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• Combination of 3D solid finite elements with rotation-free beam elements for non-linear analysis of fiber reinforced polymer rebars

  F. Zarate, T. Villette, X. Martinez, F. Rastellini Canela, D. Cendón, C. Andrade, E. Oñate

  Rev. int. métodos numér. cálc. diseño ing. (2023). Vol. 39, (2), 12

  
  

  Abstract

  We present a combination of three dimensional (3D) solid elements and rotation-free beam elements for non-linear analysis of fiber-reinforced polymer (FRP) of rebars. The matrix material is modelled by 3D solid elements while the fibers are modelled with rotation-free beam elements. The absence of rotation variables in the beam elements allows the straightforward coupling of 3D solid and beam elements using a formulation with displacement nodal degrees of freedom only. Both solid and beam elements are formulated in an updated Lagrangian description. The behavior of the matrix and the fiber material are modelled with an elastic-damage model. The efficiency and accuracy of the combined 3D-beam element formulation are verified in examples of application to the analysis of FRP rebars up to fracture in axial, bending and shear tests for which experimental results are available.

  Abstract
  We present a combination of three dimensional (3D) solid elements and rotation-free beam elements for non-linear analysis of fiber-reinforced polymer (FRP) of rebars. The [...]

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• A Lagrangian–Eulerian procedure for the coupled solution of the Navier–Stokes and shallow water equations for landslide-generated waves

  M. Maso, A. Franci, I. de-Pouplana, A. Cornejo Velázquez, E. Oñate

  Advanced Modeling and Simulation in Engineering Sciences (2022). Vol. 9(1), Article 15, 2022

  
  

  Abstract

  This work presents a partitioned method for landslide-generated wave events. The proposed strategy combines a Lagrangian Navier Stokes multi-fluid solver with an Eulerian method based on the Boussinesq shallow water equations. The Lagrangian solver uses the Particle Finite Element Method to model the landslide runout, its impact against the water body and the consequent wave generation. The results of this fully-resolved analysis are stored at selected interfaces and then used as input for the shallow water solver to model the far-field wave propagation. This one-way coupling scheme reduces drastically the computational cost of the analyses while maintaining high accuracy in reproducing the key phenomena of the cascading natural hazard. Several numerical examples are presented to show the accuracy and robustness of the proposed coupling strategy and its applicability to large-scale landslide-generated wave events. The validation of the partitioned method is performed versus available results of other numerical methods, analytical solutions and experimental measures.

  Abstract
  This work presents a partitioned method for landslide-generated wave events. The proposed strategy combines a Lagrangian Navier Stokes multi-fluid solver with an Eulerian [...]

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• A unified non-linear energy dissipation-based plastic-damage model for cyclic loading

  A. Cornejo Velázquez, S. Jiménez, L. Barbu, S. Oller, E. Oñate

  Computer Methods in Applied Mechanics and Engineering (2022). Vol. 400,115543

  
  

  Abstract

  A new energy-dissipation-based rate-independent constitutive law within the framework of elastoplasticity coupled with damage is proposed. With this methodology, the inelastic strains and the stiffness degradation exhibited by quasi-brittle materials under monotonic or cyclic loading conditions are taken into account. The proposed constitutive model is able to capture micro-cracks closure-reopening effects due to load reversal. A wide variety of hardening/softening laws on the stress–strain relationship are described and considered for the novel normalized plastic-damage energy dissipation internal variable. This normalized internal variable allows the model to be independent on the sign of the load and dissipate different fracture energies (tensile, compressive and potentially shear) in a natural way. Several numerical examples are presented in order to ensure the efficiency and validity of the proposed model for simulating the non-linear behaviour of quasi-brittle materials under monotonic and cyclic loading. Some numerical aspects of the implemented algorithm and the return mapping procedure are also described in detail and discussed.

  Abstract
  A new energy-dissipation-based rate-independent constitutive law within the framework of elastoplasticity coupled with damage is proposed. With this methodology, the inelastic [...]

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• Explicit time integration scheme with large time steps for first order transient problems using finite increment calculus (preprint)

  E. Oñate, I. de-Pouplana, F. Zarate

  Computer Methods in Applied Mechanics and Engineering (2022). Available online 14 July, 115332

  
  

  Abstract

  We present an explicit integration scheme for solving the transient heat conduction equation that allows larger time steps than the standard forward Euler scheme. The derivation starts from a higher order form of the governing differential equations of the problem obtained using a Finite Increment Calculus (FIC) procedure. The efficiency of the new explicit integration scheme in terms of substantial gains in the time step size versus the forward Euler scheme is verified in the solution of transient heat conduction problems in one and two dimensions. The method is readily extendible to other problems in mechanics governed by the first order transient differential equation.

  Abstract
  We present an explicit integration scheme for solving the transient heat conduction equation that allows larger time steps than the standard forward Euler scheme. The derivation [...]

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• Structural analysis and design of a large inflatable hangar for aircrafts (preprint)

  J. Gonzalez, J. Marcipar, C. Estruch, E. Oñate

  Structural Engineering International (2022). pp. 1-5

  
  

  Abstract

  Buildair S.A. has recently designed, manufactured and built an inflatable hangar (termed H75 hangar) for the aeronautic industry in Jeddah Airport (Kingdom of Saudi Arabia). H75 hangar is the largest aircell inflated structure ever built in the world, finally erected in July 2019. The structural analysis and design of the main body of the hangar has involved complex structural concepts due to the specificity of the structural elements employed, like membranes and straps which lead to a highly non-linear mechanical problem, or the treatment of wind over the structure without a defined standard for inflatable structures. In this paper, the structural conception and specificities of the structure are presented, as well as the design procedure for the H75 hangar based in the numerical analysis, to fulfill the design requirements in terms of stresses, and deformations for the structural elements of the main body.

  Abstract
  Buildair S.A. has recently designed, manufactured and built an inflatable hangar (termed H75 hangar) for the aeronautic industry in Jeddah Airport (Kingdom of Saudi Arabia). [...]

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• Synergistic effects of tubular halloysite clay and zirconium phosphate on thermal behavior of intumescent coating for structural steel

  Y. Lee, F. Ahmad, S. Kabir, P. Masset, E. Oñate, G. Yeoh

  Journal of Materials Research and Technology (2022). Vol. 18, pp. 4456-4469

  
  

  Abstract

  Zirconium phosphate (ZrP) recently introduced in intumescent fire protective coating has shown improvement in developing ceramic layer. The tubular halloysite clay (THC) due to its unique molecular structure can be combined with ZrP to enhance fire resistance by developing a strong silica network on the char surface. This study is aimed to investigate the synergistic effects of tubular halloysite clay and zirconium phosphate fillers to improve the thermal performance of the intumescent coating. The control coating formulation and a range of coating formulations using a combination of weight percentage of THC and ZrP were developed to study the influences of fillers on fire performance. The char expansion and fire resistance tests of the coatings were conducted using furnace fire test and Lab scale fire jet. Thermal stability of the coating was determined by TGA and char was characterized by FESEM, XRD, FTIR and XPS. Water-resistance test of the coating was performed according to ASTM D-870. Results showed that the reinforcement of THC-ZrP showed promising improvement on the performance of IFC and substrate temperature was far below the critical temperature, 550 °C. Sample HZ 5 showed the least backside steel substrate temperature of 219 °C. Expansion rate of char was found reduced with the addition of THC but improved the char compactness. The addition of THC and ZrP in IFC improved 18% fire resistance performance and 5% residual wt. Of char. Char morphology showed silica network, XRD and FTIR confirmed the presence of silicon. Water absorption test showed 95% less water absorption (HZ-5) compared to control coating. Post water immersion, fire test showed 7% increase in substrate temperature which is 18% less than control coating after water immersion fire test.

  Abstract
  Zirconium phosphate (ZrP) recently introduced in intumescent fire protective coating has shown improvement in developing ceramic layer. The tubular halloysite clay (THC) [...]

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• Adaptive breakwaters with inflatable elements for coastal protection. Preliminary numerical estimation of their performance

  P. Ryzhakov, F. Hermosilla, P. Ubach, E. Oñate

  Ocean Engineering (2022). Volume 251, 110818

  
  

  Abstract

  Excessive erosion of sand beaches defines a serious problem worldwide and is particularly pronounced in the Mediterranean region. One of the typical measures for alleviating this erosion consists in building rigid breakwaters in the vicinity of the coast for diminishing sand transport. This solution, however, is often accompanied by undesirable alteration of the coastline. In this work we address the viability of using conceptually new structures with inflatable elements striving to improve the control over the sediment transport. The aim of the inflatable element is to adapt the breakwater configuration to the sea state. A preliminary design is proposed and tested in a number of storm scenarios using an in-house finite element/level set model. Influence of various breakwater design parameters upon its functionality is studied. Transmission coefficients and maximum pressures exerted upon the breakwater are estimated. Numerical study performed shows that for the considered range of storm scenarios the proposed design is characterized by transmission coefficients below 0.5. It is also shown that the use of inflatable elements facilitates adaptation of the breakwater functionality to a given sea state.

  Abstract
  Excessive erosion of sand beaches defines a serious problem worldwide and is particularly pronounced in the Mediterranean region. One of the typical measures for alleviating [...]

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• Numerical simulation of particle impact drilling (PID) systems: a one-way coupled approach

  G. Casas, I. de-Pouplana, R. Gandikota, E. Oñate

  Computational Particle Mechanics (2022). pp. 1-23

  
  

  Abstract

  A numerical technique based on a CFD-DEM method is presented for the analysis of particle impact drilling (PID) systems. The method is built from a preexisting finite element Navier–Stokes solver for the fluid phase and a discrete element method module for the steel particles which this drilling technology utilizes to enhance the penetration rate. We provide a detailed description of the most relevant implementation issues, including our choice of the hydrodynamic forces appropriate for power-law fluids. We also discuss several critical aspects related to the validity of the simplifying assumptions that will be helpful to simulation engineers. We apply our simple, one-way coupled approach on designs provided by an industrial partner to illustrate its potential as an analysis tool for this promising drilling technology. The goal of this work is, on the one hand, to provide evidence for the usefulness of the numerical approach as a design tool for PID systems, as well as a detailed discussion of the different aspects to be assessed for an effective simulation campaign. On the other hand, a series of modeling aspects that require further work are identified. The focus of the simulation campaign presented is on the particles and fluid flow characteristics within the drill bit.

  Abstract
  A numerical technique based on a CFD-DEM method is presented for the analysis of particle impact drilling (PID) systems. The method is built from a preexisting finite element [...]

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• A FIC-FEM procedure for the shallow water equations over partially wet domains

  M. Maso, I. de-Pouplana, E. Oñate

  Computer Methods in Applied Mechanics and Engineering (2022). Volume 389, 114362

  
  

  Abstract

  We present a stable finite element formulation for the shallow water equations using the finite increment calculus (FIC) procedure. This research is focused on the stability properties of the FIC technique and uses linear triangles for the spatial discretization with an equal order of interpolation for all the variables. The extension to higher order polynomial interpolation functions and different geometries is straightforward. The present FIC-FEM procedure is also able to introduce artificial viscosity for an adequate shock capturing. An implicit time integration has been used. Special attention has been payed to the dry domain in order to solve the moving boundaries with a fixed mesh Eulerian approach. Three academic examples are included in order to test the capabilities of the FIC-FEM procedure: the global stabilization, the shock capturing technique and the dry-wet interface. An experimental benchmark tests the overall accuracy of the present formulation.

  Abstract
  We present a stable finite element formulation for the shallow water equations using the finite increment calculus (FIC) procedure. This research is focused on the stability [...]

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• Combination of the finite element method and particle-based methods for predicting the failure of reinforced concrete structures under extreme water forces

  E. Oñate, A. Cornejo Velázquez, F. Zarate, K. Kashiyama, A. Franci

  Engineering Structures (2022). Vol. 251, Part B, 113510

  
  

  Abstract

  We present a combination of the Finite Element Method (FEM), the Particle Finite Element Method (PFEM), and the Discrete Element Method (DEM) for modeling and analyzing the failure of reinforced concrete structures under impulsive wave forces originating from free-surface flows in critical water hazards. The free-surface water flow is modeled with the PFEM, while the structural behavior and the fractures induced by the water forces in the structure are modeled with a coupled FEM–DEM technique. The concrete material behavior is simulated with a standard isotropic damage model. The reinforcing bars are modeled by a rule of mixtures procedure, for simplicity. The possibilities of the new integrated PDFEM approach for predicting the evolution of free-surface tsunami-type waves and their devastating effect on constructions are validated with experiments on the failure of reinforced concrete plates under large impacting waves, performed in a laboratory facility in Japan.

  Abstract
  We present a combination of the Finite Element Method (FEM), the Particle Finite Element Method (PFEM), and the Discrete Element Method (DEM) for modeling and analyzing the [...]

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