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Hajime Matsuoka - One of the best experts on this subject based on the ideXlab platform.

  • a unified constitutive model for both clay and sand with hardening parameter independent on stress path
    Computers and Geotechnics, 2008
    Co-Authors: Hajime Matsuoka
    Abstract:

    Abstract A unified constitutive model for both clay and sand under three-dimensional stress conditions is derived from the modified Cam-clay model, by taking the following two points into consideration. First, a transformed stress tensor based on the SMP (spatially mobilized plane) criterion is applied to the Cam-clay model. The proposed model consistently describes shear yielding and shear failure and combines critical state theory with the SMP criterion for clay. Secondly, a new hardening parameter, which is independent of the stress path, is derived in order to develop a unified constitutive model for both clay and sand. It not only describes the dilatancy for lightly to heavily dilatant sand, but also reduces to the Plastic Volumetric Strain for clay. The validity of the hardening parameter is confirmed by the test results of triaxial compression and extension tests on sand under various stress paths. Only five conventional soil parameters are needed in the proposed model.

  • SMP Criterion-Based Unified Constitutive Model for Geomaterials
    Soil Constitutive Models, 2005
    Co-Authors: Hajime Matsuoka, Yangping Yao, De’an Sun
    Abstract:

    A unified and simple constitutive model for both clay and sand under three-dimensional stress conditions is presented. The model was developed from the modified Cam-clay model, and the following two points are considered. First, a so-called transformed stress tensor based on the SMP criterion is applied to the modified Cam-clay model to improve the model capability in describing the behavior of soils in general stresses including triaxial compression. The transformed stress tensor is deduced from what we transform the SMP criterion to a circle in the transformed π-plane. The model realizes the consistency from the shear yield to the shear failure and the combination of the critical state theory with the SMP criterion. Secondly, a new hardening parameter is introduced in order to develop a unified constitutive model for both clay and sand. It can not only describe the dilatancy from lightly to heavily dilative sand, but also be reduced to the Plastic Volumetric Strain for normally consolidated clay. The results predicted by the presented model are compared in detail with the test results of sand and clay in triaxial compression, true triaxial, plane Strain and triaxial extension. It is shown that the presented model can describe well the drained and undrained behavior of clay and sand along various stress paths including triaxial compression, triaxial extension, plane Strain, and true triaxial conditions. Only five conventional soil parameters are needed in the model.

  • A Unified ElastoPlastic Model for Clay and Sand with the SMP Criterion
    1999
    Co-Authors: Yp Yao, Hajime Matsuoka, Da Sun
    Abstract:

    In this paper, the modified Cam-clay model is revised to a unified elastoPlastic model for clay and sand under three-dimensional stress conditions in the following two aspects. Firstly, the method for the transformation of the curved surface of the SMP (Spatially Mobilized Plane) criterion to a cone in the transformed principal stress space is proposed by introducing a transformed stress. The transformed stress is applied to the Cam-clay model. The revised model realizes the consistency from the shear yield to the shear failure and the combination of the Cam-clay model with the SMP criterion for clay. Secondly, in order to develop a unified constitutive model for clay and sand, a new hardening parameter is derived, which can not only describe the dilatancy of sand, but also be reduced to the Plastic Volumetric Strain for normally consolidated clay.

S Michelponnelle - One of the best experts on this subject based on the ideXlab platform.

  • a non local finite element based on Volumetric Strain gradient application to ductile fracture
    Computational Materials Science, 2009
    Co-Authors: R Bargellini, Jacques Besson, Eric Lorentz, S Michelponnelle
    Abstract:

    The aim of this work is to propose a finite element formulation adapted to ductile fracture simulation using Continuum Damage Mechanics and unravelling two main encountered difficulties. First, as ductile damage represents voids nucleation and growth, constitutive behaviors conStrain the Plastic Volumetric Strain through damage evolution laws, leading to Volumetric locking. A specific formulation is consequently needed. A three-field formulation is defined, in which volume change is treated as a new unknown; its relation to the displacement field is weakly enforced by mean of a Lagrange multiplier. Then, Strain and damage localisation occurs due to softening, and leads to spurious mesh dependent solutions. A coupling between neighbouring material points is thus introduced through a volume change gradient term added in the three field formulation. First results show that this formulation permits to control localisation and to unravel mesh dependency.

Vassilis K. Papanikolaou - One of the best experts on this subject based on the ideXlab platform.

  • three dimensional combined fracture Plastic material model for concrete
    International Journal of Plasticity, 2008
    Co-Authors: Jan Cervenka, Vassilis K. Papanikolaou
    Abstract:

    Abstract This paper describes a combined fracture–Plastic model for concrete. Tension is handled by a fracture model, based on the classical orthotropic smeared crack formulation and the crack band approach. It employs the Rankine failure criterion, exponential softening, and it can be used as a rotated or a fixed crack model. The Plasticity model for concrete in compression is based on the Menetrey–Willam failure surface, the Plastic Volumetric Strain as a hardening/softening parameter and a non-associated flow rule based on a nonlinear Plastic potential function. Both models use a return-mapping algorithm for the integration of constitutive equations. Special attention is given to the development of an algorithm for the combination of the two models. The suggested combination algorithm is based on a recursive substitution, and it allows for the two models to be developed and formulated separately. The algorithm can handle cases when failure surfaces of both models are active, but also when physical changes such as crack closure occur. The model can be used to simulate concrete cracking, crushing under high confinement and crack closure due to crushing in other material directions. The model is integrated in a general finite element package ATENA and its performance is evaluated by comparisons with various experimental results from the literature.

  • Confinement-sensitive Plasticity constitutive model for concrete in triaxial compression
    International Journal of Solids and Structures, 2007
    Co-Authors: Vassilis K. Papanikolaou, Andreas J. Kappos
    Abstract:

    Abstract In this paper, a confinement-sensitive Plasticity constitutive model for concrete in triaxial compression is presented, aiming to describe the strength and deformational behaviour of both normal and high-strength concrete under multiaxial compression. It incorporates a three-parameter loading surface, uncoupled hardening and softening functions following the accumulation of Plastic Volumetric Strain and a nonlinear Lode-angle dependent Plastic potential function. The various model parameters are calibrated mainly on the basis of a large experimental database and are expressed in terms of only the uniaxial compressive concrete strength, leading to a single-parameter model, suitable for practical applications. The model’s performance is evaluated against experimental results and it is found that both the increased strength and deformation capacity of confined concrete are properly captured.

R Bargellini - One of the best experts on this subject based on the ideXlab platform.

  • a non local finite element based on Volumetric Strain gradient application to ductile fracture
    Computational Materials Science, 2009
    Co-Authors: R Bargellini, Jacques Besson, Eric Lorentz, S Michelponnelle
    Abstract:

    The aim of this work is to propose a finite element formulation adapted to ductile fracture simulation using Continuum Damage Mechanics and unravelling two main encountered difficulties. First, as ductile damage represents voids nucleation and growth, constitutive behaviors conStrain the Plastic Volumetric Strain through damage evolution laws, leading to Volumetric locking. A specific formulation is consequently needed. A three-field formulation is defined, in which volume change is treated as a new unknown; its relation to the displacement field is weakly enforced by mean of a Lagrange multiplier. Then, Strain and damage localisation occurs due to softening, and leads to spurious mesh dependent solutions. A coupling between neighbouring material points is thus introduced through a volume change gradient term added in the three field formulation. First results show that this formulation permits to control localisation and to unravel mesh dependency.

Peter Grassl - One of the best experts on this subject based on the ideXlab platform.

  • Modelling of dilation of concrete and its effect in triaxial compression
    Finite Elements in Analysis and Design, 2003
    Co-Authors: Peter Grassl
    Abstract:

    This paper deals with the modelling of the dilation characteristics of concrete in compression. Triaxial stress states, which are usually activated by prevention of dilation, often govern the load resistance of concrete structures. Therefore, a realistic description of the dilation characteristics of concrete is important.The influence of the dilation characteristics of concrete on the behaviour of actively and passively confined structures was studied. A Plasticity approach proposed by Grassl et al. (Int. J. Solid Struct. 39 (2002) 5205) was used to study representative examples of concrete cylinders confined with steel and carbon fibre-reinforced polymers (CFRP). The Plasticity model used combines an isotropic hardening law, based on the Plastic Volumetric Strain as hardening parameter, with a non-associated flow rule and a yield surface based on a three-parameter failure criterion proposed by Menetrey and Willam (ACI Struct. J. 92 (1995) 311).It is shown that the Plasticity model proposed is capable of predicting the response of both steel- and CFRP-confined cylinders. In the case of steel-confined cylinders, the yield strength of the confining steel is reached so early that the dilation has only a small influence. However, the dilation characteristics of concrete have a strong influence on the axial stress-Strain response of the CFRP-confined cylinders.