Influence of moisture content on strain development of concrete subjected to compressive creep and cyclic loading

The expected long-term deformations of concrete structures today are calculated using creep models, assuming constant mechanical loads. Nevertheless, in many structures like bridges constant creep loads are superimposed with cyclic loads of substantial magnitude. The effect of such a cyclic loading onto the concrete deformation behaviour so far has been unkown. An underestimation of the resulting deformation by established creep models might cause serious damage and safety risks for the structure. Before this background, the strain development due to creep and cyclic loading of a normal strength concrete have been comparatively investigated at two different moisture contents (approx. 100 % and 75 %). The results show that viscous strains from cyclic loading are significantly higher than those from purely static loading despite identical mean stress levels. Further, the resulting strains are considerably affected by the moisture content of concrete. The gathered results provide the basis for improving existing creep models.