Failure Mechanism of RC Structure under Reversed Cyclic Loading after Flexural Yielding

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"Reversed cyclic loading failure" was proposed on the basis of cyclic loading tests of RC beams in the previous study. Under reversed cyclic loading, a shear-resisting mechanism in a plastic-hinging region repeats temporary disappearance and rebuilding. In order to maintain the strength under reversed cyclic loading, it is necessary to satisfy the following two conditions : Condition 1. The shear-resisting mechanism which has temporarily disappeared is rebuilt. Condition 2. The rebuilt shear-resisting mechanism is not destroyed by shear load. Shear failure occurs when the condition 2 is not satisfied. On the other hand, "Reversed cyclic loading failure" occurs when the condition 1 is not satisfied.Reversed cyclic loading tests of RC column was carried out. In the experiment, the deformation behavior of plastic-hinging region and buckling behavior of longitudinal bar was observed in detail. On the basis of the results, the failure process was investigated and the following conclusions were obtained.The observed failure mechanism of RC column under reversed cyclin loading was similar to that of "Reversed cyclic loading failure". Under reversed cyclin loading, a resisting mechanism repeats temporary disappearance and rebuilding in the same manner as beam under reversed cyclin loading. And the strength deterioration occurs when the condition 1 is not satisfied.