The Experts below are selected from a list of 10323 Experts worldwide ranked by ideXlab platform
Javier Oliver - One of the best experts on this subject based on the ideXlab platform.
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Mesoscopic model to simulate the mechanical behavior of reinforced concrete members affected by corrosion
International Journal of Solids and Structures, 2010Co-Authors: Pablo J. Sánchez, Javier Oliver, Alfredo Edmundo Huespe, Sebastian ToroAbstract:Abstract In this contribution, a finite element methodology devised to simulate the structural deterioration of corroded reinforced concrete members is presented. The proposed numerical strategy has the ability to reproduce many of the well-known (undesirable) mechanical effects induced by corrosion processes in the embedded steel bars, as for example: expansion of the reinforcements due to the corrosion product accumulation, damage and cracking patterns distribution in the surrounding concrete, degradation of steel–concrete bond stress transfer, net area reduction in the reinforcements and, mainly, the influence of all these mentioned mechanisms on the structural load carrying capacity predictions. At the numerical level, each component of the RC structure is represented by means of a suitable FE formulation. For the concrete, a cohesive model based on the Continuum Strong Discontinuity Approach (CSDA) is used. Steel bars are modeled by means of an elasto-plastic constitutive relation. The interface is simulated using contact-friction elements, with the friction degradation as a function of the degree of corrosion attack. Two different (and coupled) mesoscopic analyzes are considered in order to describe the main physical phenomena that govern the problem: (i) an analysis at the cross section level and (ii) an analysis at the structural member level. The resultant mechanical model can be used to simulate generalized reinforcement corrosion. Experimental and previous numerical results, obtained from the available literature, are used to validate the proposed strategy.
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Numerical modelling of the fracture process in reinforced concrete by means of a continuum Strong Discontinuity approach. Part II: application to shear panels
Universidad Nacional de Colombia, 2010Co-Authors: Dorian Luís Linero Segrera, Javier Oliver, Alfredo Edmundo HuespeAbstract:The numerical simulation results of the fracture process in reinforced concrete shear panels are presented in this work. The simulation used a model based on the continuum Strong Discontinuity approach (CSDA) and mixing theory. CSDA describes strain localization and formation of Discontinuity associated with the appearance of a crack. On the other hand, mixing theory represents composite material behaviour which is formed by a simple concrete matrix and one or two bundles of long reinforcement bars. The behaviour of simple concrete and steel is represented by a two-dimensional damage model and one-dimensional plasticity model, respectively. The model has been implemented in the finite element method which considers plane stress, infinitesimal strain and static loads. Three panels are simulated, reinforced in one or two ways;they are mainly subjected to shear forces. The numerical simulation results as well as structural response and cracking patterns were satisfactory
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two dimensional modeling of material failure in reinforced concrete by means of a continuum Strong Discontinuity approach
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: Javier Oliver, Alfredo Edmundo Huespe, Dorian L Linero, Osvaldo L ManzoliAbstract:Abstract The paper presents a new methodology to model material failure, in two-dimensional reinforced concrete members, using the Continuum Strong Discontinuity Approach (CSDA). The mixture theory is used as the methodological approach to model reinforced concrete as a composite material, constituted by a plain concrete matrix reinforced with two embedded orthogonal long fiber bundles (rebars). Matrix failure is modeled on the basis of a continuum damage model, equipped with strain softening, whereas the rebars effects are modeled by means of phenomenological constitutive models devised to reproduce the axial non-linear behavior, as well as the bond–slip and dowel effects. The proposed methodology extends the fundamental ingredients of the standard Strong Discontinuity Approach, and the embedded Discontinuity finite element formulations, in homogeneous materials, to matrix/fiber composite materials, as reinforced concrete. The specific aspects of the material failure modeling for those composites are also addressed. A number of available experimental tests are reproduced in order to illustrate the feasibility of the proposed methodology.
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continuum approach to material failure in Strong Discontinuity settings
Computer Methods in Applied Mechanics and Engineering, 2004Co-Authors: Javier Oliver, Alfredo Edmundo HuespeAbstract:The paper focuses the numerical modelling of material failure in a Strong Discontinuity setting using a continuum format. Displacement discontinuities, like fractures, cracks, slip lines, etc., are modelled in a Strong Discontinuity approach, enriched by a transition from weak to Strong discontinuities to get an appropriate representation of the fracture process zone. The introduction of the Strong Discontinuity kinematics automatically projects any standard dissipative constitutive model, equipped with strain softening, into a discrete traction–separation law that is fulfilled at the Discontinuity interface. Numerical issues like a global Discontinuity tracking algorithm via a heat conduction-like problem are also presented. Some representative numerical simulations illustrate the performance of the presented approach.
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continuum approach to the numerical simulation of material failure in concrete
International Journal for Numerical and Analytical Methods in Geomechanics, 2004Co-Authors: Javier Oliver, Alfredo Edmundo Huespe, Esteban Samaniego, Eduardo W V ChavesAbstract:SUMMARY Some new aspects of the continuum Strong Discontinuity approach (CSDA) to model material failure in geomaterials are addressed. A new global algorithm, for tracking multiple crack lines/surfaces in 2D/3D cases is proposed. It is based on solving a simple heat conduction-like problem accompanying the standard mechanical algorithm. A viscous perturbation method on the crack surface is also proposed to remedy the instabilities caused by mutual interactions of multiple developing cracks. A simple procedure to compute the critical time step that ensures algorithmic uniqueness is then provided. Numerical simulations of twoand three-dimensional problems displaying a multi-crack pattern are finally presented. Copyright # 2004 John Wiley & Sons, Ltd.
Alfredo Edmundo Huespe - One of the best experts on this subject based on the ideXlab platform.
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Mesoscopic model to simulate the mechanical behavior of reinforced concrete members affected by corrosion
International Journal of Solids and Structures, 2010Co-Authors: Pablo J. Sánchez, Javier Oliver, Alfredo Edmundo Huespe, Sebastian ToroAbstract:Abstract In this contribution, a finite element methodology devised to simulate the structural deterioration of corroded reinforced concrete members is presented. The proposed numerical strategy has the ability to reproduce many of the well-known (undesirable) mechanical effects induced by corrosion processes in the embedded steel bars, as for example: expansion of the reinforcements due to the corrosion product accumulation, damage and cracking patterns distribution in the surrounding concrete, degradation of steel–concrete bond stress transfer, net area reduction in the reinforcements and, mainly, the influence of all these mentioned mechanisms on the structural load carrying capacity predictions. At the numerical level, each component of the RC structure is represented by means of a suitable FE formulation. For the concrete, a cohesive model based on the Continuum Strong Discontinuity Approach (CSDA) is used. Steel bars are modeled by means of an elasto-plastic constitutive relation. The interface is simulated using contact-friction elements, with the friction degradation as a function of the degree of corrosion attack. Two different (and coupled) mesoscopic analyzes are considered in order to describe the main physical phenomena that govern the problem: (i) an analysis at the cross section level and (ii) an analysis at the structural member level. The resultant mechanical model can be used to simulate generalized reinforcement corrosion. Experimental and previous numerical results, obtained from the available literature, are used to validate the proposed strategy.
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Numerical modelling of the fracture process in reinforced concrete by means of a continuum Strong Discontinuity approach. Part II: application to shear panels
Universidad Nacional de Colombia, 2010Co-Authors: Dorian Luís Linero Segrera, Javier Oliver, Alfredo Edmundo HuespeAbstract:The numerical simulation results of the fracture process in reinforced concrete shear panels are presented in this work. The simulation used a model based on the continuum Strong Discontinuity approach (CSDA) and mixing theory. CSDA describes strain localization and formation of Discontinuity associated with the appearance of a crack. On the other hand, mixing theory represents composite material behaviour which is formed by a simple concrete matrix and one or two bundles of long reinforcement bars. The behaviour of simple concrete and steel is represented by a two-dimensional damage model and one-dimensional plasticity model, respectively. The model has been implemented in the finite element method which considers plane stress, infinitesimal strain and static loads. Three panels are simulated, reinforced in one or two ways;they are mainly subjected to shear forces. The numerical simulation results as well as structural response and cracking patterns were satisfactory
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vulnerability analysis of large concrete dams using the continuum Strong Discontinuity approach and neural networks
Structural Safety, 2008Co-Authors: Manolis Papadrakakis, J. Oliver, Vissarion Papadopoulos, Alfredo Edmundo Huespe, Nikos D. Lagaros, Pablo J. SánchezAbstract:Abstract Probabilistic analysis is an emerging field of structural engineering which is very significant in structures of great importance like dams, nuclear reactors etc. In this work a Neural Networks (NN) based Monte Carlo Simulation (MCS) procedure is proposed for the vulnerability analysis of large concrete dams, in conjunction with a non-linear finite element analysis for the prediction of the bearing capacity of the Dam using the Continuum Strong Discontinuity Approach. The use of NN was motivated by the approximate concepts inherent in vulnerability analysis and the time consuming repeated analyses required for MCS. The Rprop algorithm is implemented for training the NN utilizing available information generated from selected non-linear analyses. The trained NN is then used in the context of a MCS procedure to compute the peak load of the structure due to different sets of basic random variables leading to close prediction of the probability of failure. This way it is made possible to obtain rigorous estimates of the probability of failure and the fragility curves for the Scalere (Italy) dam for various predefined damage levels and various flood scenarios. The uncertain properties (modeled as random variables) considered, for both test examples, are the Young’s modulus, the Poisson’s ratio, the tensile strength and the specific fracture energy of the concrete.
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two dimensional modeling of material failure in reinforced concrete by means of a continuum Strong Discontinuity approach
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: Javier Oliver, Alfredo Edmundo Huespe, Dorian L Linero, Osvaldo L ManzoliAbstract:Abstract The paper presents a new methodology to model material failure, in two-dimensional reinforced concrete members, using the Continuum Strong Discontinuity Approach (CSDA). The mixture theory is used as the methodological approach to model reinforced concrete as a composite material, constituted by a plain concrete matrix reinforced with two embedded orthogonal long fiber bundles (rebars). Matrix failure is modeled on the basis of a continuum damage model, equipped with strain softening, whereas the rebars effects are modeled by means of phenomenological constitutive models devised to reproduce the axial non-linear behavior, as well as the bond–slip and dowel effects. The proposed methodology extends the fundamental ingredients of the standard Strong Discontinuity Approach, and the embedded Discontinuity finite element formulations, in homogeneous materials, to matrix/fiber composite materials, as reinforced concrete. The specific aspects of the material failure modeling for those composites are also addressed. A number of available experimental tests are reproduced in order to illustrate the feasibility of the proposed methodology.
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continuum approach to material failure in Strong Discontinuity settings
Computer Methods in Applied Mechanics and Engineering, 2004Co-Authors: Javier Oliver, Alfredo Edmundo HuespeAbstract:The paper focuses the numerical modelling of material failure in a Strong Discontinuity setting using a continuum format. Displacement discontinuities, like fractures, cracks, slip lines, etc., are modelled in a Strong Discontinuity approach, enriched by a transition from weak to Strong discontinuities to get an appropriate representation of the fracture process zone. The introduction of the Strong Discontinuity kinematics automatically projects any standard dissipative constitutive model, equipped with strain softening, into a discrete traction–separation law that is fulfilled at the Discontinuity interface. Numerical issues like a global Discontinuity tracking algorithm via a heat conduction-like problem are also presented. Some representative numerical simulations illustrate the performance of the presented approach.
Osvaldo L Manzoli - One of the best experts on this subject based on the ideXlab platform.
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modeling of interfaces in two dimensional problems using solid finite elements with high aspect ratio
Computers & Structures, 2012Co-Authors: Osvaldo L Manzoli, Andre Luis Gamino, Eduardo A Rodrigues, G K S ClaroAbstract:Highlights? Modeling thin interface with solid finite elements with very high aspect ratio. ? A scalar damage model can be used to describe bond degradation due to slip. ? The technique can model the bond-slip behavior of rebars embedded in concrete. ? Densification of the finite elements in the interface region is not required. ? Discrete constitutive relations and contact elements are not necessary. The use of standard solid finite elements with a very high aspect ratio is proposed to model the behavior of thin interface regions between distinct components of composite structural members. It is shown that these elements present the same kinematics as the Continuous Strong Discontinuity Approach (CSDA) and can be used to describe bond stresses between components, even when the thickness of the interface region tends to zero. A scalar damage model consistent with the CSDA is presented to describe bond degradation due to slip. The technique is successfully applied to model the bond-slip behavior of reinforcing bars embedded in concrete.
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two dimensional modeling of material failure in reinforced concrete by means of a continuum Strong Discontinuity approach
Computer Methods in Applied Mechanics and Engineering, 2008Co-Authors: Javier Oliver, Alfredo Edmundo Huespe, Dorian L Linero, Osvaldo L ManzoliAbstract:Abstract The paper presents a new methodology to model material failure, in two-dimensional reinforced concrete members, using the Continuum Strong Discontinuity Approach (CSDA). The mixture theory is used as the methodological approach to model reinforced concrete as a composite material, constituted by a plain concrete matrix reinforced with two embedded orthogonal long fiber bundles (rebars). Matrix failure is modeled on the basis of a continuum damage model, equipped with strain softening, whereas the rebars effects are modeled by means of phenomenological constitutive models devised to reproduce the axial non-linear behavior, as well as the bond–slip and dowel effects. The proposed methodology extends the fundamental ingredients of the standard Strong Discontinuity Approach, and the embedded Discontinuity finite element formulations, in homogeneous materials, to matrix/fiber composite materials, as reinforced concrete. The specific aspects of the material failure modeling for those composites are also addressed. A number of available experimental tests are reproduced in order to illustrate the feasibility of the proposed methodology.
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Strong discontinuities and continuum plasticity models the Strong Discontinuity approach
International Journal of Plasticity, 1999Co-Authors: Javier Oliver, Miguel Cervera, Osvaldo L ManzoliAbstract: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.
Yiming Zhang - One of the best experts on this subject based on the ideXlab platform.
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cracking elements method for dynamic brittle fracture
Theoretical and Applied Fracture Mechanics, 2019Co-Authors: Yiming Zhang, Xiaoying ZhuangAbstract:Abstract The cracking elements (CE) method is a recently presented self-propagating Strong Discontinuity embedded approach with the statically optimal symmetric (SDA-SOS) formulation for simulating the fracture of quasi-brittle materials. CE uses disconnected cracking segments to represent cracks, and the crack openings are condensed locally; hence, this method does not require remeshing, a cover algorithm or nodal enrichment. Furthermore, local criteria for determining the crack orientations are presented, thus making crack tracking unnecessary. In this paper, we propose a CE numerical procedure for dynamic fractures. Several benchmark tests regarding irregular discretizations are performed, and the results indicate that the CE method is capable of naturally capturing complicated crack patterns in dynamic fractures, including crack branchings.
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cracking elements a self propagating Strong Discontinuity embedded approach for quasi brittle fracture
Finite Elements in Analysis and Design, 2018Co-Authors: Xiaoying Zhuang, Yiming ZhangAbstract:Abstract In this paper, we present a self-propagating Strong Discontinuity embedded Approach (SDA) for quasi-brittle fracture. The method is based on the Statically Optimal Symmetric formulation (SOS) of the SDA using the 8-node quadrilateral element which avoids local stress locking. A non-continuous crack path is assumed such that the crack is modelled by a set of disconnected cracking segments. Hence, no complex crack tracking procedure and no explicit (or implicit) representation of the crack surface are needed. A local fracture criteria is proposed for determining the orientation of the crack. Several numerical tests with irregular discretizations are performed, demonstrating the effectiveness and robustness of the presented method.
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A softening-healing law for self-healing quasi-brittle materials: Analyzing with Strong Discontinuity embedded approach
Engineering Fracture Mechanics, 2018Co-Authors: Yiming Zhang, Xiaoying ZhuangAbstract:Quasi-brittle materials such as concrete suffer from cracks during their life cycle, requiring great cost for conventional maintenance or replacement. In the last decades, self-healing materials are developed which are capable of filling and healing the cracks and regaining part of the stiffness and strength automatically after getting damaged, bringing the possibility of maintenance-free materials and structures. In this paper, a time dependent softening-healing law for self-healing quasi-brittle materials is presented by introducing limited material parameters with clear physical background. Strong Discontinuity embedded Approach (SDA) is adopted for evaluating the reliability of the model. In the numerical studies, values of healing parameters are firstly obtained by back analysis of experimental results of self-healing beams. Then numerical models regarding concrete members and structures built with self-healing and non-healing materials are simulated and compared for showing the capability of the self-healing material.
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Strong Discontinuity embedded approach with standard sos formulation element formulation energy based crack tracking strategy and validations
Computer Methods in Applied Mechanics and Engineering, 2015Co-Authors: Yiming Zhang, Roman Lackner, Matthias Zeiml, Herbert A MangAbstract:Abstract The Strong Discontinuity embedded Approach (SDA) has proved to be a robust numerical method for simulating fracture of quasi-brittle materials such as glass and concrete. Three different numerical formulations are used in the SDA: (i) Statically Optimal Symmetric (SOS), (ii) Kinematically Optimal Symmetric (KOS), (iii) Statically and Kinematically Optimal Nonsymmetric (SKON). While the SOS formulation (standard version) of the SDA is simple for coding and provides good numerical stability (considering standard Galerkin method), several researchers have pointed out that this formulation encounters serious stress-locking. In this paper, an SOS formulation of the SDA is presented, considering elements with linear and quadratic interpolation for the displacement field. The performance of the proposed model of crack simulation is investigated by re-analysis of a pulling test, a three-point bending test, and an L-shaped panel with prescribed crack paths. The obtained results show that elements with linear interpolation encounter significant stress-locking, whereas elements with quadratic interpolation give good results without locking. Based on the eight-node quadrilateral element, which showed the best performance in the aforementioned re-analysis of the tests, an energy-based crack-tracking strategy, originally used in the framework of the XFEM, is modified and implemented into the SDA model. Several numerical benchmark tests, including an L-shaped panel test, a tension-shear test, a notched panel test, four-point bending tests with single and double notches, and a pull-out test are performed, illustrating the good performance with respected to the SDA model and the robustness of the proposed crack-tracking strategy.
Xiaoying Zhuang - One of the best experts on this subject based on the ideXlab platform.
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cracking elements method for dynamic brittle fracture
Theoretical and Applied Fracture Mechanics, 2019Co-Authors: Yiming Zhang, Xiaoying ZhuangAbstract:Abstract The cracking elements (CE) method is a recently presented self-propagating Strong Discontinuity embedded approach with the statically optimal symmetric (SDA-SOS) formulation for simulating the fracture of quasi-brittle materials. CE uses disconnected cracking segments to represent cracks, and the crack openings are condensed locally; hence, this method does not require remeshing, a cover algorithm or nodal enrichment. Furthermore, local criteria for determining the crack orientations are presented, thus making crack tracking unnecessary. In this paper, we propose a CE numerical procedure for dynamic fractures. Several benchmark tests regarding irregular discretizations are performed, and the results indicate that the CE method is capable of naturally capturing complicated crack patterns in dynamic fractures, including crack branchings.
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cracking elements a self propagating Strong Discontinuity embedded approach for quasi brittle fracture
Finite Elements in Analysis and Design, 2018Co-Authors: Xiaoying Zhuang, Yiming ZhangAbstract:Abstract In this paper, we present a self-propagating Strong Discontinuity embedded Approach (SDA) for quasi-brittle fracture. The method is based on the Statically Optimal Symmetric formulation (SOS) of the SDA using the 8-node quadrilateral element which avoids local stress locking. A non-continuous crack path is assumed such that the crack is modelled by a set of disconnected cracking segments. Hence, no complex crack tracking procedure and no explicit (or implicit) representation of the crack surface are needed. A local fracture criteria is proposed for determining the orientation of the crack. Several numerical tests with irregular discretizations are performed, demonstrating the effectiveness and robustness of the presented method.
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A softening-healing law for self-healing quasi-brittle materials: Analyzing with Strong Discontinuity embedded approach
Engineering Fracture Mechanics, 2018Co-Authors: Yiming Zhang, Xiaoying ZhuangAbstract:Quasi-brittle materials such as concrete suffer from cracks during their life cycle, requiring great cost for conventional maintenance or replacement. In the last decades, self-healing materials are developed which are capable of filling and healing the cracks and regaining part of the stiffness and strength automatically after getting damaged, bringing the possibility of maintenance-free materials and structures. In this paper, a time dependent softening-healing law for self-healing quasi-brittle materials is presented by introducing limited material parameters with clear physical background. Strong Discontinuity embedded Approach (SDA) is adopted for evaluating the reliability of the model. In the numerical studies, values of healing parameters are firstly obtained by back analysis of experimental results of self-healing beams. Then numerical models regarding concrete members and structures built with self-healing and non-healing materials are simulated and compared for showing the capability of the self-healing material.
