近场地震下考虑桩-土-框架结构相互作用的拟动力试验

Pseudo dynamic experimental analysis of pile-soil-frame interaction in near-fault earthquakes

考虑桩-土-结构相互作用,建立整个结构体系模型,在土槽实验室模拟框架结构在近场地震作用下的反应。由于下部结构的不可控性和土体的不确定性,提出采用反演分析识别下部结构的动力反应。试验中通过传感器有效的获取下部结构状态信息,确定桩-土工作状态,运用子结构的概念完成整个结构体系的拟动力试验。利用实验室大型土槽,设计一个以钢管桩为基础的8层框架结构,探讨脉冲型地震和常规地震下作用下钢筋混凝土框架结构的反应。通过对比结构的破坏形态、底层的位移时程曲线和滞回曲线得到:脉冲型地震作用下,结构的反应远远大于常规地震下的反应;高强度的速度脉冲将引起结构产生更大的残余变形,同时结构有更高的位移需求。分离出基础引起的结构变形,基础的转角将大大增加结构的顶点位移,并且近场地震放大作用更加明显。

A test system with pile-soil interaction was built based on the concept of the substructure for the assessment of frame structure under near-fauh earthquakes. An inverse model was proposed to identify the dynamic response from the substructure. The model, which relates sensor＇ s data to the working state of soil and piles in a test system, was used to reduce the errors caused by uncontrollability of substructure and uncertainty of soil. An eight-story frame structure with steel pipe piles was designed in the large-size soil tank, and the structure response under normal earthquakes and near- fault earthquakes were compared in two test substructures. The tests show that due to the high-intensity velocity pulse in near-fault earthquakes, the bottom-level displacement history and force-displacement curves were much larger, and more residual deformation and displacement demand were found. Based on the test data, the separated base-rotation-induced top displacement of the upper structure took a large proportion of the total displacement, especially for the near-fauh earthquakes.