Plastic-Damage Models And User-Defined Material Subroutine In ABAQUS Software Of Concrete

Elastic-plastic damage models have many advantages in modeling broken and unstabilization of concrete material and structures, so using elastic-plastic damage models to research high dams, nuclear power station, highway and military works have been a pop spot of solid mechanics. Based on the elastic-plastic damage model of ref[1], three aspects about the problem of elastic-plastic damage analysis for concrete materials and structures were done.(1) The forming of this elastic-plastic damage models which has the character of triaxiality dependent hardening has been studied in the frame of continuum mechanics ,and the discrete formation of the constitutive eqution for this elastic-plastic damage model has also been proposed.(2) Studies on parameter identification of a plasticity-based damage constitutive model for concrete are presented in this section. Differences between the stress-strain curves experimentally obtained and the ones numerically obtained at local level were used as the objective function of a regularized least square method. For solving the inverse problem, the solution of the direct problem at local level obtained by a driver subroutine was embedded in the iterative solution procedure for the inverse problem proposed in this paper. The sensitivity matrix was calculated numerically by the finite difference method. Numerical examples are given for fitting the numerically obtained stress-strain curves to a set of experimental results. Parameter identifications under uniaxial compression were performed. The values of parameters obtained by inverse analysis were used to simulate numerically the stress-strain behaviors under various loading cases, which include uniaxial extension and triaxial compression with different confining stresses. Results indicate that the numerical scheme is stable and has reasonable accuracy(3) With FORTRAN language, the UMAT was developed on the basis of ABAQUS plat form. With this UMAT,which was based on the constitutive eqution of this paper, ABAQUS can calculate Cauchy stress, plastic strain, damage. Numerical results of field variations obtained with the new implemented model have been exported to the ODB file which is the storage file of numerical results prepared for postprocess via UVARM subroutine. many loading cases of one-element cubic block and 216-elemet numerical tests have been carried out with the UMAT subtoutine. Numerical results indicate that the UMAT subroutine developed here has improved the ability of Abaqus software in simulating the plastic damage behaviour of concrete.