanza valores del orden de 109 W m (a 1KHz), que corresponde a la de un aislante. Por lo tanto, el contenido en agua de los poros del hormigón tiene un gran efecto en su constante dieléctrica. En el presente trabajo se relaciona la constante dieléctrica de la pasta con su contenido de agua a partir de medidas de Espectroscopia de Impedancia Eléctrica (EIS). Para ello se prepararon probetas con una relación a/c=0, 5 con y sin adición de un 2% de CaCl2 que han sido caracterizadas para diferentes contenidos de humedad. Se presenta la dependencia de la constante dieléctrica de estas muestra con la frecuencia, contenido de agua y de cloruros. Los resultados ponen de manifiesto que la constante dieléctrica aumenta con el contenido de agua, siendo los valores muy dependiente de la frecuencia.
Abstract
El hormigón eléctricamente se comporta como un aislante o como un conductor en función de su contenido de agua. Así, el hormigón saturado [...]
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Influencia de la humedad relativa y la temperatura en las velocidades de corrosión de estructuras de hormigón
C. Andrade, M. Alonso, J. Sarría

Materiales de Construcción (1998). Vol. 251, pp. 5-18

Abstract
Cuando el acero se despasiva, la corrosión se empieza a desarrollar a una velocidad que depende principalmente de la cantidad de humedad contenida en los poros del hormigón. En estructuras expuestas a la atmósfera, este contenido de humedad dependerá, no sólo de la humedad relativa del ambiente, sino también de las variaciones de temperatura que se producen con los ciclos día-noche. Para avanzar en el conocimiento de la influencia de las variables climáticas en la velocidad de corrosión de estructuras reales, se han llevado a cabo diversos experimentos. Primero se han realizado medidas de corrosión de barras de acero sumergidas en soluciones que simulan la solución de los poros del hormigón sometidas a varias temperaturas y se han registrado sus variaciones de contenido en oxígeno, de la relación Cl/OH y de su conductividad. También se han efectuado medidas en probetas de hormigón sometidas a una exposición a la atmósfera no protegidas de la lluvia. Los resultados han permitido deducir que las variaciones de temperatura tienen un efecto múltiple en los diversos parámetros, que se contrapesan unos a otros. Así, el oxígeno y el pH disminuyen al elevarse la temperatura pero la proporción de Cl aumenta. La resistividad es el parámetro que mejor se ajusta a las variaciones de la velocidad de corrosión.
Abstract
Cuando el acero se despasiva, la corrosión se empieza a desarrollar a una velocidad que depende principalmente de la cantidad de humedad contenida en los poros del [...]
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Nuevas técnicas avanzadas para la medida in situ de la corrosión en hormigón armado
C. Andrade, I. Martínez, M. Alonso, J. Fullea

Materiales de Construcción (2001). Vol. 263-264, pp. 97-108

Abstract
Las técnicas de medida de la corrosión en hormigón armado se investigan muy poco en comparación con el creciente número de publicaciones sobre este tema. Sin embargo, existen muchas posibilidades y retos que todavía no han sido exploradas. En el presente artículo se descubren algunas de las presentes posibilidades de las técnicas electroquímicas, tanto in-situ como en laboratorio. En cuanto a las técnicas insitu se refiere, se comentan las posibilidades y limitaciones de los métodos actuales de medida de la Resistencia de Polarización, Rp. Se presta particular atención ante la necesidad de utilizar un anillo de guarda modulado con sensores que controlen esta modulación para obtener valores adecuados de velocidad de corrosión. Después se describen las bases de la nueva técnica relacionada con la medida del estado pasivo en estructuras protegidas catódicamente. También se presentan las bases de un nuevo método de medida de la corrosión sin necesidad de tocar el metal. En cuanto al uso de sensores embebidos, la experiencia, hasta el momento, muestra la difícil interpretación de los datos obtenidos, debido a la importante influencia del efecto de la temperatura. Finalmente, se presentan algunos comentarios sobre la necesidad de trabajar conjuntamente los especialistas en materiales y en estructuras.
Abstract
Las técnicas de medida de la corrosión en hormigón armado se investigan muy poco en comparación con el creciente número de publicaciones [...]
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Late Holocene evolution of the lower Tagus alluvial plain and heavy metals content : preliminary results
C. Ramos, E. Reis, A. Ramos, T. Azevedo, M. Freitas, C. Andrade

Geographical Research Letters (2001). Vol. 27, 163-178

Abstract
This paper aims to contribute to the fluvial dynamic knowledge of the Lower Tagus during the late Holocene. Two cores were done in selected geomorphological positions at the alluvial plain. Each ten centimeters of sediments were submitted to sedimentological and geochemical analyses in order to identify human contamination by heavy metals, sedimentation rates and environmental changes in the main channel position The main conclusions are: (1) The witness of the lateral migration of the fluvial channel; (2) The very irregular sedimentation rate, from 3mm per year to 0.1mm per year; (3) The diversified contamination of fluvial sediments and fluvial channels by heavy metals, namely Cu due to cooper sulphate vineyards and Pb due to petrol and Cr from the tanning industries
Abstract
This paper aims to contribute to the fluvial dynamic knowledge of the Lower Tagus during the late Holocene. Two cores were done in selected geomorphological positions at the [...]
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Determinación del contenido de OH en la fase acuosa de los poros de matrices cementantes por un método empírico de lixiviación
M. Castellote, M. Alonso, C. Andrade

Materiales de Construcción (2002). Vol. 265, pp. 39-56

Abstract
The most reliable method to determine the concentration of hydroxyl ions in the aqueous phase of hardened cementitious materials is the squeezing of concrete at high pressures. However, this method needs special equipment as well as a relatively high amount of sample to be carried out. In present research, the determination of the OH concentration in the concrete pore solution is undertaken by a leaching method in granulated samples. The experimental program has been made using mortars with 5 different binders and three different leaching solutions. In the treatment of the results, different phenomena (dilution + dissolution of solid phases) occurring during leaching have been taken into account until reaching the target values validated by comparison with those obtained by means of the high pressure technique. The agreement found is good enough, for every binder tested, in spite of the fact that fully understanding of the leaching mechanism is not achieved and that concentrations and not activities of the ions are taken into account in the calculations. Therefore, the method suggested is empirical at present stage.
Abstract
The most reliable method to determine the concentration of hydroxyl ions in the aqueous phase of hardened cementitious materials is the squeezing of concrete at high pressures. [...]
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Avances en el modelado de la penetración de cloruros en estructuras de hormigón expuestas al ambiente marino
M. Castellote, C. Andrade, M. Alonso

Cemento y Hormigón (2002). Vol. 834, pp. 40-53

Abstract
El transporte de iones cloruro a través de los poros del hormigón presenta un gran interés en relación con la durabilidad de las estructuras de hormigón armado, ya que éstos iones son los agentes más agresivos para las armaduras. Por ello, en los últimos años y en la actualidad se está llevando a cabo un gran esfuerzo de investigación para modelizar la penetración de cloruros así como el umbral límite que produce la despasivación de las armaduras. Sin embargo, el fenómeno es muy complejo, ya que viene condicionado por la propia estructura de la red porosa del hormigón, por la fuerza iónica de la fase acuosa de los poros, así como por las condiciones medioambientales (macroclima y microclima en las que se sitúa la estructura). La vida útil o tiempo hasta corrosión se estima actualmente a través del cálculo de los coeficientes de difusión en estado estacionario, Ds, y no estacionario, Dns, y posterior resolución de la ley de Fick (medio semi-infinito y concentración exterior constante), que ha demostrado no dar resultados fiables, debido precisamente a que la interacción cloruro/material cementante es mucho más compleja de lo que indica la solución a la ecuación de Fick. Se necesita pues avanzar en el conocimiento y establecer condiciones de contorno más reales, así como desarrollar procedimientos, basados en la medida de diversos parámetros de transporte, para realizar determinaciones tanto en laboratorio como en obra. En este artículo se recogen los métodos más utilizados para la determinación de los coeficientes de difusión, así como los modelos que se preconizan en la literatura.
Abstract
El transporte de iones cloruro a través de los poros del hormigón presenta un gran interés en relación con la durabilidad de las estructuras [...]
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Caracterización de la durabilidad de los hormigones de polvo reactivo (HPR) con fibras metálicas y sin fibras
M. Sanjuán, C. Andrade, M. Cheyrezy

Cemento y Hormigón (2002). Vol. 837, pp. 32-45

Abstract
La utilización de aditivos reductores de agua y la incorporación de partículas ultra finas en los hormigones, han permitido mejorar considerablemente su rendimiento mecánico así como su durabilidad. La reducción de la porosidad se traduce en una gran resistencia de los hormigones frente a la penetración de agentes agresivos. En este trabajo la durabilidad de los Hormigones de Polvo Reactivo (HPR) se compara con la de dos hormigones de referencia H-30 y H-80. El HPR presenta una resistencia muy buena frente a la carbonatación, a la penetración de iones cloruro, a la abrasión y a los ciclos de hielo-deshielo. El estudio de la cinética de la corrosión de las armaduras metálicas en el HPR se ha realizado por vía electroquímica. Las medidas experimentales asociadas a cálculos de predicción permiten establecer las velocidades de penetración de los agresivos estudiados y dimensionar el recubrimiento mínimo de las armaduras pretensadas que se deben utilizar.
Abstract
La utilización de aditivos reductores de agua y la incorporación de partículas ultra finas en los hormigones, han permitido mejorar considerablemente [...]
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Ciencia y tecnología de materiales: de las sombras a las luces.
C. Ruiz, A. Andrés, C. Andrade

Arbor (2002). Vol. 679-680, pp. 605-640

Abstract
En este artículo se analiza la presencia de la mujer en las escalas del Consejo Superior de Investigaciones Científicas (CSIC) centrándonos en el Área de Ciencia y Tecnología de Materiales. Los datos indican que algo se ha hecho mal desde el principio para que un área tan joven presente cifiras tan alarmantes de desigualdad de género, con sólo un 3% de Profesoras de Investigación cuando las mujeres representan el 31% del personal científico del área. Es una realidad la existencia de un techo de cristal que impide que las mujeres alcancen los puestos de máxima responsabilidad. Tanto las mujeres jóvenes como los hombres no son aún muy conscientes de su existencia, no se ve, es transparente, sólo te topas con él cuando tratas de atravesarlo. No se manifiesta de igual manera en todos los Centros, en algunos es más fi^ágil, en otros es cristal blindado.
Abstract
En este artículo se analiza la presencia de la mujer en las escalas del Consejo Superior de Investigaciones Científicas (CSIC) centrándonos en el Área [...]
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Efecto de la distancia al mar en la agresividad por cloruros en estructuras de hormigón en la costa brasileña
C. Andrade, I. Padaratz, C. Alonso, G. Meira

Materiales de Construcción (2003). Vol. 271-272, pp. 179-188

Abstract
La influencia de la distancia al mar es un tema clave en el estudio de la agresividad salina en zona de atmósfera marina, ya que permite conocer cómo afecta a la durabilidad de las construcciones cuando aumenta la distancia al mar. Este trabajo presenta resultados de un estudio experimental que valora la situación a través de la medida del depósito de cloruros de la niebla salina y en probetas de hormigón expuestas a distintas distancias desde el mar en la ciudad de Joâo Pessoa, ubicada en la costa noreste de Brasil. Los resultados indican una importante disminución del depósito de cloruros de la niebla salina a medida que se aumenta la distancia al mar, especialmente en los primeros doscientos metros. La concentración de cloruros en el hormigón indica un comportamiento semejante. Sin embargo, la disminución de la concentración de cloruros con la distancia ocurre de forma más suave que en la niebla. A pesar de la necesidad de más investigación, aspectos como la relación entre los cloruros de la niebla y los que se fijan en la superficie del hormigón, los fenómenos que ocurren en el transporte de los cloruros en el hormigón, el efecto del lavado superficial y el efecto piel del hormigón pueden justificar esas diferencias
Abstract
La influencia de la distancia al mar es un tema clave en el estudio de la agresividad salina en zona de atmósfera marina, ya que permite conocer cómo afecta [...]
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Influencia del electrolito externo en el flujo electroosmótico inducido por realcalinización
M. Castellote, C. Andrade, I. Llorente

Materiales de Construcción (2003). Vol. 271-272, pp. 101-111

Abstract
Los métodos electroquímicos de reparación de estructuras dañadas por corrosión de armaduras se basan en la aplicación de corriente continua entre la armadura y un electrodo auxiliar colocado sobre la superficie del hormigón. En el caso de la realcalinización, el objetivo del tratamiento consiste en restaurar la alcalinidad del hormigón alrededor de la armadura, con lo que se consigue la repasivación de la misma. Esta alcalinización se alcanza por la generación de OH- en la hidrólisis del agua que tiene lugar en el acero que actúa como cátodo, aunque también se postula la penetración de carbonatos presentes en el electrolito externo por el establecimiento de un flujo electroosmótico durante el tratamiento, lo que fue demostrado y cuantificado recientemente por los autores, para hormigón carbonatado. En este artículo, se presentan ensayos realizados con el objetivo de estudiar la influencia del electrolito externo en el flujo electroosmótico. Los experimentos se han llevado a cabo sobre mortero portland normalizado, previamente carbonatado, con 4 disoluciones diferentes de Na2CO3 de concentraciones comprendidas en el rango entre 0,1 a 2M. Los resultados indican que el flujo electroosmótico establecido no es constante durante los experimentos, siendo el pH del electrolito el parámetro que determina el potencial zeta y, consecuentemente, el flujo electroosmótico alcanzándose el máximo, en los experimentos realizados en esta investigación, al pH de la disolución reguladora carbonato/bicarbonato
Abstract
Los métodos electroquímicos de reparación de estructuras dañadas por corrosión de armaduras se basan en la aplicación de corriente [...]
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Efecto de la aplicación de campos eléctricos sobre las interacciones entre los iones cloruro y la matriz de cemento
M. Castellote, C. Andrade, C. Alonso

Boletin de la Sociedad Española de Cerámica y Vidrio (2004). Vol. 43 (2), pp. 565-568

Abstract
La determinación de coeficientes de difusión de los iones cloruro a través del hormigón precisa en muchas ocasiones de la aplicación de campos eléctricos con el fin de obtener resultados en plazos razonables de tiempo. Sin embargo, esta aceleración del transporte podría modificar las complejas interacciones que tienen lugar entre los iones cloruro y la matriz de cemento, haciendo que los coeficientes obtenidos mediante ensayos de migración no fueran representativos de condiciones de difusión natural. Este aspecto se aborda en el presente trabajo mediante la realización de ensayos de migración de cloruros en estado estacionario y no estacionario, así como de difusión natural de cloruros y oxígeno en estado estacionario. Como resultado, se ha podido establecer que cuando el transporte se produce por migración, hasta un campo aplicado de 10.5 V/cm, ésta tiene lugar a través de poros del mismo tamaño que por los que se lleva a cabo la difusión natural, produciéndose una interacción más débil del adsorbato con el sustrato que en difusión natural, lo que debe tenerse en cuenta a la hora de diseñar los ensayos de migración para la determinación de los coeficientes de difusión de cloruros en estado no estacionario.
Abstract
La determinación de coeficientes de difusión de los iones cloruro a través del hormigón precisa en muchas ocasiones de la aplicación de [...]
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Opinión de la Secretaria de Estado de Universidades e Investigación
C. Andrade

Revista de Obras Públicas (2005). Vol. 3457, pp. 61-62

Abstract
La puesta en marcha de Plataforma Tecnológica es un hecho que supone una iniciativa novedosa dentro del programa móvil para incentivar la investigación industrial. Los funcionarios de la DG - Investigación han sido siempre entusiastas, promotores de la participación de la empresa en la investigación. La Secretaria de Estado de Universidades e Investigación ha acogido la idea con interés y pretende explorar todas sus posibilidades, por lo que respalda la creación de esta Plataforma nacional de Construcción y nombra un delegado suyo para un seguimiento de su desarrollo.
Abstract
La puesta en marcha de Plataforma Tecnológica es un hecho que supone una iniciativa novedosa dentro del programa móvil para incentivar la investigación [...]
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Influencia del contenido de agua en los conglomerantes fabricados con cemento portland sobre la difusividad del ión cloruro
M. Climent, C. Andrade, J. López, G. Vera, E. Viqueira

Cemento y Hormigón (2005). Vol. 879, pp. 18-34

Abstract
En el presente trabajo se propone un método para la determinación del coeficiente de difusión del ión cloruro a través de probetas de hormigón parcialmente saturadas, con contenidos de agua controlados y bien caracterizados. El procedimiento experimental permite depositar una cantidad inicial limitada de cloruro sobre la superficie de hormigón en estudio. Dicho procedimiento está basado en la interacción de la superficie de hormigón con los productos de combustión del PVC, que contienen fundamentalmente cloruro de hidrógeno gaseoso. Tras devolver las probetas de hormigón a sus cámaras de humedad relativa controlada, se puede estudiar la cinética del transporte de cloruro desde la superficie hacia el interior del hormigón. Los perfiles experimentales de concentración de cloruro, obtenidos a intervalos de tiempo seleccionados, han sido ajustados a un modelo matemático difusional de ¿fuente plana instantánea¿, que se corresponde con las condiciones iniciales y de contorno del procedimiento experimental, y permite obtener los coeficientes de difusión del cloruro.
Abstract
En el presente trabajo se propone un método para la determinación del coeficiente de difusión del ión cloruro a través de probetas de hormigón [...]
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Comportamiento frente a lixiviación de materiales de base cemento
M. Cruz, C. Andrade, A. Hidalgo, E. Guede, M. Sanjuán

Cemento y Hormigón (2006). Vol. 894, pp. 14-25

Abstract
Cuando los materiales de la construcción son aplicados en el exterior, el agua de lluvia, el agua superficial o las aguas subterráneas, pueden ser responsables de que ocurran procesos de lixiviación o procesos de disolución y transporte de componentes de la fase sólida a una fase acuosa. En su interacción con las aguas, los materiales sufren una serie de transformaciones físicas y químicas; el ataque que se produce depende mucho del régimen hidrodinámico, del tipo de cemento y de la dosificación del hormigón. En el presente trabajo se comunican los resultados de varias investigaciones realizadas con financiación de la UE y de Enresa en el que se estudia el comportamiento frente a la lixiviación. Estos trabajos se han ampliado con financiación de Oficemen, para el estudio del comportamiento frente a la lixiviación de metales pesados y otros elementos, en cementos fabricados con combustibles tradicionales y cementos fabricados con combustibles alternativos.
Abstract
Cuando los materiales de la construcción son aplicados en el exterior, el agua de lluvia, el agua superficial o las aguas subterráneas, pueden ser responsables [...]
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Influencia del uso de material fotocatalítico como adición al cemento en la durabilidad de las armaduras embebidas en hormigón
M. Castellote, S. Botija, C. Andrade

Cemento y Hormigón (2006). Vol. 896, pp. 22-27

Abstract
Uno de los aspectos clave de la Innovación en Construcción es el desarrollo de materiales inteligentes. Entre estos materiales se encuentran aquellos que contribuyen a luchar contra la contaminación atmosférica por la inclusión en su composición de agentes fotocatalíticos, como dióxido de titanio, capaces de oxidar contaminantes orgánicos e inorgánicos en presencia de luz ultra violeta. En este trabajo se ha estudiado la influencia del uso de material fotocatalítico como adición al cemento sobre la corrosión de las armaduras embebidas en hormigón, ya que por un lado, la formación de CO2 por la oxidación de moléculas orgánicas en su superficie podría llevar a la aceleración de la carbonatación de la matriz, y por otra parte, la oxidación de iones cloruro a cloro gaseoso evitaría la corrosión por picaduras inducida por aquellos. En este trabajo se presentan los resultados preliminares obtenidos con probetas armadas de mortero de cemento blanco con y sin TiO2 sometidas a distintos ambientes.
Abstract
Uno de los aspectos clave de la Innovación en Construcción es el desarrollo de materiales inteligentes. Entre estos materiales se encuentran aquellos que contribuyen [...]
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Nanociencias del cemento
C. Andrade, M. Castellote

Cemento y Hormigón (2007). Vol. 898, pp. 12-16

Abstract
Con la ayuda de las técnicas de caracterización desarrolladas en las últimas décadas se pudo avanzar en el conocimiento de la microstructura de los materiales y su relación con el comportamiento estructural. Ahora es el turno de profundizar a nivel de la nanoestructura ya que empiezan a existir técnicas capaces de dar información con esa resolución. Se trataría de sentar las bases de las Nanociencias que dan información a nivel atómico. Las Nanotecnologías son entendidas como la capacidad de manipulación de entes del tamaño de nm. En el caso del cemento parece más accesible en el momento actual hablar de nanociencias que de nanotecnologías. Para desarrollar las bases de las Nanociencias del Cemento se ha constituido a nivel europeo la Red Nanocem que integra a unos 120 investigadores permanentes que dirigen en la actualidad unas 60 Tesis Doctorales en universidades y centros de investigación europeos. Los objetivos que se plantea NANOCEM son: a) Identificar, estudiar y elucidar los mecanismos fundamentales que subyacen en problemas específicos de la industria de la Construcción, b) Generar el conocimiento básico requerido para desarrollar nuevos materiales en base cemento y mejorar los existentes y la tecnología implícita en los procesos. c) Mejorar la sostenibilidad de los procesos relacionados con el cemento y el hormigón, d) Promover avances de alta tecnología en los materiales en base cemento y buscar sus aplicaciones y e) Formar graduados universitarios y facilitar su incorporación a la industria del cemento y del hormigón. Los resultados a largo plazo de NANOCEM se espera que sitúen a sus miembros en la vanguardia mundial de la investigación, y a la industria europea le aporten una más elevada eficiencia en sus procesos con el desarrollo de nuevos materiales y aplicaciones más compatibles con el Medio Ambiente. En la actualidad se están financiando 3 proyectos con temas avanzados que se describirán brevemente en el trabajo. También se mencionan los miembros actuales y los proyectos aportados por ellos.
Abstract
Con la ayuda de las técnicas de caracterización desarrolladas en las últimas décadas se pudo avanzar en el conocimiento de la microstructura de [...]
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Lixivación acelerada de materiales en base cemento por aplicación de campos eléctricos
M. Castellote, I. Llorente, C. Andrade, M. Cruz

Cemento y Hormigón (2007). Vol. 903, pp. 16-21

Abstract
Los materiales de base cemento están siendo utilizados cada vez más como matrices confinantes en la inertización de residuos, tanto peligrosos como radiactivos. En su utilización en este ámbito, uno de los principales problemas es el de la degradación a largo plazo, cuya caracterización mediante técnicas tradicionales se hace inviable, por lo que se hace necesario el desarrollo de métodos acelerados, como el basado en la aplicación de campos eléctricos. En este artículo, se presenta un resumen de algunos de los trabajos de los autores en este campo: Monitorización in-situ del tratamiento eléctrico por difracción de neutrones; cuantificación de las fases cristalinas antes y después de un tratamiento acelerado mediante análisis Rietveld de los espectros de difracción de Rayos X con radiación Sincrotrón y por último comparación de los resultados obtenidos por el método acelerado, mediante integración de los perfiles absolutos obtenidos por EDX, con un método estandarizado de lixiviación.
Abstract
Los materiales de base cemento están siendo utilizados cada vez más como matrices confinantes en la inertización de residuos, tanto peligrosos como radiactivos. [...]
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Difusión de cloruros en hormigones expuestos a ambientes marinos. Estudio de 15 años de exposición
C. Andrade, M. Castellote, R. D'Andrea, J. Picón, M. Sanjuán

Cemento y Hormigón (2009). Vol. 935, pp. 22-31

Abstract
El hormigón armado situado en ambientes marinos puede sufrir la corrosión del acero embebido debido a la penetración de los cloruros. Los fenómenos de transporte de los cloruros en el hormigón son complejos y aunque son controlados principalmente por el mecanismo de difusión, los perfiles de concentración de cloruros no siguen fielmente la segunda ley de Fick. Por lo tanto, resulta de vital importancia para conocer la cinética del fenómeno acceder a datos de penetración de los cloruros a largo plazo. En el presente trabajo se comentan los perfiles de concentración de iones cloruro obtenidos en bloques de hormigón de 50x50x200 cm que se han conservado semienterrados en una playa de Huelva cedida al Instituto Eduardo Torroja por la Autoridad Portuaria de Huelva para realizar los ensayos. Los bloques fueron fabricados en 1988 con dos cementos portland, uno de ellos con un bajo contenido de C3A. Se comentan los perfiles de cloruros obtenidos así como la variación del coeficiente de difusión y de la concentración superficial a lo largo del tiempo
Abstract
El hormigón armado situado en ambientes marinos puede sufrir la corrosión del acero embebido debido a la penetración de los cloruros. Los fenómenos [...]
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Análisis no destructivo del estado de degradación en morteros bajo la acción de ciclos hielo-deshielo
E. Menéndez, J. Frutos, C. Andrade

Boletín de la Sociedad Española de Cerámica y Vidrio (2009). Vol. 48 (5), pp. 223-230

Abstract
En el presente trabajo se evalúan diferentes morteros, con distinto grado de daño por la acción de ciclos de hielo-deshielo, analizando su estado mediante diferentes métodos de evaluación habituales. Los resultados obtenidos por estos métodos se comparan con un análisis mediante la técnica de espectroscopía de impedancia, analizándose la capacidad de esta técnica para evaluar el estado de los morteros y el grado de daño interno producido.
Abstract
En el presente trabajo se evalúan diferentes morteros, con distinto grado de daño por la acción de ciclos de hielo-deshielo, analizando su estado mediante [...]
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Evaluación y monitorización de la durabilidad de las cubiertas del Hipódromo de la Zarzuela de Madrid
A. Castillo, C. Andrade, L. Fernández, J. Junquera, G. Ayuso

Informes de la Construcción (2011). Vol. 63 (524), pp. 33-41

Abstract
En el presente trabajo se describen algunos aspectos que se han tenido en cuenta en la restauración que se ha llevado a cabo recientemente en la emblemática obra de Torroja del Hipódromo de La Zarzuela,. Aunque la estructura presenta un muy buen comportamiento, se han producido algunos deterioros locales debido a la corrosión de la armadura por rotura de la impermeabilización y la carbonatacion del hormigón. Lo primero que se realizó fue una evaluación del grado de la corrosión, para posteriormente acometer el proyecto de reparación, que consistió en la inyección de grietas y en el parcheo de zonas deterioradas. Durante la reparación se procedió a la instalación de un sistema de registro de corrosión con sensores permanentes. Se presentan los resultados de la aplicación de técnicas electroquímicas no destructivas utilizadas en la evaluación de estructuras, y se describen el sistema de sensores instalados y sus primeros resultados
Abstract
En el presente trabajo se describen algunos aspectos que se han tenido en cuenta en la restauración que se ha llevado a cabo recientemente en la emblemática [...]
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Evaluación de la corrosión en estructuras de contención nuclear mediante el uso de técnicas electroquímicas no destructivas
I. Martínez, A. Castillo, C. Andrade

Informes de la Construcción (2012). Vol. 64 (528), pp. 519-528

Abstract
Son muchos los planteamientos que se realizan en relación al estado de estas estructuras nucleares y a la posibilidad de prorrogar su vida útil, siendo la corrosión uno de los problemas que más preocupa en la actualidad. Por ello, la evaluación y control de la corrosión en estructuras como los liners de los edificios de contención es extremadamente importante para que éste no sea el motivo que limite la vida de estas estructuras. En el presente trabajo se muestran resultados de la aplicación de técnicas electroquímicas no destructivas en estructuras reales de contención nuclear para la evaluación de la corrosión de armaduras o elementos metálicos embebidos en el hormigón, como son los liners antes mencionados.
Abstract
Son muchos los planteamientos que se realizan en relación al estado de estas estructuras nucleares y a la posibilidad de prorrogar su vida útil, siendo la corrosión [...]
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Diez años de estudio del comportamiento higrotérmico de la cubierta del Museo del Prado
J. Sánchez-Montero, C. Andrade, J. Fullea, P. Linares, G. Sotorrío, F. Barroso, G. Rentero

Informes de la Construcción (2014). Vol. 66 (535), e027

Abstract
In the current paper we present the results of the monitoring of the hygrothermal behaviour during the last ten years of the El Prado Museum roof. Sensors were installed in the south roof of the museum after it underwent mayor repair following a leak over a very important exhibition hall (the one holding Velazquez’s Las Meninas painting). The liquid water sensors reveal that water is retained at the waterproofing layer. These sensors do not show water presence in lower layers of the roof. The humidity sensors show condensation when the ambient temperature drops. The temperature sensors show the insulating capacity of the different layers of the roof, which effectively attenuate the outside temperature changes. The strain sensors placed on the liquid waterproofing layer show a constant increase of strain with time. In summary, the repaired roof can be considered to perform as intended and no more leaks have been detected
Abstract
In the current paper we present the results of the monitoring of the hygrothermal behaviour during the last ten years of the El Prado Museum roof. Sensors were installed in [...]
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Cálculo de la velocidad de propagación de la fisura debido a fragilización por hidrógeno
J. Sánchez, Á. Ridruejo, E. Muñoz, C. Andrade, J. Fullea, P. Andrés

Hormigón y Acero (2016). Vol. 67 (280), pp. 325-332

Abstract
The durability of high strength steels in aggressive media is determined by the presence of hydrogen, in particular hydrogen embrittlement processes. Hydrogen embrittlement is present in many of the failures of structures made with steel components. The effect of interstitial hydrogen within the network of iron has been investigated in previous studies at the atomic level. It is concluded that the main role of hydrogen is not to establish chemical bonds with iron atoms, but to introduce internal stresses that weaken the interactions between iron atoms and decrease fracture toughness. In this work, the spread of a crack has been stimulated inside a matrix of iron in the presence of hydrogen. Hydrogen transport, stress distributions, and the evolution of fracture toughness were analysed together in a multi-physics finite element model. The behaviour in the fracture was simulated using two different models for the cohesive law, one lineal and the other polynomial. Results show that the choice for the cohesive law influences the crack propagation rate and the hydrogen concentration profiles.
Abstract
The durability of high strength steels in aggressive media is determined by the presence of hydrogen, in particular hydrogen embrittlement processes. Hydrogen embrittlement [...]
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Some historical notes on the research in corrosion of reinforcement
C. Andrade

Hormigón y Acero (2018). Vol. 69 (S1), pp. 21-28

Abstract
A brief exercise is made on reporting some achievements in the history of reinforcement corrosion. It is a difficult task to try to summarize because there are numerous protagonists in the history then choices were made from a personal point of view. In the decade 1960–1970, reinforcement corrosion was a subject only of marginal interest because the number of built environment was limited. The use of electrochemical techniques was a milestone which enabled from the decade of the 1970 to study the effect of each variable with much more rigor. The studies on service life started in the decade of 1980, although they were not of general interest until next decade. From 1990 Rilem Committees and the Iberoamerican Program on Corrosion of CYTED extended the knowledge so widely that in the XXI century the subject attracts much research interest.
Abstract
A brief exercise is made on reporting some achievements in the history of reinforcement corrosion. It is a difficult task to try to summarize because there are numerous protagonists [...]
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Test methods for on-site corrosion rate measurement of steel reinforcement in concrete by means of the polarization resistance method
C. Andrade, C. Alonso

Materials and Structures (2004). Vol. 37, pp. 623-643

Abstract
This recommendation covers the description of non-destructive electrochemical test methods for the estimation in large size concrete structures of the instantaneous corrosion current densiti, icor, expressed in gA/cm2, by means of the so called Polarization Resistance technique, Rp, in order to asses the condition of embedded Steel reinforcement related to its corrosion. The values of icor, can be used to assess the rate of degradation of concrete structures affected by reinforcement corrosión. However, the cannot give information on the actual loss in steel cross section which, at present, only can be assessed by means of direct visual observation. Values of the free corrosión potential or half-cell potential, Ecorr [V], of the embedded reinforcing Steel and of the electrical concrete resistance, Re [f)], are obtained as preliminary steps of the Rp measurements. Values of the concrete resistivity, P [~m], can be calculated from Re values providing the geometrical arrangement of the electrodes enables this calculation. Both parameters, Ecorr and Re (or P) may be used to complement the reliability of the ico~r measurements.
Abstract
This recommendation covers the description of non-destructive electrochemical test methods for the estimation in large size concrete structures of the instantaneous [...]
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Revisión sobre el comportamiento de las armaduras galvanizadas en el hormigón
J. González, R. Vargas, C. Andrade

Hormigón y Acero (1977). Vol. 28 (124), pp. 113-131

Abstract
Esta comunicación pretende ofrecer una panorámica de las ventajas e inconvenientes derivados del empleo de las armaduras de acero galvanizados en el hormigón. Se resumen las causas que pueden provocar la corrosión de las armaduras embebidas en el hormigón y se analiza la protección suplementaria que el galvanizado puede conferir a dichas armaduras en condiciones especialmente agresivas. Se mencionan los datos publicados sobre los límites tolerables de cloruros para las armaduras normales, punto en el que se echa en falta la existencia de datos cuantitativos similares para las armaduras galvanizadas y se examina, asimismo, las repercusiones sobre ellas de la carbonatación del hormigón y de la presencia de pilas de aireación diferencial, así como la influencia sobre la adherencia hormigón-armaduras, y el peligro de fragilización de estas, por el hidrógeno desprendido en el curso del fraguado. Finalmente se nombran algunas de las obras donde se han empleado armaduras galvanizadas.
Abstract
Esta comunicación pretende ofrecer una panorámica de las ventajas e inconvenientes derivados del empleo de las armaduras de acero galvanizados en el hormigón. Se [...]
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Electrochemical Behavior of Galvanized Steel in a Calcium Hydroxide-Saturated Solution. A Quantitative Assessment of Corrosion Rate.
C. Andrade, A. Vazquez, J. González

Revista de Metalurgia (1978). Vol. 13, pp. 142-145

Abstract
An electrochemical study has been carried out involving immersion of galvanized steel in a Ca(OH)//2-saturated solution with and without chloride additions. Results show that galvanized steel corrodes steadily during the first few days; after approximately a week, however, it becomes passive, the passivity being perfectly stable both in the presence and absence of chlorides for the entire test period which lasted for more than 60 days' exposure.
Abstract
An electrochemical study has been carried out involving immersion of galvanized steel in a Ca(OH)//2-saturated solution with and without chloride additions. Results show that [...]
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Quantitative measurements of corrosion rate of reinforcing steels embedded in concrete using polarization resistance measurement
C. Andrade, J. González

Materials and Corrosion (1978). Vol. 29 (8), pp. 515-519

Abstract
Up to this time all the methods to measure the corrosion rate of reinforcing steels embedded in hardened concrete have been of the destructive type, which requires much time and materials and makes the full scale study of the phenomenon difficult. The authors have applied the polarization resistance method to bars embedded in hardened mortar and immersed in Ca(OH)2‐saturated solution, and have found an acceptable agreement between the gravimetric and the electrochemical weight loss data.
Abstract
Up to this time all the methods to measure the corrosion rate of reinforcing steels embedded in hardened concrete have been of the destructive type, which requires much time [...]
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Valores del potencial de corrosión y de a resistencia de polarización de armaduras galvanizadas embebidas en hormigón
C. Andrade, J. González

Materiales de Construcción (1978). Vol. 28 (172), pp. 71-80

Abstract
Muchas de las estructuras de hormigón armado se muestran exentas de corrosión aun después de periodos muy prolongados de servicio. Ello es debido a que en el hormigón el electrolito está constituido por la fase líquida que rellena sus poros y que es, fundamentalmente, una disolución saturada de CA(OH)2, con un pH alrededor de 13. A este elevado pH y a los potenciales de corrosión Ecorr, que presentan las armaduras, el acero se encuentra en la zona de pasividad descrita por Pourbaix, permaneciendo protegido indefinidamente mientras no cambien las condiciones del medio. Este cambio en las condiciones de servicio del hormigón capaz de introducir en la zona de corrosión al acero de las armaduras, se puede producir con relativa frecuencia. Así, la carbonatación del cemento disminuye el pH del hormigón y provoca una corrosión generalizada, la presencia de iones despasivantes o de fisura conduce a corrosión localizada y, finalmente, la acción simultánea de tensiones mecánicas y factores agresivos puede ser la causa de corrosión bajo tensiones. Así pues, es aconsejable recurrir a una protección suplementaria de los aceros cuando se prevean situaciones que puedas provocar la corrosión de las armaduras. Entre los varios métodos de protección que se utilizan se viene ensayando desde hace varios lustros, con resultados muy contradictorios, la galvanización en caliente de los redondos.
Abstract
Muchas de las estructuras de hormigón armado se muestran exentas de corrosión aun después de periodos muy prolongados de servicio. Ello es debido [...]
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Corrosion of Reinforcing Bars in Carbonated Concrete
J. González, J. Algaba, C. Andrade

British Corrosion Journal (1980). Vol. 15 (3), pp. 135-139

Abstract
In all published studies of cement carbonation there has been general agreement that it must be considered as a cause of generalised corrosion in reinforcements, but quantitative data have been provided in very few cases. In the present work the intensity of attack has been modified by means of the accelerated carbonation of mortar specimens without additives, with 2% CaCl2, and with 3% NaNO2 It has been shown that a critical level of atmospheric moisture must also be present for considerable attack to occur. The measurement of polarisation resistance (Rp) has been used to evaluate the intensity of corrosion of the reinforcements. This method has already been usefully applied by the authors to investigations of corrosion of steel bars in hardened concrete specimens.
Abstract
In all published studies of cement carbonation there has been general agreement that it must be considered as a cause of generalised corrosion in reinforcements, but quantitative [...]
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Influencia de la dosificación en cemento sobre la corrosión de armaduras, negras y galvanizadas provocado por lo penetración de Cl- en el mortero
C. Andrade, G. Jauregui, J. González

Materiales de Construcción (1981). Vol. 31 (183), pp. 45-52

Abstract
En el presente trabajo se aborda el estudio de la corrosión de armaduras, tanto desnudas como galvanizadas, producida por la penetración de agua de mar en nueve calidades (dosificaciones y por lo tanto porosidades) diferentes de mortero de cemento portland en el que se embebieron redondos a tres profundidades (0,5-1,5-2,5 cm). Las probeta de 7 X 7 X 7 cm se conservaron sumergidas durante 1 año. Para la evaluación de la velocidad de corrosión se ha utilizado la Resistencia de Polarización, técnica que permite el seguimiento continuo de la despasivación progresiva que provocan los Cl- al llegar a la armadura. Se aportan resultados sobre la penetración de Cl-, discutiéndose las relaciones encontradas entre: corrosión, % de Cl-, porosidad y dosificación de cemento. Finalmente se compara el comportamiento frente a la corrosión de las armaduras de acero desnudo respecto de las galvanizadas.
Abstract
En el presente trabajo se aborda el estudio de la corrosión de armaduras, tanto desnudas como galvanizadas, producida por la penetración de agua de mar en nueve [...]
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Effect of Carbonation, Chlorides and Relative Ambient Humidity on the Corrosion of Galvanized Rebars Embedded in Concrete
J. Gozález, C. Andrade

British Corrosion Journal (1982). Vol. 17 (1), pp. 21-28

Abstract
The variation with time of the corrosion rates of galvanized steel and bare steel rebars has been studied as a function of the relative ambient humidity, mortar carbonation and the presence or absence of chloride ions. Corrosion rates are estimated from Rp measurements with electronic compensation for the ohmic drop between the working imd reference electrodes. It is shown that a normal galvanized coating with a continuous layer of practically pure zinc in contact with mortar gives effective protection to the steel reinforcing bars against the aggressive action of carbonation and chlorides. The protective effect of this galvanized coating is much greater under partial immersion conditions of the mortar than in very humid atmospheres, although in the latter case the corrosion rate decreases with time
Abstract
The variation with time of the corrosion rates of galvanized steel and bare steel rebars has been studied as a function of the relative ambient humidity, mortar carbonation [...]
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Techniques electrochimiques qualitatives et quantitatives pour mesurer les effets des additions sur la corrosion des armatures
C. Andrade, J. González

Silicates Industriels (1982). Vol. 47, pp. 289-295

Abstract
Les auteurs resument une serie de considerations theoriques sur l'incidence que les additions actives peuvent avoir dans la corrosion des armatures. Ensuite, ils attirent l'attention sur le manque de normes ou recommandations de travail, qui s'appuient sur des essais suffisants, et qui pourraient permettre de delimiter les causes et conditions qui influent sur la duree des armatures ; finalement ils exposent une systematique d'essais qu'ils ont realisee pour etudier cette incidence au moyen de techniques electrochimiques, et les differences de comportement trouvees entre les differents ciments.
Abstract
Les auteurs resument une serie de considerations theoriques sur l'incidence que les additions actives peuvent avoir dans la corrosion des armatures. Ensuite, ils attirent [...]
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Les effets des cycles d’humidité sur la corrosion des armatures galvanisées dans les mortiers carbonatés et non carbonatés
J. González, A. Vazquez, C. Andrade

Matériaux et Construction (1982). Vol. 15, pp. 271-278

Abstract
Galvanisation of steel reinforcement has been usual practice for the last decades as a protection against certain types of aggressive agents. However, recent results, mostly European, have thrown doubts on the usefulness of galvanisation. The results presented here contribute to explain this controversy. We have identified three factors that may influence the corrosion kinetics of galvanized steel bars embedded in concrete, although they usually go unheeded: type of galvanized coating, type of cement and humidity during curing and hardening. From these factors, this report deals mostly with ambient humidity. Corrosion rate was basically estimated from the Polarisation Resistance in reinforced mortar specimens that were cyclically subjected during curing and hardening to different ambient humidities. The influence on the corrosion kinetics of the structure of the galvanized coating which, in turn, depends on the chemical composition of the steel, is also discussed. Finally, the behaviour of bare and galvanized steel are compared, and criteria are given on the usefulness of galvanized coatings.
Abstract
Galvanisation of steel reinforcement has been usual practice for the last decades as a protection against certain types of aggressive agents. However, recent results, mostly [...]
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Corrosion Rate of Galvanized Steel Immersed in Saturated Solutions of Ca(OH)2 in the pH Range 12–13 8
A. Macías, C. Andrade

British Corrosion Journal (1983). Vol. 18 (2), pp. 82-87

Abstract
The influence of the alkaline content of cement on the corrosion kinetics of galvanized reinforcements has been studied, by means of the polarisation resistance method, in saturated solutions of Ca(OH)2 with additions of NaOH, KOH and SO2 4, thus simulating the liquid phase of concrete.It has been established that below a threshold pH the coating protects the surface; above this pH the coating is attacked, disappearing in a few days. Cements with low alkali contents and proper concrete dosage must therefore be used to ensure that the pH remains below the threshold value.
Abstract
The influence of the alkaline content of cement on the corrosion kinetics of galvanized reinforcements has been studied, by means of the polarisation resistance method, in [...]
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Corrosion rate of galvanized steel immersed in saturated solutions of Ca(OH)2 in the pH Range 12-13.8
A. Macías, C. Andrade

British Corrosion Journal (1983). Vol. 18 (2), pp. 82-87

Abstract
The influence of the alkaline content of cement on the corrosion kinetics of galvanized reinforcements has been studied, by means of the polarisation resistance method, in saturated solutions of Ca(OH)2 with additions of NaOH, KOH and SO²4, thus simulating the liquid phase of concrete. It has been established that below a threshold pH the coating protects the surface; above this pH the coating is attacked, disappearing in a few days. Cements with low alkali contents and proper concrete dosage must therefore be used to ensure that the pH remains below the threshold value.
Abstract
The influence of the alkaline content of cement on the corrosion kinetics of galvanized reinforcements has been studied, by means of the polarisation resistance method, in [...]
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SEM Study of the Corrosion Products of Galvanized Reinforcements Immersed in Solutions in the pH Range 12·6 to 13·6
M. Blanco-Varela, C. Andrade, A. Macías

British Corrosion Journal (1984). Vol. 19 (1), pp. 41-48

Abstract
In previous work on galvanized reinforcements in contact with Ca-containing highly alkaline media the authors have reported the existence of a threshold pH below which the Zn in contact with such a medium is passivated, but at pH values above this it corrodes continuously until it totally disappears. In this paper, after a brief literature review concerning the identification of the corrosion products in these media, they report that the passivation detectedfrom the data of the polarisation technique agreed with the results of an SEM study. This showed that below the threshold pH value the surface is covered with a continuous layer of calcium hydr.oxyzinccite, Ca (Zn(OH)3)2.2H2O, and above this pH this layer is increasingly composed ofnon-passivating ZnO, to the detriment of the calcium hydroxyzincate content. They have also established that it is the (Ca2+) ions that control the amount of calcium hydroxyzincate formed, and therefore the likelihood of the formation of a continuous passivating layer. Finally, they report that if the calcium hydroxyzincate isperfectly developed, a later increase of thepH does not affect the stability.
Abstract
In previous work on galvanized reinforcements in contact with Ca-containing highly alkaline media the authors have reported the existence of a threshold pH below which the [...]
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Corrosion rate of three different types of galvanized coatings of steel reinforcements in contact with mortar
A. Molina, M. Blanco, C. Andrade

International Congress on Metallic Corrosion (1984). Vol. 1, pp. 412-417

Abstract
Corrosion of galvanized reinforcements in concrete is controlled by three factors: the type of the cement, the type of metallographic structure and the humidity of conservation of the concrete. The behaviour of three different types of galvanized coating embedded in mortars made with three different Portland cements: low, medium and high alkali content, was studied. The corrosion rate was measured by means of the linear polarization (Polarization Resistance) technique. The results show that the thicker the pure zinc layer is, the greater the resistance against the corrosion of the chlorides.
Abstract
Corrosion of galvanized reinforcements in concrete is controlled by three factors: the type of the cement, the type of metallographic structure and the humidity of conservation [...]
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Effect of four coating structures on corrosion kinetic of galvanized reinforcement in concrete
J. González, A. Vazquez, G. Jauregui, C. Andrade

Materials and Structures (1984). Vol. 17 (6), pp. 409-414

Abstract
In the present work is described the effect of the characteristics of the galvanized coating on corrosion rate of reinforcing bars embedded in a concrete without additives and in another with 2% CaCl2 in terms of cement weight. To this end, the following materials were subjected to the action of a moisture saturated atmosphere for a period of400 days: an annealed-galvanized coating; another one obtained by dipping in a molten Zn bath with0.025% Al and some others produced at450 and430°C in an ordinary bath. The attack evolution vs time was controlled by measuring the polarization resistance. The electrochemical determinations were gravimetrically verified and supplemented by a metallographic examination of tests coatings. In the absence of chlorides, the attack is fully tolerated. Chlorides radically change the corrosion behaviour of galvanized steel and increase the attack by a factor of2.8 in the most favourable case, but in these conditions, coatings with thick, homogeneous η layer outperform the usual ones, and specially the annealed ones.
Abstract
In the present work is described the effect of the characteristics of the galvanized coating on corrosion rate of reinforcing bars embedded in a concrete without additives [...]
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Corrosion of galvanized steel reinforcements in alkaline solutions: Part 2: SEM study and identification of corrosion products
A. Macías, C. Andrade

British Corrosion Journal (1987). Vol. 22 (2), pp. 119-130

Abstract
A report is presented of the morphology and composition of the corrosion products formed on galvanized corrugated steel reinforcing bars immersed in 0·05–1·5M KOH solutions designed to simulate concrete pore environments. The morphology was studied by SEM of the in situ corrosion products and optical examination of transverse sections of the bar; phase identification was performed by X-ray diffraction and IR absorption analyses. Passivation events on the corrosion potential and corrosion intensity curves can be related to precipitation of prismatic Zn (OH)2 crystals which form a compact layer on the surface. Active corrosion is associated with formation of porous ZnO layers or precipitation of Zn(OH)2 in the solution rather than on the galvanized surface. A solution-precipitation mechanism involving ZnO and Zn(OH)2− 4 intermediate species is proposed for formation of the passivating Zn(OH)2 coating, although this scheme must be complemented to take account of the localized corrosion observed at pH < 12 in the first part of this study
Abstract
A report is presented of the morphology and composition of the corrosion products formed on galvanized corrugated steel reinforcing bars immersed in 0·05–1·5M [...]
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Corrosion of galvanized steel in dilute Ca(OH) 2 solutions (pH 11·1–12·6)
A. Macías, C. Andrade

British Corrosion Journal (1987). Vol. 22 (3), pp. 162-171

Abstract
The corrosion behaviour of. galvanized bars was studied in 0·1–3 g Ca(OH)2 (pH 11·1–12·6) solutions designed to simulate the aqueous phase found in concrete pores. Corrosion potential and current density were monitored over the course of the 33 day tests and the corrosion products were examined by light and electron microscopy, X-ray diffraction, and IR absorption spectroscopy. Most specimens showed high initial corrosion rates which fell to a lower, nearly constant level after ∼6 days. The corrosion kinetics were found to depend only on solution pH. Ca2+ concentration had no effect other than on the nature of the corrosion products: Ca(Zn(OH)3)2.2H2O is the passivation product in the presence of calcium ions, Zn(OH)2 in their absence. Localized corrosion was observed at pH <11·5.
Abstract
The corrosion behaviour of. galvanized bars was studied in 0·1–3 g Ca(OH)2 (pH 11·1–12·6) solutions designed to simulate the aqueous phase [...]
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Corrosion of galvanized steel reinforcements in alkaline solutions: Part 1: Electrochemical results
A. Macías, C. Andrade

British Corrosion Journal (1987). Vol. 22 (2), pp. 113-118

Abstract
The behaviour of galvanized corrugated reinforcing bars has been studied in 0·001–1·5M solutions of KOH and NaOH designed to simulate aqueous environments found in concrete pores. Specimens were immersed for 33 days in polyethylene cells, corrosion potential, corrosion intensity, and pH being monitored throughout. Polarization curves were also obtained after 50 min and ∼ 33 days' immersion. It was possible to establish pH ranges in which localized corrosion (< 12), stability (12–13·4), and complete dissolution of the galvanic coating (> 13·4) occurred. A white, dusty corrosion product was observed on most specimens at the conclusion of the tests. Hydrogen dissolution on the galvanized bars occurred at pH values higher than the threshold level of 12·8±0·1.
Abstract
The behaviour of galvanized corrugated reinforcing bars has been studied in 0·001–1·5M solutions of KOH and NaOH designed to simulate aqueous environments [...]
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Equilibria of the chemical composition of the concrete pore solution. Part I: Comparative study of synthetic and extracted solutions
A. Moragues, A. Macías, C. Andrade

Cement and Concrete Research (1987). Vol. 17 (2), pp. 173-182

Abstract
A critical review is made on Frattini and Hansen's results on the equilibria of the different ions present in the aqueous solution of cement paste after mixing. These values are compared with those obtained from results of squeezed cement paste specimens drawing the conclusions that the cement paste solution is oversaturated in Ca(OH)2 just after mixing but the ions present in it are not in thermodynamic equilibrium because the solution is continuously evolving during early ages. Also the increase in the solubility of the Ca+2 ion because of the presence of SO4= is discussed and attributed to the increase in the ionic strength of the solution.
Abstract
A critical review is made on Frattini and Hansen's results on the equilibria of the different ions present in the aqueous solution of cement paste after mixing. These [...]
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Galvanized steel behaviour in Ca(OH)2 saturated solutions containing SO4 ions
A. Macías, C. Andrade

Cement and Concrete Research (1987). Vol. 17 (2), pp. 307-316

Abstract
In previous work on galvanized reinforcements in contact with Ca-containing highly alkaline media the authors have reported the existence of a threshold pH of 13.3 ± 0.1 below which the Zn in contact with such a medium is passivated, but at pH values above this it corrodes continuously until it totally disappears. In this paper, the influence of the presence of SO4 ions on the electrochemical behaviour of the galvanized has been studied. It has been established that the precipitation of CaSO4 with takes place in the media studied makes that the pH never surpasses the value of 13.3 ± 0.1. This coincidence with the pH threshold previously reported for passivation of the galvanized bars allows conclude that the sulfates not only are innocuous with respect to the galvanized behaviour in media which simulate the concrete but they are beneficial.
Abstract
In previous work on galvanized reinforcements in contact with Ca-containing highly alkaline media the authors have reported the existence of a threshold pH of 13.3 ± [...]
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Some unpublished results on the research in corrosion of steel in concrete
C. Andrade

Materials and Structures (1987). Vol. 20, pp. 153-159
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Accuracy of different electrochemical laboratory techniques for evaluating corrosion rates of galvanized reinforcements
A. Marias, C. Andrade

(1987). Proceedings of the Fourth International Conference on Durability of Building Materials and Components Singapore, 4–6, pp. 516-522

Abstract
In the present paper the accuracy of three electrochemical laboratory techniques in order to evaluate the corrosion rate of galvanized rods inmersed in solutions which simulate the pore solution, is commented. The techniques used were: polarization resistance, electrochemical impedance and harmonic analysis. The corrosion intensity values obtained through these techniques were compared with the gravimetric ones. Values of constant B obtained through polarization curves and the harmonic analysis were compared.
Abstract
In the present paper the accuracy of three electrochemical laboratory techniques in order to evaluate the corrosion rate of galvanized rods inmersed in solutions which simulate [...]
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Equilibria of the chemical composition of the pore concrete solution Part II: Calculation of the equilibria constants of the synthetic solutions
A. Moragues, A. Macías, C. Andrade, J. Losada

Cement and Concrete Research (1988). Vol. 18 (3), pp. 342-350

Abstract
The chemical composition of synthetic solutions used to simulate the pore concrete solution was analyzed in Part I. It was not possible to match the experimental results obtained from concentration measurements of the ions present in the solutions with the results obtained from calculations based on the values of pK of Ca(OH)2 and CaSO4. The inconsistency between the experimental values and the theoretical calculations was attributed to the elevated concentrations that exist, and, therefore, the elevated ionic strength.The errors that are committed when applying the Debye-Huckel theory make it imprecise for proper calculations at such high concentrations. As an alternative the use of “apparent constants” is proposed. These are calculated from the values of the concentrations directly measured in the solutions.
Abstract
The chemical composition of synthetic solutions used to simulate the pore concrete solution was analyzed in Part I. It was not possible to match the experimental results obtained [...]
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Polypropylene Fibre Reinforced Concrete Air Permeability
M. Sanjuan-Barbudo, A. Moragues, B. Bacle, C. Andrade

MRS proceedings library (1991). Vol. 211 (71)

Abstract
The permeability of concrete to gases is of direct importance to the durability of concrete structures, because of carbon dioxide flowing through the concrete favour lime carbonation and reinforcing steel corrosion. Mortar with and without polypropylene fibres having water/cementitious ratios of 0.30, 0.35 and 0.40 and a cement/sand ratio of 1/1 were studied. Polypropylene dosage varied from 0.1 to 0.3% by volume of cement. The characterization of mortar permeability was made using cylindrical shaped samples (3 cm height and 15 cm diameter). These specimens were 28 days cured and then dried before the test. The addition of fibres results in a decrease of air permeability. Variation of the water/cement ratio is of lesser importance than fiber addition.
Abstract
The permeability of concrete to gases is of direct importance to the durability of concrete structures, because of carbon dioxide flowing through the concrete favour lime [...]
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The behaviour of galvanized steel in chloride-containing alkaline solutions-I. The influence of the cation
A. Macías, C. Andrade

Corrosion Science (1990). Vol. 30 (4-5), pp. 393-407

Abstract
The behaviour of galvanized reinforced bars (rebars) in chloride-contaminated concrete is a very controversial matter not yet resolved. An extensive study of the behaviour of galvanized steel in alkaline solutions which simulate the aqueous phase present in concrete pores has been undertaken. This paper describes the modifications that the presence of chloride has on the corrosion behaviour of galvanized steel in alkaline solutions, as well as the influence of the accompanying cation. It was confirmed that the corrosion behaviour of galvanized steel in the presence of chlorides is controlled by the medium pH, which depends on the calcium or sodium salt which provides the chloride ions.
Abstract
The behaviour of galvanized reinforced bars (rebars) in chloride-contaminated concrete is a very controversial matter not yet resolved. An extensive study of the behaviour [...]
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Identificación de presencia de cemento aluminoso en hormigones mediante el uso del pachómetro
C. Andrade, J. Lozano, V. Seguí, E. Hernández

Informes de la Construcción (1992). Vol. 44 (419), pp. 65-70

Abstract
The observation of the premature degradations detected in High Alumina concretes due to the transformation and carbonation of this kind of cement has promoted the interest to develop in-situ testing methods for the fast Identification of HAC presence. In present work, preliminary results are given on the use of magnetic methods (pachometer), usually employed in the concrete cover verification, to identify the existence of HAC in a concrete. The laboratory results have been verified in practice and show that HAC can be clearly distinguished of an OPC concrete with the pachometer used in present experimentation. The research has also indicated that fly ash cements as aluminous one, have a lower magnetic reluctance. La constatación de los daños que se producen en estructuras de hormigón de cemento aluminoso, debido a su rápida transformación y carbonatación, ha llevado a intentar poner a punto diversos métodos de detección acelerada in situ de la presencia del citado cemento. En el presente trabajo se aportan unos primeros resultados sobre el empleo de métodos magnéticos (pachómetro) habituales en la medida del espesor del recubrimiento de armaduras para identificar si un hormigón está fabricado o no con cemento aluminoso. Los resultados de laboratorio se han contrastado en obra pudiéndose comprobar que el pachómetro utilizado es capaz de detectar perfectamente la presencia de aluminoso previa calibración con un hormigón de portland puro. Esta investigación preliminar también ha permitido comprobar que los hormigones de cenizas volantes presentan, como el aluminoso, una menor reluctancia magnética
Abstract
The observation of the premature degradations detected in High Alumina concretes due to the transformation and carbonation of this kind of cement has promoted the interest [...]
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A reply to the discussion by A. Xu and S. Chandra of the Paper “calculation of chloride diffusion coefficients in concrete from ionic migration measurements”
C. Andrade

Cement and Concrete Research (1994). Vol. 24 (2), pp. 380-384
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Calculation of chloride diffusion coefficients in concrete from ionic migration measurements
C. Andrade

Cement and Concrete Research (1993). Vol. 23 (3), pp. 724-742

Abstract
A critical review is offered on the Rapid Chloride Permeability Test standarized by AASHTO, pointing out its limitations and errors but recognizing its contribution to the developing of a simple and quick test for chloride migration. Then another review is made on the electrochemical fundaments of the processes developped in concrete when an electrical field is applied and on the basic equations of mass transport (Nernst-Plank and Nernst-Einstein) which can be applied to calculate ionic movements. The limitations and assumptions needed for a simplified resolution of these equations, are presented, as well as numerical examples of calculation of the Effective Diffusion Coefficient of chlorides, Deff, in steady state condition. Finally, considerations on the possibility of calculation of Deff from simple resistivity measurements are also offered.
Abstract
A critical review is offered on the Rapid Chloride Permeability Test standarized by AASHTO, pointing out its limitations and errors but recognizing its contribution to the [...]
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Suitability of Assessment Methods for Identifying Active and Passive Zones in Reinforced Concrete
J. González, P. Rodríguez, C. Andrade, M. Benito

Corrosion engineering (1995). Vol. 51 (2), pp. 145-152

Abstract
The ability of various electrochemical techniques to differentiate between areas of reinforcing steel (rebar) with high and low corrosion activity and to define the boundary between such areas was studied. These techniques are based on determining the corrosion potential (E[sub corr]), the galvanic current between an external stainless steel (SS) sensor and the bar (I[sub g]), the apparent polarization resistance (R[sub p][sup ap]), or the polarization resistance (R[sub p]) under electric confinement conditions. Values of E[sub corr] and I[sub g] (the current flowing between a SS counter electrode [CE] and the rebars) were shown to distinguish active areas from passive ones very well when the areas were isolated electrically, but with difficulty when the areas were in electric contact, which is usually the case. Values of R[sub p][sup ap] or i[sub corr] (both calculated using the Stern-Geary equation) were shown to define areas of high corrosion rates in a structure where passivity prevailed much better. However, excessive i[sub corr] values were estimated because the polarized area of the rebar (especially with passive rebars) was much greater than the CE area. Finally, the confinement of signal distribution permitted definition of the exact boundary between active and passive areas, regardless of whether they were isolated or interconnected. In addition, i[sub corr] values obtained with this technique were shown to provide a reliable quantitative index of the damage rate in reinforced concrete structures.
Abstract
The ability of various electrochemical techniques to differentiate between areas of reinforcing steel (rebar) with high and low corrosion activity and to define the boundary [...]
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La realcalinización y la extracción electroquímica de los cloruros en las construcciones de hormigón armado
L. Bertolini, F. Bolzoni, B. Elsener, C. Andrade

Materiales de Construcción (1996). Vol. 46 (244), pp. 45-55

Abstract
Realkalisation and electrochemical chloride removal techniques, developed for rehabiliting carbonated and chloride-containing structures, are presented. Electrolysis and electromigration mechanisms and consequences as well as electrochemical conditions at the reinforcement surface are discussed and compared with cathodic protection ones. Furthermore, possible side effects are commented. Se presentan técnicas electroquímicas de realcanización y extracción de cloruros, desarrolladas con el fin de rehabilitar estructuras carbonatadas y que contengan cloruros. Se discuten y comparan los mecanismos y consecuencias de la electrólisis y la electromigración, así como las condiciones electroquímicas en la superficie de las armaduras con los de protección catódica. Se comentan, también, los posibles efectos secundarios.
Abstract
Realkalisation and electrochemical chloride removal techniques, developed for rehabiliting carbonated and chloride-containing structures, are presented. Electrolysis and electromigration [...]
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Mathematical modelling of a concrete surface skin effect on diffusion in chloride contaminated media
C. Andrade, J. Díez, C. Alonso

Advanced Cement Based Materials (1997). Vol. 6 (2), pp. 39-44

Abstract
Concrete skin is considered the closest zone to the surface of concrete cover of reinforcements. It usually has a different composition than the internal concrete due to phenomena such as contact with molds or segregation of aggregates. In addition, environmental actions induce a gradient of moisture along the cover depth. These circumstances sometimes produce an irregular chloride profile in the cover, which either exhibits a maximum of chloride content some millimeters inside the outer surface or sometimes shows an anomalously high chloride concentration right at the concrete surface. In the present paper, analytical modeling of chloride diffusion is used to study the relative influence of the skin thickness. This theoretical analysis aims to show that there are cases where, if the diffusivity of the skin and the bulk concrete are very different, an error is introduced when the “skin effect” is not accounted for. The clarification of this error may contribute to understanding the differences found between laboratory experiments and the long-term record of chloride profiles in the same concrete.
Abstract
Concrete skin is considered the closest zone to the surface of concrete cover of reinforcements. It usually has a different composition than the internal concrete due to phenomena [...]
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Evolution of pH during in-situ leaching in small concrete cavities
A. Sagues, E. Moreno, C. Andrade

Cement and Concrete Research (1997). Vol. 27 (11), pp. 1747-1759

Abstract
Small amounts (0.4 cc) of neutral water placed in small cylindrical cavities (5 mm diameter) in concrete exposed to 100% relative humidity first developed a pH comparable to that of a saturated Ca(OH)2 solution. The pH then increased over a period of days-weeks toward a higher terminal value. A micro pH electrode arrangement was used. This behavior was observed in samples of 12 different concrete mix designs, including some with pozzolanic additions. The average terminal cavity pH closely approached that of expressed pore water from the same concretes. A simplified mathematical model reproduced the experimentally observed behavior. The model assumed inward diffusional transport of the pH-determining species in the surrounding concrete pore solution. The experimental results were consistent with the model predictions when using diffusion parameters on the order of those previously reported for alkali cations in concrete. The cavity size, cavity water content, and exposure to atmospheric CO2 should be minimized when attempting to obtain cavity pH values approaching those of the surrounding pore water.
Abstract
Small amounts (0.4 cc) of neutral water placed in small cylindrical cavities (5 mm diameter) in concrete exposed to 100% relative humidity first developed a pH comparable [...]
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Progress Report 1994-97
C. Andrade

Materials and Structures (1998). Vol. 31 (3), pp. 153-157
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L Aniversario
D. Ribé, C. Nombela, C. Andrade, F. Aguirre, M. Fisac, V. Mas, Á. García

Informes de la Construcción (1998). Vol. 50 (456-457), pp. 3-13

Abstract
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Editorial
C. Andrade

Informes de la Construcción (1999). Vol. 51 (462), p. 3
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An accelerated leaching test to evaluate the long term behaviour of concrete in waste disposal
A. Hidalgo, C. Andrade, C. Alonso

L'industria Italiana del Cemento (2001). Vol. 766, pp. 498-507

Abstract
The present work describes an accelerated leaching method that with a rapid process allows to develop and evaluate cements for use in a nuclear disposal, and the understanding of the long term effects. The method has been developed to study the stability of cementitious materials in contact with bentonite, to be used in high level radioactivity waste repositories, assuming that granitic water will be the leachant agent. Nitric and carbonic acids have been selected to induce the accelerated acid attack on pastes. Results have indicated the more aggressive character of carbonic acid and the suitability of the acid neutralisation to find out the alkaline reserve of the different tested pastes.
Abstract
The present work describes an accelerated leaching method that with a rapid process allows to develop and evaluate cements for use in a nuclear disposal, and the understanding [...]
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Towards excellence
S. Shah, C. Andrade

Materials and Structures (2002). Vol. 35 (8), p.446

Abstract
Progress has been made in American public education in the last 20 years, and the pending American Defense Education Act, inspired by the National Defense Education Act, would enable school districts to address many of the current problems of public schools. (MSE)
Abstract
Progress has been made in American public education in the last 20 years, and the pending American Defense Education Act, inspired by the National Defense Education Act, would [...]
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Statements and Conclusions
L. Amleh, C. Andrade, N. Buenfeld, B. Buhr

(2003). Life-Cycle Cost Analysis and Design of Civil Infrastructures Systems, pp. 432-439

Abstract
Engineers have been dealing with deterioration in concrete structures since shortly after their initial use. Before 1980 deterioration was taken into consideration predominantly using rules of thumb developed through experience. After 1980 simple engineering models, such as Fick's law, the Hetek's model and time dependent models, were developed and became more widely used. With time these models, both deterministic and stochastic, are becoming increasingly more sophisticated and are increasingly based on "physical" parameters. This trend will continue and future models will be based even more so on the physical, chemical and mechanical laws and principles that govern material and structural behaviour.
Abstract
Engineers have been dealing with deterioration in concrete structures since shortly after their initial use. Before 1980 deterioration was taken into consideration predominantly [...]
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Evaluacion del comportamiento a largo plazo de hormigones en almacenamientos de residuos radiactivos de alta actividad
A. Hidalgo, L. Fernández, S. Petit, C. Alonso, C. Andrade

Boletin de la Sociedad Española de Cerámica y Vidrio (2004). Vol. 43 (2), pp. 548-586

Abstract
The present work describes an accelerated leaching method that with a rapid process allows to develop and evaluate cements for use in a nuclear disposal, and the understanding of the long term effects. The method has been developed to study the stability of cementitious materials in contact with bentonite, to be used in high level radioactivity waste repositories. Nitric acid has been selected to simulate in an accelerated way the pH decreasing produced when concrete is in contact with groundwaters. Evaluacion del comportamiento a largo plazo de hormigones en almacenamientos de residuos radiactivos de alta actividad El presente trabajo describe un ensayo acelerado de lixiviación, que mediante un proceso rápido, permite desarrollar y evaluar cementos para su uso en instalaciones nucleares, y la comprensión de su comportamiento a largo plazo. El método se ha desarrollado para estudiar la estabilidad de materiales de base cemento, en contacto con bentonita, que serán utilizados en almacenamientos de resíduos radiactivos de alta actividad. Como agente lixiviante se seleccionó el ácido nítrico, con objeto de simular de forma acelerada, la disminución del pH que se produce cuando el hormigón entra en contacto con aguas subterráneas.
Abstract
The present work describes an accelerated leaching method that with a rapid process allows to develop and evaluate cements for use in a nuclear disposal, and the understanding [...]
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Are service life models appropriate for use in design of reinforced concrete structures for exposure to chloride salts?
C. Andrade

(2004). Third International RILEM Workshop on Testing and Modelling Chloride Ingress into Concrete Editor(s): C. Andrade and J. Kropp Print-ISBN: 2-912143-48-9, pp. 93-104

Abstract
Chloride ingress leading to corrosion of embedded steel is the most detrimental process affecting the durability of reinforced concrete structures. Various authors have suggested methods of calculating the time to depassivation of reinforcing steel by modelling chloride penetration on the basis of a solution of Fick's second law of diffusion. This involves several assumptions, including boundary and initial conditions that may be fulfilled in idealised laboratory tests but not in real structures. The situation calls for an explicit recognition of the limited knowledge that exists regarding both detailed mechanisms of chloride ingress and threshold chloride concentrations that cause depassivation of steel in different types of concrete subjected to different conditions of exposure. These uncertainties can result in major inaccuracies when models are used to predict the long-term performance of structures. Despite the admitted lack of detailed understanding of the process of chloride penetration, tentative proposals are outlined for alternative methods of determining performance indices useful in some circumstances for specifying the durability of structures exposed to chloride salts. They depend on measurement of one parameter (steady-state diffusion coefficient or electrical resistivity) to account for the transport process and a separate parameter to account for chloride binding. The values obtained provide a means of ranking different types of concrete in terms of their expected performance when exposed to chloride environments in which diffusion is likely to be the dominant transport mechanism.
Abstract
Chloride ingress leading to corrosion of embedded steel is the most detrimental process affecting the durability of reinforced concrete structures. Various authors have suggested [...]
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Model for prediction of reinforced concrete service life based on electrical resistivity
C. Andrade

IBRACON Mater J. (2005). Vol. 1, pp. 1-5

Abstract
Reinforcement corrosion is attracting research interest in many areas due to the economical consequences of the damage generated by the process. Several proposals can be found on prediction of the time to reinforcement corrosion and service life duration. In present communication a proposals is made on using the electrical resistivity to calculate both the initiation and propagation periods. For the time to corrosion onset, the electrical resistivity represents the porosity and its connectivity and therefore can be used to model transport processes. Due to the reaction of chlorides and carbon dioxide with cement phases, the resistivity has to be factorised by a “reaction factor” accounting for it. Concerning the propagation period, the electrical resistivity is an indication of the moisture content of concrete and therefore, it has a certain relationship with the corrosion cement. The service life can be expressed with the following equation: corr x ef Cl CO es ClCO l i p k P k x r t t t ρ ·ρ 2 2 , 2 = + = + Based in it, minimum resistivity values can be established according to cover thickness and in function of exposure classes.
Abstract
Reinforcement corrosion is attracting research interest in many areas due to the economical consequences of the damage generated by the process. Several proposals can be found [...]
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Reinforced-concrete cover cracking due to the pressure of corrosion products
A. Muñoz, C. Andrade, A. Torres-Acosta

Proceedings of the 6th International Conference on Fracture Mechanics of Concrete and Concrete Structures (2007). Vol. 3, pp. 1857-1864

Abstract
Reinforcement corrosion is one of the most important phenomena that reduce the service life of the reinforced concrete structures. Steel corrosion reduces the strength and bond of the reinforcement and the oxides formed cause internal stresses that crack the concrete cover. The prediction of the evolution of these effects is a problem that involves chemical and mechanical aspects. The phenomenon is not well known and quantitative descriptions of development and magnitude of stresses produced by a corroding rebar to concrete are scarce and although there are several models in the literature they do not universally reproduce the experimental results. This work presents a summary of the available experimental evidence on the amount of internal expansion needed at the reinforcement level for concrete cover to crack and formulas to estimate the expansion. Also, results are presented on the pressure needed for concrete cover to crack together with the experimental technique used for the verification of the assumptions and crack propagation analysis.
Abstract
Reinforcement corrosion is one of the most important phenomena that reduce the service life of the reinforced concrete structures. Steel corrosion reduces the strength and [...]
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Elasto-plastic model for beams damaged by corrosion
M. Prieto, A. Muñoz, C. Andrade

Revue Européene de Génie Civil (2007). Vol. 11 (1-2), pp. 163-178

Abstract
This article describes the elasto-plastic model that has been applied to analyse the beams damaged by corrosion. CONTECVET Manual, which contains the principles of this kind of structural evaluation, has been adopted. This Manual recommends considering the reduced section of the concrete and of the reinforcements as well as the possible reduction of the concrete steel bond. The first part of the article describes the basis of the structural model and, the mechanical behaviour of the materials. In the second part, the results of the experimental tests are presented and compared with the results of the model. The results indicate an enough good accordance, if the typical scatter of this type of experimental tests is taken into account.
Abstract
This article describes the elasto-plastic model that has been applied to analyse the beams damaged by corrosion. CONTECVET Manual, which contains the principles of this kind [...]
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Structural Assessment of Corroded Beams
M. Prieto, A. Noval, C. Andrade

ECS Transactions (2010). Vol. 3 (13), pp. 20-42

Abstract
This paper shows how the corrosion and mechanical actions can be taken into account in a simple model for the assessment of structural elements. This work is framed in the Project Benchmark des Poutres de La Rance in which several partners have participated. The Project tried to characterize the degradation of reinforced and prestressed concrete structures after an aging in marine atmosphere with non-destructive methods and to evaluate different existing models for the structural assessment. For this aim a 4-point bending test was performed on six prestressed concrete beams. The model gives a reasonable approach for the assessment of structural elements. Similar rules can be adopted for other failure modes. It is important to notice the need of reliable input data for the assessment and also the need of integration of deterioration processes in design.
Abstract
This paper shows how the corrosion and mechanical actions can be taken into account in a simple model for the assessment of structural elements. This work is framed in the [...]
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Molecular Dynamics simulations of Hydrogen Embrittlement: preliminary results
J. Sánchez, P. Andrés, C. Andrade, J. Fullea

Anales de Mecánica de la Fractura. (2010).

Abstract
Hydrogen embrittlement is believed to be one of the main reasons for cracking of structures under stress. High strength steels in these structures often include a ferritic core made of alpha-iron (body centered cubic lattice). Previous work [1] was concerned with the interaction of atomic hydrogen with iron using first principles calculations. We studied the effect of interstitial hydrogen in the iron lattice and the stress induced by the interstitial hydrogen in the host lattice. In this paper we study the dynamical behaviour of hydrogen inside the iron lattice. Using ab-initio Molecular Dynamics we obtain hydrogen diffusion paths and by taking statistical averages we extract diffusion coefficients from Einstein’s equation. Depending on temperature, the diffusion path involve going through tetrahedral or octahedral sites. Simulations where a number of hydrogens occasionally coincide in one unit cell have been performed to elucidate the effect of interactions between hydrogens
Abstract
Hydrogen embrittlement is believed to be one of the main reasons for cracking of structures under stress. High strength steels in these structures often include a ferritic [...]
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Estudio del efecto sumidero de CO2 de los materiales de base cemento
I. Galan, C. Andrade, M. Prieto, P. Mora, J. López, M. Sanjuan-Barbudo

Cemento y Hormigón (2010). Vol. 939, pp. 70-83

Abstract
Uno de los principales problemas relacionados con el cambio climático es el efecto invernadero, producido por la absorción parcial de la radiación infrarroja emitida por la Tierra por parte de los gases denominados "de efecto invernadero", entre los que se incluye el dióxido de carbono. El trabajo aquí planteado se enmarca dentro de las iniciativas acometidas por la industria del cemento para contribuir a la reducción del efecto invernadero y los estudios realizados para estimar la contribución de los materiales de base cemento en la lucha contra el cambio climático. Para ello se estudia el alcance del efecto sumidero de CO2 que supone la carbonatación del hormigón. La Convención Marco de las Naciones Unidas sobre el Cambio Climático de 1992 recoge en su artículo 1 la definición de sumidero: "Por sumidero se entiende cualquier proceso, actividad o mecanismo que absorbe un gas de efecto invernadero, un aerosol o un precursor de un gas de efecto invernadero de la atmósfera".
Abstract
Uno de los principales problemas relacionados con el cambio climático es el efecto invernadero, producido por la absorción parcial de la radiación infrarroja [...]
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CO 2 sink effect of concrete carbonation
I. Galan, C. Andrade, P. Mora, J. López, M. Sanjuán, M. Prieto

Proceedings of Special Technical Sessions. Second International Conference on Sustainable Construction Material s and Technologies (2010).

Abstract
Although carbonation of cement phases is well known, the amount of carbon dioxide combined during the process has been much less investigated. Related to the greenhouse effect much more attention is being paid to the sinks for C02 in order to correctly compute the gases emission during production of materials. In the case of cement a strict calculation should discount the C02 emitted from that fixed by the concrete. This is the aim of present work which is a study of the cement based materials ability to combine C02. Using Thermogravimetry and Differential Thermal Analysis as well as phenolphthalein indicator, quantities of C02 combined and carbonation depth in several cement pastes and concretes exposed to different environments have been measured. A calculation to estimate the contribution of cement based materials carbonation to the partial re-absorption of the C02 emitted in cement production is proposed.
Abstract
Although carbonation of cement phases is well known, the amount of carbon dioxide combined during the process has been much less investigated. Related to the greenhouse effect [...]
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The use of electrical resistivity as a NDT for the specification of concrete durability
C. Andrade

Proceedings of 6th international conference on concrete under severe conditions (CONSEC '10) (2010).

Abstract
The calculation of the time to reinforcement corrosion and service life dura-tion is a subject of increasing interest. In present communication is explained how to use the electrical resistivity to calculate both the initiation and propagation periods in the case of carbonation and chloride penetration, although only the case of chlorides is illustrated here. The main advantage is that resistivity is an inexpensive non destructive measurement that can be used for routine quality control. The resistivity is an indication of the porosity and pore connectivity. It increases with time as hydration proceeds which is an indication of aging or pore refinement. In addition to the measurement of the resistivity it is necessary to calculate a "reaction factor" for accounting of the binding with cement phases. Concerning the propagation period, the electrical resistivity is an indication of the moisture content of concrete and therefore, it has a relationship with the corrosion cement. A model is proposed in which the resistivity is introduced in the square root of time law.
Abstract
The calculation of the time to reinforcement corrosion and service life dura-tion is a subject of increasing interest. In present communication is explained how to use the [...]
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Correlación entre ancho de grieta del recubrimiento del concreto y corrosión del refuerzo en elementos expuestos a un ambiente natural contaminado por cloruros
C. Andrade, A. Muñoz, A. Torres-Acosto

Concreto y cemento (2010). Vol. 1 (2), pp. 30-41

Abstract
La corrosión del refuerzo genera daños variados a estructuras de concreto que influyen en la capacidad de carga; entre estos daños se puede mencionar el agrietamiento del recubrimiento del concreto. Este trabajo proporciona resultados de campo en el tema de propagación de grietas del recubrimiento del concreto por corrosión del refuerzo después de una exposición natural por varios años. Los elementos estructurales evaluados fueron una viga T y una columna cuadrada expuestos al ambiente atmosférico de Madrid, España. Dos formulas empíricas fueron usadas para correlacionar los valores obtenidos del agrietamiento del recubrimiento por corrosión: w=k Px/(C/φ), y w=k Px/Ro, en donde w es el ancho de la grieta por corrosión, k es una constante de proporcionalidad, Px es la penetración por la corrosión en el tiempo, C/φ es la relación recubrimiento de concreto/diámetro del refuerzo, y Ro es el radio original del refuerzo.
Abstract
La corrosión del refuerzo genera daños variados a estructuras de concreto que influyen en la capacidad de carga; entre estos daños se puede mencionar [...]
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Determination of chloride diffusivity through partially saturated Portland cement concrete by a simplified procedure
A. Guimarães, M. Climent, G. Vera, F. Vicente, C. Andrade

Control and Building Materials (2011). Vol. 25 (2), pp. 785-790

Abstract
A recently proposed methodology for measuring the diffusion coefficient of chloride ions through concrete partially saturated with water, has been applied to five high-early-strength Portland cement mortars. The method is based on putting solid NaCl in contact with the concrete surface during the diffusion test. The results obtained indicate a strong dependence of the diffusion coefficient on the water saturation degree. The ionic diffusivities through these mortars are higher than those obtained with the same approach for five pozzolanic cement mortars of similar compositions. It has been also shown that the proposed test methodology and a different one based on the interaction of HCl(g) with the tested concrete surface, can yield comparable results. The D values obtained are of similar magnitude, and the same type of dependence on the water saturation degree is found through both methods, when applied to similar Portland cement concrete mixes with cement content of about 350 kg/m3 and water/cement ratios between 0.5 and 0.6.
Abstract
A recently proposed methodology for measuring the diffusion coefficient of chloride ions through concrete partially saturated with water, has been applied to five high-early-strength [...]
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Bond Response in Structural Concrete with Corroded Steel Bars. Experimental Results
M. Prieto, P. Tanner, C. Andrade

(2011). Modelling of Corroding Concrete Structures. RILEM Bookseries, vol 5, pp.231-241. Springer, Dordrecht

Abstract
The growing interest in upgrading existing reinforced concrete structures or extending their service life, and in ensuring greater durability in new designs, has led to a need for resistance models that take deterioration processes into account to verify structural safety. Bond activation between reinforcing steel and concrete is of cardinal importance in this context. A number of experimental studies have been conducted in recent years on bond failure, which normally leads to brittle behaviour. The findings have diverged rather widely, however, due primarily to differing test conditions. The present paper presents an experimental programme for eccentric pull-out tests in which specimens were subjected to both accelerated and natural corrosion in an attempt to surmount these inconsistencies. It also introduces an embedded fibre-optic sensing system with corrosion-resistant fibre Bragg grating sensors and discusses some of the findings.
Abstract
The growing interest in upgrading existing reinforced concrete structures or extending their service life, and in ensuring greater durability in new designs, has led to a [...]
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Corrosion Resistance Performance of Steel-Reinforced Engineered Cementitious Composite Beams
M. Sahmaran, V. Li, C. Andrade

Materials Journal (2008). Vol. 105 (3), pp. 243-250

Abstract
This paper presents the results of an experimental investigation on steel-reinforced engineered cementitious composite (ECC) beams subjected to accelerated corrosion by an electrochemical method. ECC is a micromechanically-based designed, high-performance, fiber-reinforced cementitious composite with high ductility and improved durability due to tight crack width. An accelerated corrosion test method, which was carried out by imposing a constant potential, was used to induce different degrees of corrosion into the reinforcement embedded in ECC prismatic specimens. Mortar specimens that have an equal compressive strength to the ECC specimens were also used as reference specimens. After inducing different degrees of accelerated corrosion, the cracks and the residual flexural load capacity of the test specimens and the mass loss of reinforcing bars embedded in specimens were determined. From the results of this study, it is concluded that due to its high tensile strain capacity and microcracking behaviors, ECC significantly prolonged the corrosion propagation period while enhancing the ability to maintain the load capacity of the beam. These performances of reinforced ECC (R/ECC) are expected to contribute substantially to improving infrastructure sustainability by reducing the amount of repair and maintenance during the service life of the infrastructure.
Abstract
This paper presents the results of an experimental investigation on steel-reinforced engineered cementitious composite (ECC) beams subjected to accelerated corrosion by an [...]
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Hydrogen induced changes in structural properties of iron: Ab initio calculations
A. Castedo, J. Sánchez, J. Fullea, C. Andrade, P. Andrés

(2011). Advances in Modeling Concrete Service Life. RILEM Bookseries, Vol 3, pp. 79-84. Springer, Dordrecht

Abstract
We have used Ab initio calculations to study the structural changes produced by the inclusion of light impurities into pure bcc iron. In order to obtain a clear picture of the mechanics of the phase changes Bain’s pathway was studied in detail for pure iron. The position that hydrogen atoms tend to occupy at high densities favours octahedral sites inside the bcc matrix, producing an internal stress field that suggests a deformation that matches the prediction of martensitic transformation predicted by Bain’s pathway. We have used Density Functional Theory in order to optimize the structures studied, obtaining the enthalpy of the configuration as a function of c/a, allowing a better understanding of the dynamics of the process of phase changes.
Abstract
We have used Ab initio calculations to study the structural changes produced by the inclusion of light impurities into pure bcc iron. In order to obtain a clear picture of [...]
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Steel Corrosion in a Chloride Contaminated Concrete Pore Solution with Low Oxygen Availability
L. Toro, C. Andrade, J. Fullea, I. Martínez, N. Rebolledo

(2011). Advances in Modeling Concrete Service Life. RILEM Bookseries, vol 3, pp. 53-63. Springer, Dordrecht

Abstract
It is commonly mentioned that in concrete chloride induced corrosion is controlled by the oxygen content in such a manner that in water saturated conditions no oxygen will be present and thus no corrosion can develop. In the present paper, experimentation has been made in low oxygen availability “pore” solutions with several amounts of chlorides. These situations may represent the case of a water saturated concrete. The results indicate that at very low oxygen contents, i.e. almost negligible because complete removal is very difficult, corrosion may develop in presence of chlorides. The presence or absence of corrosion is influenced by the amount of chloride, its corrosion potential and the steel surface condition.
Abstract
It is commonly mentioned that in concrete chloride induced corrosion is controlled by the oxygen content in such a manner that in water saturated conditions no oxygen will [...]
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From the instantaneous corrosion rate to a representative value
C. Andrade, N. Rebolledo, F. Pedrosa

ICCRRR 2012 (2012).

Abstract
Reinforcement corrosion develops due to the penetration of chlorides or of the carbonation front through the concrete pores and corrosion develops if enough moisture is present. However as the corrosion rate changes with temperature and the evolution of the corrosion itself, the representation may not be clear enough to be used for comparative purposes or for prediction of future evolution. The present work proposes a parallel use of accumulated corrosion depth, which is obtained by the integration of each age of the corrosion rate-time curve. This kind of representation enables the determination of corrosion depth at each age and appears the adequate to establish a Representative annual average value for comparative purposes. The procedure is applied to concrete specimens and real size elements exposed to Madrid outdoor conditions.
Abstract
Reinforcement corrosion develops due to the penetration of chlorides or of the carbonation front through the concrete pores and corrosion develops if enough moisture is present. [...]
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Corrosión y protección de armaduras
C. Andrade

Informes de la Construcción (1982). Vol. 33 (339), pp. 33-41

Abstract
La investigación en el campo de la corrosión de armaduras ha ido siempre muchos años con retraso respecto de los avances conseguidos en otros campos de la corrosión del acero, principalmente por la dificultad que supone el manejo de un electrólito (fase acuosa) que está encerrado en los poros de una estructura pétrea que dificulta el seguimiento visual de los procesos. Electrólito que evoluciona constantemente en el tiempo debido a la progresiva hidratación del cemento y, por lo tanto, no presenta una composición definida y fácilmente reproducible en todos sus componentes.
Abstract
La investigación en el campo de la corrosión de armaduras ha ido siempre muchos años con retraso respecto de los avances conseguidos en otros campos de [...]
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Determinación electroquímica cuantitativa de la velocidad de corrosión de un acero de construcción. Evaluación de la susceptibilidad al ataque por picaduras. Parte II: Ensayos en mortero
C. Andrade, J. González

Materiales de Construcción (1978). Vol. 28 (169), pp. 49-62

Abstract
El estudio del efecto de un determinado aditivo sobre la corrosión de las armaduras, o el de un hormigón con fisuras, o sometido a ambientes marinos o, en fin, de cualquier factor o circunstancia calificada como agresiva, suele exigir un laborioso y extenso programa de trabajo que contemple todas las posibilidades por las que puedan pasar las armaduras y el hormigón que las contiene. En éste, como en tantos otros campos de la tecnología, es importante la búsqueda de métodos de ensayo acelerados, que sean a la vez de lo más representativos posible una ayuda para economizar esfuerzo y materiales.
Abstract
El estudio del efecto de un determinado aditivo sobre la corrosión de las armaduras, o el de un hormigón con fisuras, o sometido a ambientes marinos o, en fin, [...]
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Corrosión de armaduras embebidas en hormigón carbonatado
C. Andrade, S. Algaba, J. González

Materiales de Construcción (1981). Vol. 31 (181), pp. 45-53

Abstract
Los componentes ácidos de la atmósfera, en particular el CO2, pueden neutralizar (carbonatar) el electrólito que llena los poros del hormigón y las fases del clínker, transformándolos en variedades del CO3Ca. La carbonatación no sólo modifica la estructura de la pasta de cemento y por lo tanto sus propiedades, sino que también tiene una influencia decisiva sobre la velocidad de corrosión de las armaduras (1) (2). En un reciente informe del Comité 12-CRC de la RILEM (3) se afirmaba que: "si se exceptúa la corrosión causada por Cl-, actualmente se está de acuerdo en que la carbonatación del hormigón es la condición esencial para la corrosión de las armaduras". (Aquí se debería añadir que esto se aplica a los hormigones simplemente armados, pues en los pretensados también es muy peligroso el fenómeno conocido como corrosión bajo tensión). La carbonatación puede desencadenar el proceso de corrosión, debido a que el descenso de pH que provoca hace posible el paso de las armaduras del estado pasivo al activo. La velocidad de ataque depende, sin embargo, de otros factores externos: un contenido mínimo de humedad en el medio ambiente que garantice la existencia del electrólito en los poros del hormigón, y un libre acceso de O2 hasta la superficie metálica para que pueda producirse la semirreacción catódica. Numerosos autores están de acuerdo con estos puntos, pero sin aportar pruebas cuantitativas de los mismos. Es objeto principal de este trabajo contribuir a llenar este vacío.
Abstract
Los componentes ácidos de la atmósfera, en particular el CO2, pueden neutralizar (carbonatar) el electrólito que llena los poros [...]
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La agresividad ambiental y la durabilidad de las estructuras de hormigón
B. Perepérez, E. Barberá, C. Andrade

Informes de la Construcción (2012). Vol. 38 (388), pp. 17-24

Abstract
The deterioration of concrete structures is the result of the interaction between them and the environment. In this study, comments are made on the most decisive environmental factors and their interactions. Special reference is made to the corrosion of the reinforcements and also to the different proposals of classification of the aggressiveness. El deterioro de las estructuras de hormigón es el resultado de la interacción entre ellas y el medio ambiente. En el presente trabajo se comentan los factores ambientales más determinantes y sus interacciones, con especial referencia a la corrosión de las armaduras, así como diferentes propuestas de clasificación de la agresividad.
Abstract
The deterioration of concrete structures is the result of the interaction between them and the environment. In this study, comments are made on the most decisive environmental [...]
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Corrosión de armaduras galvanizadas y sin proteger embebidas en cemento aluminoso estabilizado
M. Pérez, F. Triviño, C. Andrade

Materiales de Construcción (2012). Vol. 31 (182), pp. 49-68

Abstract
El cemento aluminoso, cuya obtención se basa en la fusión de bauxita y caliza, ha demostrado desde que fue patentado en Francia, en 1908 por Cementos Lafarge, unas propiedades excepcionales que lo hacen idóneo para ciertas aplicaciones. Tales propiedades son fundamentalmente el desarrollo de elevadas resistencias mecánicas en las primeras edades de hidratación, posibilidad de hormigonar en tiempo frío, una gran resistencia química al agua de mar y a los sulfatos, propiedades refractarias, etc. Todo ello hizo que el cemento aluminoso del tipo fundido, con un 40 % de Al2O3, se utilizara ampliamente en la construcción. Sin embargo, a partir de un determinado momento empezaron a observarse alteraciones en algunas obras construidas con hormigón de este tipo, manifestándose importantes pérdidas de sus resistencias mecánicas (1). Las causas de tales deterioros han sido ampliamente estudiadas (2)-(13), atribuyéndose la principal a la "conversión" de los aluminatos cálcicos hidratados hexagonales en hidratos cúbicos, según reacción [1]
Abstract
El cemento aluminoso, cuya obtención se basa en la fusión de bauxita y caliza, ha demostrado desde que fue patentado en Francia, en 1908 por Cementos Lafarge, [...]
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Estudio por SEM de los productos de corrosión de armaduras galvanizadas sumergidas en disoluciones de pH comprendido entre 12,6 y 13,6
M. Blanco-Varela, C. Andade, A. Macías

Materiales de Construcción (2012). Vol. 34 (195), pp. 55-66

Abstract
In previous work on galvanized reinforcements in contact with Ca-containing highly alkaline media, the authors have reported the existence of a threshold pH below whith such a medium is passivated, but at pH values above this it corrodes continuously until it totally disappears. In this paper, after a brief literature review concerning the identification of the corrosion products in these media, they report that the passivation detected from the data of the polarisation technique agreed with the results of an SEM study. They show that below the threshold pH value the surface is covered with a continuous layer of calcium hydroxyzincate, Ca[Zn(0II)j2-^ HjO, and above this pH, the layer increase its proportion of non-passivating ZnO, to the detriment of the calcium hydroxyzincate contents. They have also established that it is the (Ca^'^) ions that control the amount of calcium hydroxizincate formed, and therefore the likelihood of the formation of a continuous passivating layer. Finally, they report that if the calcium hydroxyzincate is perfectly developed, a later increase of the pH does not affect the stability.
Abstract
In previous work on galvanized reinforcements in contact with Ca-containing highly alkaline media, the authors have reported the existence of a threshold pH below whith such [...]
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Durabilidad de las armaduras en el sistema Dragados-Plastbau
C. Andrade, J. Rodríguez

Informes de la Construcción (2012). Vol. 38 (383), pp. 49-53

Abstract
En un sistema de las características del presente, los elementos metálicos que pueden sufrir corrosión son principalmente la malla y los conectores que atraviesan el poliestireno. La porosidad del microhormigón y el no siempre suficiente espesor de recubrimiento pueden permitir una carbonatación del microhormigón que alcance la malla durante el período de vida útil previsto para la estructura. Este riesgo de corrosión por carbonatación viene acrecentado en este sistema particular por una posible aparición de fisuras (retracción, movimientos de dilatación y asentamientos diferenciales, etc.).
Abstract
En un sistema de las características del presente, los elementos metálicos que pueden sufrir corrosión son principalmente la malla y los conectores que [...]
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La importancia del curado en el comportamiento posterior frente a la corrosión de las estructuras de hormigón armado
W. López, S. Feliu, J. González, C. Andrade

Materiales de Construcción (2012). Vol. 41 (223), pp. 5-17

Abstract
Steel in contact with fresh concrete is covered by a layer of passivating oxydes due to the alkaline nature of the pore solution. The presence of oxygen plays an important role in this passivation process as well as in the corrosión one when is developped due to the ingress of aggressives, such as, chioride ions. In the present paper, results are commented on the behaviour found when oxygen is limited due to the concrete curing conditions, in a completely saturated chamber Surprisely, the results indícate that the oxygen availability during the curing has a marked influence on the future corrosión beabieviour This allows to deduce that the mechanisms involved are not so simple as was currently accepted and that new specific tests are needed to clarify the controversial points.
Abstract
Steel in contact with fresh concrete is covered by a layer of passivating oxydes due to the alkaline nature of the pore solution. The presence of oxygen plays an important [...]
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Corrosión del acero desnudo y galvanizado en yeso
M. Gómez, C. Andrade

Materiales de Construcción (2012). Vol. 38 (212), pp. 5-20

Abstract
Gypsum is a relatively lovi/-cost building material much abounding in our country. When it is put in contact with steel, it may produce high corrosion rates due to its pH value (close to 7). This work reports the results obtained in studying the corrosion rates of bare and galvanized steel in contact with gypsum and plaster, as well as the influence curing thermal treatment applied to gypsum, enviromental relative humidity and addition of compounds with different natures and purposes may have in such process. In-situ observations, as well as the measurement of the Polarization Resistance and the weight loss have been used as measurement technics. From the results obtained it has been possible to deduce that galvanized steel has better behaviour in dry enviroments than bare steel in the same conditions and moist atmosphere induces proportionally more corrosion in galvanized steel than in bare one. Additions to gypsum do not modified these conclusions, though it may be pointed out that addition of nitrites or lime improves the behaviour of bare steel, while galvanized behaviour is not modified. The addition of lime is not recommended because phenomena of dilated along time expansion may take place.
Abstract
Gypsum is a relatively lovi/-cost building material much abounding in our country. When it is put in contact with steel, it may produce high corrosion rates due to its pH [...]
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Influencia del contenido en álcalis de los cementos sobre la corrosión de armaduras galvanizadas
C. Andrade, A. Macías

Materiales de Construcción (2012). Vol. 31 (184), pp. 83-93

Abstract
Las armaduras galvanizadas han mostrado un comportamiento errático en los ensayos llevados a cabo hasta ahora, encontrándose en la literatura datos muy contradictorios. Los autores han encontrado que las siguientes tres variables tienen una decisiva importancia: a) pH del mortero u hormigón, que depende básicamente de la cantidad de álcalis del cemento, b) tipo de estructura metalográfica del recubrimiento galvanizado, que depende principalmente del tipo de acero y su contenido en Si y C, y c) la humedad contenida en los poros del hormigón. En este trabajo se presentan resultados relacionados sólo con el punto a). Se ha podido comprobar que existe un valor de pH umbral o crítico por encima del cual el recubrimiento galvanizado se corroe severamente, debido a la formación de capas no-protectoras de productos de corrosión. La evolución de la velocidad de corrosión se ha seguido mediante la Resistencia de Polarización, y las pérdidas de peso se han determinado también, gravimétricamente
Abstract
Las armaduras galvanizadas han mostrado un comportamiento errático en los ensayos llevados a cabo hasta ahora, encontrándose en la literatura datos muy contradictorios. [...]
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Estabilidad de la capa de hidroxizincato cálcico formada en las armaduras galvanizadas ante un posterior aumento del valor del pH
A. Macías, C. Andrade

Materiales de Construcción (2012). Vol. 36 (204), pp. 19-28

Abstract
In previous works on galvanized reinforcements in contact with Ca- containing highly alkaline media, the authors have reported the existence of a threshold pH of 13,3 ± 0,1, below which the Zn in contact with such a medium is passivated by formation of a continuous layer of calcium hydroxyzincate, but at pH values above this it corrodes continuously until it totally disappears. The investigation on the stability of the calcium hydroxyzincate layer after an increase of the pH to very high alkaline values, is the aim of the present paper. It has been establised that if the calcium hydroxyzincate is perfectly developed, a later increase of the pH does not affect the stability.
Abstract
In previous works on galvanized reinforcements in contact with Ca- containing highly alkaline media, the authors have reported the existence of a threshold pH of 13,3 ± [...]
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Corrosión de armaduras y su inspección en hormigones de cemento aluminoso
C. Andrade

Informes de la Construcción (2012). Vol. 44 (422), pp. 39-48

Abstract
Until recently has not become evident the magnitude of the problem that the corrosion of the reinforcement supposes for concrete technology. That is why, when aluminous cement preliminary degradations appeared it was not foreseen the dimension of future consequences..Now, the long term difficulty that aluminous cement presents is, in addition to the loss in mechanical strength, the possible corrosion of reinforcement. In present work are described aspects related to the processes which may originate the corrosion and given are some practical indications on how evaluate it.
Abstract
Until recently has not become evident the magnitude of the problem that the corrosion of the reinforcement supposes for concrete technology. That is why, when aluminous cement [...]
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Tendencias actuales en la investigación sobre corrosión de armaduras
C. Andrade

Informes de la Construcción (2012). Vol. 40 (398), pp. 7-14

Abstract
During the last 20 years, the corrosion of concrete rebars is increasily being considered a major problem due the high costs spent by some Governments on repair and of civil concrete structures. In the present paper, a brief description on the causes of this type of corrosion is offered together with some references to the costs of repairing of bridge decks published by USA researchs. Finally, the main lines of research which, in opinion of the authors have priority, are commented.
Abstract
During the last 20 years, the corrosion of concrete rebars is increasily being considered a major problem due the high costs spent by some Governments on repair and of civil [...]
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Análisis de las condiciones de fisuración en las estructuras de hormigón armado y su relación con la probabilidad de corrosión de las armaduras
J. Rodríguez, C. Andrade

Informes de la Construcción (2012). Vol. 36 (366), pp. 37-52

Abstract
Cracks appears in reinforced concrete structures as something inherent to the material they are composed. Causes of diverse kind advise to control this cracking, considering it can not be prevented. The durability of reinforcements is, till now, the reason that has determined, in most structures, the study and the control of this cracking. In this report, the information contained in certain standards in force (CP-110; ACI-318-83; B.A.E.L. 80; MODEL CODE AND EH-82) about the characteristics the concrete must have and about the cracking in pieces of reinforced concrete under pliability attempts, are analysed and resumed, trying to judge later its connection with the corrosion phenomenon in reinforcements
Abstract
Cracks appears in reinforced concrete structures as something inherent to the material they are composed. Causes of diverse kind advise to control this cracking, considering [...]
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Testing and modelling chloride penetration into concrete
M. Prieto, P. Tanner, C. Andrade, F. Tavares, R. D'Andrea

Construction and Building Materials (2013). Vol. 39, pp. 9-18

Abstract
The design of concrete structures is usually made by means of a performance approach based on strength tests carried out following testing conditions agreed by convention. A similar approach should also be followed in the case of durability design regarding reinforcement corrosion. This type of consideration enables the establishment of verification of durability in categories. Three categories have been identified: (I) it would be the prescriptive method already given in present codes based on “deemed-to-satisfy” rules, (II) this is based in the testing through “durability indicators” that where still not quantification of the time to reach a limit state is explicit but the minimum life time is assured through performance based tests, (III) it is the category in which the calculation of aggressive ingress through models having explicit the time is made including probabilistic treatments. In the paper in addition to the comment on the most common methods of calculation of the chloride ingress and their limitations it is illustrated how for level II and III the measurement of the electrical resistivity results a very suitable proposal due to this parameter can be measured in a non-destructive test and serves to quality control. It is not only a performance test (level II) but it can be included in models of both the initiation and propagation periods. For the time to corrosion onset, the electrical resistivity represents the porosity and its connectivity and therefore can be used to model transport processes. It also results very suitable for measuring concrete aging and then accounting for the reduction of the diffusion coefficient with time. Concerning the propagation period, the electrical resistivity is an indication of the moisture content of concrete and therefore, it has a certain relationship with the corrosion cement. A model is proposed in which the resistivity is introduced in the square root of time law. Finally the paper comments on the tests methods used for the measurement of the diffusion coefficient and of resistivity
Abstract
The design of concrete structures is usually made by means of a performance approach based on strength tests carried out following testing conditions agreed by convention. [...]
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Linking fresh and durability properties of paste to SCC mortar
H. Figueiras, S. Nunes, J. Coutinho, C. Andrade

Cement and Concrete Research (2014). Vol. 45, pp. 209-226

Abstract
In the last years many approaches to design SCC have been developed, but it remains a very complex process since it is necessary to manipulate several variables and understand their effects on concrete behaviour (fresh and hardened state). The prediction of concrete or mortar behaviour based on paste properties will be a significant contribution to simplify SCC design. With this purpose, two statistical experimental designs were carried out, one at paste level and the other at mortar level, to mathematically model the influence of mixture parameters on fresh and durability properties. The derived numerical models were used to define an area, labelled by self-compacting zone at paste level (SCZ), where fresh properties of the paste enable the design of SCC mortar. Furthermore, in order to extend this link to durability properties, the effect of including aggregate in cement paste was evaluated by means of the electrical resistivity test.
Abstract
In the last years many approaches to design SCC have been developed, but it remains a very complex process since it is necessary to manipulate several variables and understand [...]
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El Eurocódigo 2 y la evaluación de estructuras de hormigón armado con armaduras corroídas
J. Rodríguez, C. Andrade, D. Izquierdo, P. Tanner

Hormigón y Acero (2014). Vol. 65 (272), pp. 123-132

Abstract
The reinforcement corrosion is one of the major problems with relevant economic impact in the life cycle of concrete structures and that is why it is necessary to optimize the repair strategies in corroded structures. However, almost no international codes are available for structural evaluation and some criteria will be included in the revision of Eurocode 2 to evaluate existing deteriorated structures. A summary of Contecvet project funded EC is presented in this paper as well as some more recent developments. A first step in the evaluation of existing structures is to identify if the aggressive has reached the reinforcement and how much has affected to the structural performance. As soon as the corrosion rate has been calculated from the data taken in the structure, it is possible to estimate the rate of the structural deterioration process through the developed models and the remaining service life. Some models and expressions are summarized to estimate the residual bearing capacity of concrete structures with corroded reinforcement to be considered when drafting the new Eurocode 2.
Abstract
The reinforcement corrosion is one of the major problems with relevant economic impact in the life cycle of concrete structures and that is why it is necessary to optimize [...]
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Propuesta de modificación de los criterios de durabilidad del hormigón en el Eurocódigo 2
C. Andrade, R. Martínez, M. Sanjuán

Hormigón y Acero (2014). Vol. 65 (272), pp. 133-140

Abstract
The CEN/TC 250/SC2 and TC104/SC1 Committees have established a Joint Working Group, JWG TC250/TC104, in order to review all the durability aspects related to durability in Eurocode 2 “concrete structures” and EN 206-1 “concrete” standard. This JWG has studied the possibility of classifying concrete, not only by mechanical strength, but also by durability. This JWG has proposed that this classification be based on a direct test of carbonation or chloride resistance, which would oblige to make these types of tests routine in the future. As an alternative, the Spanish Mirror group has proposed to make this classification first by concrete mix proportioning as it is currently made and, in order to advance to a performance-based approach, by an indirect test (Durability Indicator). In present paper, the Spanish proposal is described and compared to that presented in the JWG. Advantages and disadvantages of both proposals are discussed and two Tables are presented that summarize what has been submitted by the AENOR CTN-140/SC2 for the revision of Chapter 4 of the Eurocode 2
Abstract
The CEN/TC 250/SC2 and TC104/SC1 Committees have established a Joint Working Group, JWG TC250/TC104, in order to review all the durability aspects related to durability in [...]
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Modelling the concrete‐real environment interaction to predict service life
C. Andrade

Structural Concrete (2015). Vol. 16 (2), pp. 1-2
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Recent durability studies on concrete structure
S. Tang, Y. Yao, C. Andrade, Z. Li

Cement and Concrete Research (2015). Vol. 78 (Part A), pp. 143-154

Abstract
The durability of concrete has attracted significant attention over the past several decades and is still a research hotspot until now. This paper reviews and discusses recent research activities on the durability of concrete, including: 1) major durability problems such as alkali aggregate reaction, sulfate attack, steel corrosion and freeze–thaw; 2) durability of concrete in marine environment; and 3) coupling effects of mechanical load and environmental factors on durability of concrete. Moreover, the consideration of durability in concrete structure design (DuraCrete and performance-based specifications) is also briefly reviewed.
Abstract
The durability of concrete has attracted significant attention over the past several decades and is still a research hotspot until now. This paper reviews and discusses [...]
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Multiple linear regression model for the assessment of bond strength in corroded and non-corroded steel bars in structural concrete
M. Prieto, P. Tanner, C. Andrade

Materials and Structures (2016). Vol. 49, pp. 4749-4763

Abstract
With the growth and ageing of the stock of existing structures, structural assessment and retrofitting are fast acquiring a significant role in the construction industry. The benefits of upgrading existing reinforced concrete (RC) structures or extending their service life and of ensuring greater durability in designs for de novo construction have led to a need to include deterioration as a factor in structural safety models. Bond between reinforcing steel and concrete is of cardinal importance in this respect. The present paper proposes a unified formulation for assessing bond strength in corroded and non-corroded steel bars, and an associated model to accommodate the effect of transverse pressure where appropriate. The formulation is the result of applying multiple linear regression analysis to a database built from the findings of over 650 bond tests on corroded and non-corroded reinforcing steel reported in the literature. The data collected include a wide range of variables affecting bond strength, such as bar diameter, concrete compressive strength, concrete cover, anchorage length, confinement ratio and cross-sectional loss. A number of statistical criteria are used to compare the proposed formulation to the other bond strength assessment models, including the fib Model Code 2010 proposal for corroded steel bars. Further to the statistical tests conducted, the model proposed can be usefully applied to assess the structural safety of corroded RC members.
Abstract
With the growth and ageing of the stock of existing structures, structural assessment and retrofitting are fast acquiring a significant role in the construction industry. [...]
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Estimating corrosion attack in reinforced concrete by means of crack opening
C. Andrade, A. Cesetti, G. Mancini, F. Tondolo

Structural Concrete (2016). Vol. 17 (4), pp. 533-540

Abstract
The corrosion of reinforcement in concrete is the most common degradation phenomenon of reinforced concrete structures. Reinforced concrete elements subjected to corrosion generally crack due to the expansive nature of oxides. One very important task is estimating the corrosion level using a non‐destructive method in order to establish both the actual safety of the structure and a priority intervention plan. Many researchers have studied the relationship between the corrosion phenomenon and the corresponding crack openings and their evolution; several statistical analyses, based on test data from experimental campaigns under a wide range of test conditions, are available. The present work attempts to contribute to finding a relationship between the crack opening and the amount of corrosion induced in the reinforcing bars. The result of the analysis is that only a reduced number of tests can be used to establish an empirical model based on a reliable set of test data. A simple relationship between crack opening and corrosion penetration is not recommended, due to the different parameters that are able to influence this correlation. Therefore, two fundamental parameters, the ratio of the concrete cover to the rebar diameter and the concrete strength, have also been considered. The considerations made regarding these parameter test results have been rearranged and the result is a formulation that shows reduced scatter
Abstract
The corrosion of reinforcement in concrete is the most common degradation phenomenon of reinforced concrete structures. Reinforced concrete elements subjected to corrosion [...]
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Indicator of carbonation front in concrete as substitute to phenolphthalein
S. Chinchón-Payá, C. Andrade, S. Chinchón-Yepes

Cement and Concrete Research (2016). Vol. 82, pp. 87-91

Abstract
A method to substitute the recognized toxic phenolphthalein in mortars and concretes is proposed. It comprises putting a portland cement sample in contact with an innocuous solution, curcumin-based, which acts as an indicator yielding a red color in areas where there is alkaline reserve (pH ~ 12) and yellow in carbonate zones (pH ≤ 9). Solutions containing curcumin extracted from commercial turmeric powder and from the rhizomes of the turmeric plant were prepared by using ethanol as a solvent. Subsequently it has been experienced with solutions in which curcumin has been used with a purity of over 95%. The dissolution of curcumin can be used with the same reliability as phenolphthalein in the carbonation process with the advantage that it is safe and presents no health risks.
Abstract
A method to substitute the recognized toxic phenolphthalein in mortars and concretes is proposed. It comprises putting a portland cement sample in contact with an innocuous [...]
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Review of the Current State of Knowledge on the Effects of Radiation on Concrete
T. Rosseel, I. Maruyama, Y. Pape, O. Kontani, A. Giorla, I. Remec, J. Wall, M. Sircar, C. Andrade, M. Ordoñez

Journal of Advanced Concrete Technology (2016). Vol. 14 (7), pp. 368-383

Abstract
A review of the current state of knowledge on the effects of radiation on concrete in nuclear power production applications is presented. Emphasis is placed on the effects of radiation damage, as reflected by changes in engineering properties of concrete, in the evaluation of the long-term operation and for plant life or aging management of nuclear power plants (NPPs) in Japan, Spain, and the United States. National issues and concerns are described for Japan and the United States followed by a discussion of the fundamental understanding of the effects of radiation on concrete. Specifically, the effects of temperature, moisture content, and irradiation on ordinary Portland cement paste and the role of temperature and neutron energy spectra on radiation-induced volumetric expansion (RIVE) of aggregate-forming minerals are described. This is followed by a discussion of the bounding conditions for extended operation; the significance of accelerated irradiation conditions; the role of temperature and creep; and how these issues are being incorporated into numerical and meso-scale models. From these insights on radiation damage, analyses of these effects on concrete structures are reviewed, and the current status of work in Japan and the United States is described. Also discussed is the recent formation of a new international scientific and technical organization, the International Committee on Irradiated Concrete, to provide a forum for timely information exchanges among organizations pursuing the identification, quantification, and modeling of the effects of radiation on concrete in commercial nuclear applications. The paper concludes with a discussion of research gaps, including (1) interpreting test-reactor data, (2) evaluating service-irradiated concrete for aging management and to inform radiation damage models with the Zorita NPP (Spain) serving as the first comprehensive test case, (3) irradiated-assisted alkali-silica reactions, and (4) RIVE under constrained conditions.
Abstract
A review of the current state of knowledge on the effects of radiation on concrete in nuclear power production applications is presented. Emphasis is placed on the effects [...]
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Substantial global carbon uptake by cement carbonation
F. Xi, S. Davis, P. Ciais, D. Crawford-Brown, D. Guan, C. Pade, T. Shi, M. Syddall, J. Lv, L. Ji, L. Bing, J. Wang, . Wei, K. Yang, B. Lagerblad, I. Galan, C. Andrade, Y. Zhang, Z. Liu

Nature Geoscience (2016). Vol. 9, pp. 880-883

Abstract
Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions from all industrial process and fossil-fuel combustion in 20131,2. Considerable attention has been paid to quantifying these industrial process emissions from cement production2,3, but the natural reversal of the process—carbonation—has received little attention in carbon cycle studies. Here, we use new and existing data on cement materials during cement service life, demolition, and secondary use of concrete waste to estimate regional and global CO2 uptake between 1930 and 2013 using an analytical model describing carbonation chemistry. We find that carbonation of cement materials over their life cycle represents a large and growing net sink of CO2, increasing from 0.10 GtC yr−1 in 1998 to 0.25 GtC yr−1 in 2013. In total, we estimate that a cumulative amount of 4.5 GtC has been sequestered in carbonating cement materials from 1930 to 2013, offsetting 43% of the CO2 emissions from production of cement over the same period, not including emissions associated with fossil use during cement production. We conclude that carbonation of cement products represents a substantial carbon sink that is not currently considered in emissions inventories.
Abstract
Calcination of carbonate rocks during the manufacture of cement produced 5% of global CO2 emissions from all industrial process and fossil-fuel combustion in 20131,2. [...]
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Corrosion induced cracking: Effect of different corrosion rates on crack width evolution
F. Pedrosa, C. Andrade

Construction and Building Materials (2017). Vol. 133, pp. 525-533

Abstract
Reinforcement corrosion leads to several damage types that influence the structure service lifetime, among which can be mentioned the cracking of concrete cover due to the increase in volume of the oxides with respect to the original volume of the parent steel. The relation between crack width and corrosion level has been studied by some authors while its analytical or numerical modelling is attracting increasing interest. In the modelling attempts, it has not been found the consideration of the corrosion rate effect, which, on the other hand was experimentally demonstrated more than 20 years ago. In the present paper the impact of different corrosion rates on the crack width development of reinforced concrete (RC) was studied. Identical RC prisms were subjected to accelerated corrosion in galvanostatic conditions with distinct electrical currents each, in order to monitor the superficial crack width growth of every specimen. Crack width growth with steel attack penetration is analysed as a two stage bilinear process where the crack width grows faster in the first stage. An empirical relation is found between the ratio crack width/steel attack and the corrosion rate applied for the first stage of cracking. With the new-found relation, a formula relating crack width evolution through time with the corrosion rate is presented. This study shows that it is crucial to take into account the strong influence of the corrosion rate on the crack width/steel attack ratio variation in order to successfully predict corrosion induced cracking
Abstract
Reinforcement corrosion leads to several damage types that influence the structure service lifetime, among which can be mentioned the cracking of concrete cover due to the [...]
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Contactless safety evaluation of damaged structures through energetic criteria
L. Saucedo-Mora, C. Andrade, C. López, J. Sánchez, A. Zamora

Structural Control and Health Monitoring (2017). Vol. 25 (1), pp. 1-11

Abstract
The reinforced concrete structures need to be monitored to ensure their structural integrity, but sometimes those measurements are very local, and the instrument is complex to locate physically in the structure and may interfere on it. Digital Image Correlation is a noncontact and nondestructive experimental technique capable to measure the displacement field in a big region of a structure with a great accuracy. This allows extracting valuable information from the fracture processes of reinforced concrete structures, critical for the evaluation of the structural integrity. The measurement of the energy dissipated by the structure is essential for the identification of the strength mechanisms that are failing in the structure and to identify a proper repair. Also, using fracture mechanics, other valuable information are extracted from the fracture processes of the reinforced concrete beam, such as the Modes I and II fracture energy released at each loading step, which is essential to evaluate the elastic energy that the structure can accumulate before collapse. The examples enable to anticipate the importance of Digital Image Correlation for future large scale studies of fracture in concrete and other materials related to construction.
Abstract
The reinforced concrete structures need to be monitored to ensure their structural integrity, but sometimes those measurements are very local, and the instrument is complex [...]
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Corrosion-induced brittle failure in reinforcing steel
J. Sánchez, J. Fullea, C. Andrade

Theoretical and Applied Fracture Mechanics (2017). Vol. 92, pp. 229-232

Abstract
Steel rebar corrosion is the main cause of reinforced concrete structure deterioration and shortened service life. A number of corrosion mechanisms induce geometric flaws in rebar, reducing its mechanical strength. Interstitial hydrogen, which lowers steel toughness, may also prompt embrittlement.This paper discusses the effect of local, pitting and corrosion stress on steel rebar performance. The findings show that rebar bearing strength depends on corrosion morphology and weight loss, which would explain the scatter in experimental results when the latter is the sole parameter studied.
Abstract
Steel rebar corrosion is the main cause of reinforced concrete structure deterioration and shortened service life. A number of corrosion mechanisms induce geometric flaws [...]
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The effect of two types of modified Mg-Al hydrotalcites on reinforcement corrosion in cement mortar
Z. Yang, R. Polder, J. Col, C. Andrade

Cement and Concrete Research (2017). Vol. 100, pp. 186-202

Abstract
Two modified Mg-Al hydrotalcites (MHTs), (MHT-pAB and MHT-NO2) were incorporated into mortar (with different w/c ratios) in two different ways: (1) as one of the mixing components in bulk mortar; (2) as part of cement paste coating of the reinforcing steel. Accelerated chloride migration, cyclic wetting-drying and diffusion tests were performed to investigate their effect on reinforcement corrosion. The results indicated that MHTs could be promising alternatives for preventing chloride-induced corrosion when an appropriate dosage is adopted and applied in a proper way, particularly, replacing 5% mass of cement by MHT-pAB in bulk mortar or as a coating of reinforcing steel (MHT-pAB/MHT-NO2 to replace 20% mass of cement). The effect of MHT-pAB on time-to-corrosion initiation (TTC) of reinforcing steel was estimated using the DuraCrete model. It was found that the incorporation of 5% MHT-pAB in bulk mortar led to a more than double TTC relative to reference mortar without MHTs.
Abstract
Two modified Mg-Al hydrotalcites (MHTs), (MHT-pAB and MHT-NO2) were incorporated into mortar (with different w/c ratios) in two different ways: (1) as one of the [...]
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Reliability analysis of corrosion onset: initiation limit state
C. Andrade

Journal of Structural Integrity and Maintenance (2017). Vol. 2 (4), pp. 200-208

Abstract
The relatively premature failure of structures by steel corrosion has increased interest in incorporating to the standards calculation of the time to corrosion. These models in general identify the end of service life with the starting of bar corrosion, either by chlorides or by carbonation. Additionally, from the publications of the project Duracrete, funded by the EU, probabilistic treatments have been applied to steel depassivation which is associated with a serviceability limit state (SLS). Thus, fib Model Code (MC2010) recommends a probability of failure of 10% for calculation of the time to corrosion. However, this recommendation leads to uncertainties because, on the one hand, the chloride threshold is not a fixed value and the carbonation front affects first the external face of the bar, developing progressive perimetral damage and, on the other hand, the consideration of the limit state as an SLS, with so low a fixed failure probability, introduces some degree of contradiction with the classical definition of the SLS. This is because, while the SLS is defined as a failure to fulfil the design prescriptions, any structural design performance changes just at the moment of steel depassivation. Additionally, no treatment on how to consider the damaged section or corrosion propagation model is usually given in the MC2010 or other standard and how to verify the classical SLS and ultimate limit state (ULS) is undefined. The present work introduces new perspectives on the subject from a probabilistic point of view by, (1) treating statistically the depassivation step, (2) by introducing a corrosion propagation model and quantifying the corrosion limit states and (3) by calculation of the depassivation probability which is dependent on the rate of the deterioration process itself. The whole exercise stresses the need to not consider a fixed value (10%) associated with a SLS as the probability of corrosion, but to consider it a limit state of “corrosion initiation” following ISO 2394. The value of the adequate probability of corrosion would be dependent on the consequences of the failure and on the rates of chloride ingress, of carbonation or of steel corrosion.
Abstract
The relatively premature failure of structures by steel corrosion has increased interest in incorporating to the standards calculation of the time to corrosion. These models [...]
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Fracto-surface mobility mechanism in high-strength steel wires
J. Sánchez, J. Fullea, C. Andrade

Engineering Fracture Mechanics (2017). Vol. 186, pp. 410-422

Abstract
Stress corrosion cracking, a mechanism governing steel deterioration, has yet to be fully understood. This article introduces a supplement to the surface mobility mechanism proposed by Galvele to include fracture mechanics principles. In the model proposed, anodic dissolution is regarded as the source of vacancies that would be driven by a stress gradient to the crack tip under non-stationary conditions. Denominated the fracto-surface mobility mechanism (FSMM), it explains material mechanical failure based on vacancy diffusion across the metal surface.
Abstract
Stress corrosion cracking, a mechanism governing steel deterioration, has yet to be fully understood. This article introduces a supplement to the surface mobility mechanism [...]
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Design and evaluation of service life through concrete electrical resistivity
C. Andrade

ALCONPAT (2018). Vol. 8 (3), pp. 264-279

Abstract
This paper describes the use of concrete electrical resistivity as durability performance parameter and the complementary information that resistivity can provide like: setting period, mechanical strength and degree of curing. Also, it is explained how to design the concrete mix to obtain a target resistivity. Current codes have prescriptive requirements for the durability of concrete and reinforcement corrosion. However, modern trends specify the performance rather than the concrete characteristics. This performance approach demands to define a durability controlling parameter, such as the chloride diffusion coefficient, with its corresponding test and the model to predict the time to steel corrosion.
Abstract
This paper describes the use of concrete electrical resistivity as durability performance parameter and the complementary information that resistivity can provide like: setting [...]
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Brief historical notes
C. Andrade

ALCONPAT (2018). Vol. 8 (3), pp. I-V

Abstract
Anniversaries are a good excuse to make some summaries of historical events. Very briefly, some advances made from the initial research in the speciality of reinforcement corrosion which started in the 60’s are summarized. The use of electrochemical techniques was a milestone which enabled, from the decade of the 1970, to study the effect of each variable with much more rigour. The studies on service life started in the decade of 1980, although they were not of general interest until the next decade. From 1990 RILEM Committees and the Iberoamerican Program on Corrosion of CYTED extended the knowledge so widely that in the XXI century the subject attracts much research interest.
Abstract
Anniversaries are a good excuse to make some summaries of historical events. Very briefly, some advances made from the initial research in the speciality of reinforcement [...]
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Apparent diffusion coefficient of oxygen and corrosion control of reinforcement rebar coated with primers
E. Pazini, C. Andrade

ALCONPAT (2018). Vol. 8 (3), pp. 288-301

Abstract
The present work evaluates the influence of five different types of coatings applied on the rebar on apparent diffusion coefficient of oxygen (Dap (O2)) and on the corrosion intensity (Icorr) in comparison with a reference coating composed of a cement-sand mortar. Oxygen flow (J (O2)) until the rebar was measured by potenciostático method in the steady state and the corrosion intensity (Icorr) was monitored by the Polarization Resistance technique (Rp). Evaluations for porosity of coatings were made through magnifying glasses, optical microscopy and SEM. The primers that represent barrier protection systems were, under the conditions tested, less permeable to oxygen. The apparent diffusion coefficient values (Dap (O2)) ranged from 2.1 x 10-6 cm2/s to 4 x 10-9 cm2/s, causing variations in the corrosion intensity measurements (Icorr), due to the cathodic corrosion process control.
Abstract
The present work evaluates the influence of five different types of coatings applied on the rebar on apparent diffusion coefficient of oxygen (Dap (O2)) and on the corrosion [...]
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Corrigendum to “Threshold concentration of chlorides in concrete for stainless steel reinforcement: Classic austenitic and new duplex stainless steel”
A. Panchón-Montaño, J. Sánchez, C. Andrade, J. Fullea, E. Moreno, V. Matres

Construction and Building Materials (2018). Vol. 189, p. 1303

Abstract
The authors regret that Equation 1: 30%w Ni not is correct. Should be changed to 30%w N, so that is; PREn = %w Cr + 3.3%w Mo + 30%w N-%w Mn. Footnote in Fig. 5 is not correct. Should be changed to “Micrographs (4×) of EN 1.4362/2304 duplex rebar; left: after removal from specimen; right: after pickling (4×)”. The authors would like to apologise for any inconvenience caused
Abstract
The authors regret that Equation 1: 30%w Ni not is correct. Should be changed to 30%w N, so that is; PREn = %w Cr + 3.3%w Mo + 30%w N-%w Mn. Footnote in [...]
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Threshold concentration of chlorides in concrete for stainless steel reinforcement: Classic austenitic and new duplex stainless steel
A. Panchón-Montaño, J. Sánchez, C. Andrade, J. Fullea, E. Moreno, V. Matres

Construction and Building Materials (2018). Vol. 186, pp. 495-502

Abstract
Stainless steel rebars is used to lengthen the service life of structures in aggressive media. Corrosion resistance was studied in five grades of mortar-embedded stainless steel: EN 1.4307, EN 1.4404, EN 1.4482, EN 1.4362 and EN 1.4462. A modified accelerated chloride attack was applied to prevent steel rebar polarisation and artificial re-passivation. The critical chloride concentration was determined. Based on corrosion rate, service life was calculated for a given exposure at two probability levels.
Abstract
Stainless steel rebars is used to lengthen the service life of structures in aggressive media. Corrosion resistance was studied in five grades of mortar-embedded stainless [...]
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Updating Carbon Storage Capacity of Spanish Cements

C. Andrade, M. Sanjuán

Sustainability (2018). Vol. 10 (12), pp. 1-15

Abstract
The fabrication of cement clinker releases CO2 due to the calcination of the limestone used as raw material, which contributes to the greenhouse effect. The industry is involved in a process of reducing this amount liberated to the atmosphere by mainly lowering the amount of clinker in the cements. The cement-based materials, such as concrete and mortars, combine part of this CO2 by a process called “carbonation”. Carbonation has been studied lately mainly due to the fact that it induces the corrosion of steel reinforcement when bringing the CO2 front to the surface of the reinforcing bars. Thus, the “rate of carbonation” of the concrete cover is characterized by and linked to the length of service life of concrete structures. The studies on how much CO2 is fixed by the hydrated phases are scarce and even less has been studied the influence of the type of cement. In present work, 15 cements were used to fabricate paste and concrete specimens withwater/cement (w/c) ratios of 0.6 and 0.45 which reproduce typical concretes for buildings and infrastructures. The amount of carbon dioxide uptake was measured through thermal gravimetry. The degree of carbonation, (DoC) is defined as the CO2 fixed with respect to the total theoretical maximum and the carbon storage capacity (CSC) as the carbonation uptake by a concrete element, a family or the whole inventory of a region or country. The results in the pastes where analyzed with respect to the uptake by concretes and indicated that: (a) the humidity of the pores is a critical parameter that favours the carbonation reaction as higher is the humidity (within the normal atmospheric values), (b) all types of cement uptake CO2 in function of the CaO of the clinker except the binders having slags, which can uptake additional CO2 giving aDoC near or above 100%. The CSC of Spain has been updated with respect to a previous publication resulting in proportions of 10.8–11.2% of the calcination emissions, through considering a ratio of “surface exposed/volume of the element” of 3 as an average of the whole Spanish asset of building and infrastructures.
Abstract
The fabrication of cement clinker releases CO2 due to the calcination of the limestone used as raw mater