Concrete creep under variable loadings

In this thesis, the long-term concrete behavior under time-varying loading histories was experimentally studied at material and structural level. The analysed loading histories consisted of sustained and variable repeated loads applied in alternating cycles of loading/unloading with different load pattern, namely: constant, stair-cased and arbitrarily distributed variable load. The selected test variables allowed understanding of the creep and the creep recovery under repeated stresses as well as identification of important aspects of the hardly predictable loading histories that govern the long-term response of concrete elements. The developed numerical procedure for prediction of long-term behavior taking into account the detailed loading history corresponded to the experimental campaign so that it worked at material as well as at structural level. Finally, based on the experimental and numerical results, recommendations were given about how to treat variable loads with respect to their creeping effects.