Hysteretic Fracturing Endochronic Theory for Concrete

Abstract

An improved endochronic nonlinear triaxial constitutive relation for concrete is developed: (1)In addition to plastic strain increments proportional to stress tensor, fracturing strain increments proportional to strain tensor are used to model strain-softening; (2)the plastic and fracturing inelastic strain increments are characterized by different intrinsic times; (3)degradation of the elastic shear modulus is determined by the intrinsic time for the fracturing strain increments, and degradation of the bulk modulus is related to that of the shear modulus using Budianski-O'Connell's expressions for the elastic moduli of randomly microcracked material; (4)jump-kinematic hardening, in which the center of the loading surface jumps into the current stress and strain point whenever loading reverses to unloading or vice versa, is introduced. The theory also exhibits hydrostatic pressure sensitivity, inelastic dilatancy, initial shear compaction in triaxial loading, and inelastic strain due to hydrostatic pressure.