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

“反向循环荷载破坏”是在前人对钢筋混凝土梁进行循环荷载试验的基础上提出的。在反向循环荷载作用下，塑性铰区的抗剪机制反复出现暂时性消失和重建。为了在反向循环荷载下保持强度，需要满足以下两个条件：条件1。重建了暂时消失的抗剪机构。条件2。重建后的抗剪机构不受剪切荷载破坏。当条件2不满足时，发生剪切破坏。另一方面，当条件1不满足时，发生“反向循环加载失效”。对钢筋混凝土柱进行了反循环加载试验。在试验中，对塑性铰区的变形行为和纵筋的屈曲行为进行了详细的观察。在此基础上，对其破坏过程进行了研究，得出了以下结论：观察到的钢筋混凝土柱在反循环荷载作用下的破坏机制与“反循环荷载破坏”相似。在反周期蛋白作用下，抵抗机制与梁在反周期蛋白作用下一样，反复出现暂时消失和重建的过程。当条件1不满足时，发生强度劣化。

"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.