chapter  I
1 Pages

1 2J

D egradation o f concre te compressive s t r e n g th To include the plastic stiffness degradation effects in the pre-and post-failure regimes, the parameter x in Eqn (3) is derived as function of a history dependent plastic damage variable, effective viscoplastic strain, to fit quasi-static experimental results. Based on empirical rate sensitivity factors, this function is extended for dynamic problems. For the prefailure range, an isotropic hardening rule is developed which assumes the uniform expansion of the loading surface to be rate and history dependent. In Ref [1], the normalized effective stress is defined by the following hardening function