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• Modeling material failure in concrete structures under cyclic actions

  R. Faria, M. Cervera, J. Oliver

  Journal of Structural Engineering (2004). 130 (12), pp. 1997-2005.

  
  

  Abstract

  A constitutive model devised for the analysis of concrete structures, and suitable for generic two- or three-dimensional applications, is presented and validated. For plain concrete a tension-compression distinguishing stress split is performed, and two scalar damage variables account for the degradation induced by the tensile and compressive stress components. As outcomes the model reproduces the stiffness recovery upon load reversal, and it captures the strength enhancement under multiaxial compression. Besides, the simple formulation as well as the extremely reduced number of parameters involved in the concrete model makes it quite suitable for the analysis of real structures, and constitutes a useful design tool. As regards to the nonlinear performance of the steel reinforcement, the explicit Giuffrè–Menegotto–Pinto model is adopted. Efficiency of the global model is illustrated via two seismic applications: one concerning an arch dam, and the other a six-floor reinforced concrete wall. The latter application is presented for validation purposes.

  Abstract
  A constitutive model devised for the analysis of concrete structures, and suitable for generic two- or three-dimensional applications, is presented and validated. For plain [...]

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• Vulnerabilidad sísmica de hospitales. Fundamentos para ingenieros y arquitectos

  O. Cardona

  Monograph Series in Earthquake Engineering, editor A. H. Barbat (1999). MIS32, ISBN: 84-89925-33-X

  
  

  Abstract

  El propósito de esta monografía es informar a las personas involucradas en la planeación, operación, manejo y diseño de servicios de salud a cerca de los efectos que pueden sufrir los hospitales por la ocurrencia de movimientos sísmicos, con el fin de suministrar una herramienta útil que les permita incorporar los procedimientos de mitigación del riesgo, tanto en la inspección de las instalaciones existentes como en el diseño y construcción de nuevas edificaciones y servicios. El documento trata temas específicos relacionados con los problemas potenciales que se pueden generar en el caso de la ocurrencia de un sísmo e, igualmente, hace referencia a las medidas que se deben tomar para la mitigación, haciendo especial énfasis en los requisitos necesarios para que las instalaciones puedan mantener su función durante e inmediatamente después de un evento intenso. No obstante que las instalaciones de la salud pueden ser afectadas por un amplio espectro de fenómenos naturales como sismos, huracanes, deslizamientos, erupciones  volcánicas, inundaciones, etc., o de origen antrópico, como incendios, explosiones, escapes de gas, entre otros, este documento hace énfasis en el problema sísmico, dado que es el fenómeno natural que más ha afectado las instalaciones de la salud y debido a que si se logra reducir sus efectos directos e indirectos, prácticamente se está reduciendo el riesgo que pueden causar otros fenómenos, cuya acción es normalmente menos que la de los sismos.

  Abstract
  El propósito de esta monografía es informar a las personas involucradas en la planeación, operación, manejo y diseño de servicios de salud [...]

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• A stabilized formulation for incompressible plasticity using linear triangles and tetrahedra

  M. Chiumenti, Q. Valverde, C. Agelet de Saracibar, M. Cervera

  International Journal of Plasticity (2004). 20 (8-9), pp. 1487-1504

  
  

  Abstract

  In this paper, a stabilized finite element method to deal with incompressibility in solid mechanics is presented. Both elastic and J2-plastic constitutive behavior have been considered. A mixed formulation involving pressure and displacement fields is used and a continuous linear interpolation is considered for both fields. To circumvent the Babuška–Brezzi condition a stabilization technique based on the orthogonal sub-scale method is introduced. The main advantage of the method is the possibility of using linear triangular or tetrahedral finite elements, which are easy to generate for real industrial applications. Results are compared with standard Galerkin and Q1P0 mixed formulations in either elastic or elasto-plastic incompressible problems.

  Abstract
  In this paper, a stabilized finite element method to deal with incompressibility in solid mechanics is presented. Both elastic and J2-plastic constitutive behavior have been [...]

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• Softening, localization and stabilization: capture of discontinuous solutions in J2 plasticity

  M. Cervera, M. Chiumenti, C. Agelet de Saracibar

  Int. J. Numer. Anal. Meth. Geomech. (2004). 28 (5), pp. 373-393.

  
  

  Abstract

  This paper exploits the concept of stabilization techniques to improve the behaviour of mixed linear/linear simplicial elements (triangles and tetrahedra) in incompressible or nearly incompressible situations. Elasto‐J2‐plastic constitutive behaviour has been considered with linear and exponential softening. Two different stabilization methods are used to attain global stability of the corresponding discrete finite element formulation. Implementation and computational aspects are also discussed, showing that a robust application of the proposed formulation is feasible. Numerical examples show that the formulation derived is free of volumetric locking and spurious oscillations of the pressure. The results obtained do not suffer from spurious mesh‐size or mesh‐bias dependence, comparing very favourably with those obtained with the standard, non‐stabilized, approaches.

  Abstract
  This paper exploits the concept of stabilization techniques to improve the behaviour of mixed linear/linear simplicial elements (triangles and tetrahedra) in incompressible [...]

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• Avaliação do comportamento sísmico de barragens de betão

  R. Faria

  Monograph Series in Earthquake Engineering, editor A. H. Barbat (1998). MIS31, ISBN: 84-89925-28-3

  
  

  Abstract

  This monograph is devoted to the numerical evaluation of the seismic performance of concrete dams, with a particular emphasis on arch typology, here represented by the portuguese Alto Lindoso and Foz Côa dams. Koyna gravity dam, located in Indica, is also studied.

  Abstract
  This monograph is devoted to the numerical evaluation of the seismic performance of concrete dams, with a particular emphasis on arch typology, here represented by the portuguese [...]

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• Numerical modelling of concrete curing, regarding hydration and temperature phenomena

  M. Cervera, R. Faria, T. Prato, J. Oliver

  Computers and Structures (2002). Vol. 80 (18–19), pp. 1511-1521

  
  

  Abstract

  A numerical model that accounts for the hydration and aging phenomena during the early ages of concrete curing is presented in a format suitable for a finite element implementation. Assuming the percolation of water through the hydrates already formed as the dominant mechanism of cement hydration, the model adopts an internal variable called hydration degree, whose evolution law is easily calibrated and allows an accurate prediction of the hydration heat production. Compressive strength evolution is related to the aging degree, a concept that accounts for the influences of the hydration and curing temperature on the final mechanical properties of concrete. The model capabilities are illustrated by means of a wide set of experimental tests involving ordinary and high performance concretes, and through the simulation of the concrete curing on a viaduct deck of the Öresund Link.

  Abstract
  A numerical model that accounts for the hydration and aging phenomena during the early ages of concrete curing is presented in a format suitable for a finite element implementation. [...]

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• Acciones para el diseño sísmico de estructuras

  R. Aguiar

  Monograph Series in Earthquake Engineering, editor A. H. Barbat (1998). MIS30, ISBN: 84-89925-27-5

  
  

  Abstract

  Se presenta la metodología de cálculo para evaluar la peligrosidad sísmica a nivel regional orientada al diseño sísmico de estructuras. Las diferentes etapas de evaluación se describen en forma crítica con la presentación de resultados encontrados en diferentes zonas del mundo.

  Abstract
  Se presenta la metodología de cálculo para evaluar la peligrosidad sísmica a nivel regional orientada al diseño sísmico de estructuras. [...]

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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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• 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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