Experimental and parametric study on critical compressive strain of concrete under creep effect

Abstract

This thesis mainly dealt with the effect of creep on the critical compressive strain (CCS) of concrete. The strain of concrete corresponding to peak compressive stress is crucially important in selecting the ultimate yield strength of reinforcing bar as used in reinforced concrete. Among various influencing factors such as creep, shrinkage, loading rate and confinement, effect of creep and shrinkage is quite significant. Until recently, it has not been studied how these factors may affect CCS of concrete. Therefore, to investigate the effect of creep and shrinkage on CCS, experimental and parametric study is conducted as presented in this thesis. Creep and loading-rate-effect experiments were performed to study their effect on the CCS of concrete. In parameter study, age-adjusted effective modulus method was adopted considering various parameters by covering almost all the possible range as adopted in practice. Based on this study, empirical equations of predicting CCS of concrete and the corresponding ultimate yield strength of bar used in reinforced concrete are formulated as a function of loading level, steel ratio, ultimate creep coefficient and ultimate drying shrinkage over time.