COMPUATATIONAL ASPECTS OF MICROPLANE MODEL M4 FOR CONCRETE: DEFICIENCIES AND IMPROVEMENTS

摘要

This paper presents a comprehensive analysis on the numerical stability and robustness of the Microplane model M4 developed by Prof.Bazant and his coworkers, which is a sophisticated material model for concrete. Some important insufficiencies in the computational aspects of this model are discovered including: directional bias with the frequently used alternative for micro shear stress, dependence of model response on the strain increment magnitude, distinctly different model response with various integration schemes and significant loading direction dependence of the numerical results. These weaknesses must be eliminated in order to obtain reliable and accurate results in the nonlinear finite element calculation of reinforced concrete with this model. Some remedies are proposed in this paper though developing a novel numerical algorithm for the micro volumetric and deviatoric stresses and an enhanced integration scheme. The above deficiencies can be effectively removed with the new remedies.