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Formulation and Verification of a Concrete Model with Strong Coupling between Isotropic Damage and Elastoplasticity and Comparison to a Weak Coupling Model

Title
Formulation and Verification of a Concrete Model with Strong Coupling between Isotropic Damage and Elastoplasticity and Comparison to a Weak Coupling Model
Author
George Voyiadjis
Keywords
Nonlinear finite element analysis (FEA); Fracture energy based continuum damage mechanics; Elastic-plastic-damage coupling; Concrete material model
Issue Date
2012-05
Publisher
ASCE AMERICAN SOCIETY OF CIVIL ENGINEERS
Citation
JOURNAL OF ENGINEERING MECHANICS, Vol.138, No.5 [2012], p530-p541
Abstract
In this work, a new concrete model that strongly couples continuum-damage-mechanics to elastoplasticity is presented. The model incorporates a plasticity yield criterion written in terms of the nominal/damaged, rather than effective, stress space. Tensile and compressive behaviors are modeled through the damage-affected-multi-hardening nature of the plasticity yield criterion and the introduction of two (tensile and compressive) plasticity-affected isotropic damage initiation/growth criteria, where plasticity variables are added to the definition of the tensile and compressive growth functions of damage. A nonassociative plastic flow rule is used to control inelastic dilatancy. Specific expressions of the elastic/damage and plastic/damage components of the Helmholtz free energy function are presented. The constitutive equations of the model are consistently derived within a sound framework of irreversible thermodynamics. These free energy expressions are used to define three plasticity and damage interconnected dissipation mechanisms, one plasticity mechanism and two damage mechanisms. The elastic-plastic-damage, elastic-plastic, and elastic-damage tangent operators are also derived. A computational algorithm for the numerical integration of the constitutive equations is proposed on the basis of the doubly passive predictor-plastic-damage corrector approach. The model is implemented in the Finite Element (FE) analysis software ABAQUS through a user defined material subroutine (UMAT). Two- and three-dimensional verification examples are carried out to demonstrate the effectiveness and robustness of the proposed model in producing results that depict experimentally observed concrete behaviors. The results of the proposed model are compared with those of a weak coupling concrete model recently presented by the authors, in which damage was incorporated in the elastic formulation whereas plasticity remained in the effective stress space. The comparison shows the effect of strong-coupling on increasing/accelerating the degradation of concrete when the same material parameters of the weak coupling model are used. The results of the proposed model are also compared with those of well known strong-coupling models available in contemporary literature. To reduce the sensitivity of the nonlinear FE analysis of concrete structures to the refinement of the FE meshes, the damage density parameters are defined to include embedded dimensionless coefficients that are related to concrete's fracture energies (in tension and compression) and to the geometrical characteristic length provided by ABAQUS software during the analysis. The conclusions drawn from this work clearly indicate the adequacy of the model to describe the different stages of concrete behavior and stiffness and strength degradations attributable to elastoplasticity-affected damage growth. They also show that the model can be further improved and equipped with nonlocal measures to enhance its future performance. DOI: 10.1061/(ASCE)EM.1943-7889.0000344.
URI
https://ascelibrary.org/doi/10.1061/%28ASCE%29EM.1943-7889.0000344http://hdl.handle.net/20.500.11754/66972
ISSN
0733-9399
DOI
10.1061/(ASCE)EM.1943-7889.0000344
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > CIVIL AND ENVIRONMENTAL ENGINEERING(건설환경공학과) > Articles
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