Seismic Performance Evaluation of RC Hollow Piers under Level II Earthquake by Hybrid Loading Tests

本研究主要探讨混凝土空心桥墩的抗震性能。（1）从循环荷载试验结果来看，剪跨比对混凝土柱的破坏形态和变形能力有很大的影响。河谷地区桥梁的短墩通常由不同高度的桥墩组成，因此对短墩的变形性能进行校核是非常重要的。(b)在循环荷载作用下，钢筋混凝土空心墩的变形中有一个不可忽略的剪切分量. (c)混合地震加载试验结果表明，结构的滞回响应是稳定的，能够通过滞回作用耗散输入能量。结果表明，设置适量箍筋的空心墩在地震作用下具有良好的抗震性能。(d)当输入科比JMA记录时，桥墩在加载的早期阶段响应到极限状态。结果表明，正、负位移侧的恢复力是不同的。混合试验的恢复力与静载试验的恢复力不同。这表明荷载历史对钢筋混凝土结构的破坏过程有很大的影响，需要发展新的试验方法来评估地震荷载历史的影响。(e)钢筋混凝土空心墩的抗剪性能不容忽视。因此，仅考虑弯曲变形的分析方法对研究结构的性能具有局限性。因此，研究能考虑弯剪相互作用和循环荷载的分析方法具有重要意义。

In this research, the seismic performance of concrete piers with hollow sections were investigated. From this research, the following results are listed :(a) From the results of cyclic loading tests, it is found that the shear span ratio has a great influence on the failure pattern and deformation capacity. Therefore it is important to check the deformation performance of short piers of bridges across valley areas, since they usually consist of piers with different heights.(b) Under cyclic loading, it cannot be ignored a shear component of deformation of RC hollow piers.(c) From the results of hybrid earthquake loading tests, it was observed that the hysteretic response was stable and it can dissipate input energy by the hysteretic action. The RC hollow piers were found to have a good performance under earthquake motions if appropriate amount of hoops is arranged.(d) When inputting the Kobe JMA record, the pier responded up to the ultimate state in the early stages of loading. As the result, the restoring forces in the positive and negative displacement side were different. This restoring forces of hybrid experiment were different to that of static loading tests. This results suggest that the loading history has a great influence of the failure process of RC structures, and the new experimental method have to be developed to assess the effect of the loading history due to earthquakes.(e) The shear behavior of RC hollow piers is not neglected. Therefore the analysis which takes only account for the flexural deformation has the limitation for investigating the behavior. It is important to develop the analytical method which can take into account the interaction between flexure and shear, and the cyclic loading.