Long‐term deformations of concrete under cyclic‐mechanical and cyclic‐hygric exposures

Long‐term deformations of concrete structures are actually calculated by creep models using the mean stress level and the time‐average ambient humidity. However, temporally varying mechanical and hygric exposures which occur in practice are suspected to increase the time‐dependent strains. Nevertheless, these influences have not been sufficiently investigated so far.

Therefore, the influences of cyclic‐mechanical and ‐hygric loadings, respectively, as well as their coupled influence on the long‐term deformations of concrete are systematically investigated within the scope of a joint research project funded by the German Research Foundation (DFG). In this paper, time‐dependent strains due to cyclic‐mechanical and/or ‐hygric loading of a normal strength concrete are presented in comparison to those at corresponding constant loading.

The results demonstrate that the time‐dependent strains are significantly increased due to cyclic‐mechanical and ‐hygric loading compared to those due to the corresponding constant mean loading. This indicates an underestimation of strains by using the constant mean loading in creep models and may cause severe safety risks in prestressed concrete constructions. Therefore, existing models should be modified considering the influences of cyclic exposures.