Effect of strain rate on post-peak cyclic behavior of concrete in direct tension

A test method has been developed to obtain reliable post-peak cyclic behavior of concrete in this study. Considering three various loading regimes, strain rate effect on post-peak stress-strain response of concrete is investigated. The envelope curve is found coincides with the monotonic loading curve, which is shown to govern the cyclic response. Concrete presents slightly rate sensitive when it is subjected to static loading. The tensile strength increases with the increasing of strain rate. The stress releases with cyclic even if the maximum strain is constant. It demonstrated that the stress release process is independent of strain rate and it can be expressed by a power function. Analytical expressions introducing damage index are proposed to describe the entire monotonic behavior, as well the response to cyclic loadings. The analytical model uses the concept of uniqueness of envelope curve. The calculated results predicted by the analytical expressions have good agreement with test data.