Serviceability of reinforced concrete beams under high-cycle fatigue loading

摘要

Serviceability requirements of concrete structures often deal with control of crack widths anddeflections. It is well known that such variables increase with number of cycles, but the currentlyavailable models assume some simplifications to include this cyclic increase. The estimation isusually made by affecting the monotonic response of the element by long term factors. Althoughthis methodology usually yields conservative results, it does not actually account for the realisticcyclic behaviour of reinforced concrete in tension and may be unsafe under the permanent loadlevel. In the paper, the progressive degradation of the bond properties in the tension chord withnumber of cycles is included in a cycle-dependent model. In addition, the fatigue damage ofconcrete in the compression zone is accounted for. The paper presents how both degradationmechanisms of the tension and compression zones are coupled. The proposed model allows theestimation of crack widths and deflections of flexurally loaded elements under cyclic loads. Themodel results are compared in the paper with experiments on cyclically loaded reinforced concretebeams. The study allows understanding the different interaction played by the degradationmechanisms in lightly and heavily reinforced concrete beams.