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

本文对空心截面混凝土桥墩的抗震性能进行了研究。研究结果如下：(a)循环加载试验结果表明，剪跨比对破坏形态和变形能力有较大影响。因此，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十分重要。(b)循环荷载作用下，RC空心墩变形的剪切分量不可忽视。(c)混合地震荷载试验结果表明，结构的滞回响应是稳定的，滞回作用可以耗散输入能量。研究发现，在钢筋混凝土空心桥墩上适当布置箍圈，在地震作用下具有良好的抗震性能。(d)当输入神户JMA记录时，码头在加载初期响应到极限状态。因此，正位移侧和负位移侧的恢复力不同。混合加载试验的恢复力与静态加载试验的恢复力不同。结果表明，荷载历史对钢筋混凝土结构的破坏过程有很大的影响，必须发展新的试验方法来评估地震荷载历史的影响。(e)钢筋混凝土空心墩抗剪性能不容忽视。因此，仅考虑弯曲变形的分析对研究其性能有一定的局限性。发展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.