Earthquake Response Analysis of Whole Structural System for Reinforced Concrete Structures

最近的地震强调了对包括结构、基础和地基在内的整个结构体系进行响应分析的重要性，以进行基于性能的结构设计。然而，为了开发一种现实的分析方法，首先必须弄清楚桩和土在地震期间的行为。本研究的主要目的是通过足尺水平荷载试验研究混凝土桩和土的抗震性能，并建立基于试验的分析程序。对埋入粘性土中的混凝土桩进行了足尺水平荷载试验。其中两根桩采用内钻孔技术埋入地面，另外两根桩采用外钻孔技术，在桩和土周围使用膨润土-水泥浆。试验结果表明，与单调荷载相比，在循环荷载作用下，桩的水平承载能力显著降低。然后进行了三维非线性有限元分析，对试验试件的性能进行了解析研究。分析表明，桩与土面之间应采用界面单元来模拟土与桩之间的缝隙形成。此外，分析还表明，如果忽略循环荷载引起的土体刚度退化，则分析高度高估了桩的水平承载能力。研究还发现，对于钻孔灌注桩，在分析中必须考虑膨润土-水泥层，才能得到桩的实际水平性状。

Recent earthquakes have stressed the importance of conducting response analysis of a whole structural system including structure, foundation and ground for the performance based design of a structure. For the development of a realistic analytical method, however, it is first imperative to clarify the behavior of pile and soil during earthquakes. The main objectives of this research are to study the seismic behavior of concrete pile and soil using full-scaled lateral loading test and to establish an analysis procedure based on the experiment. Full-scale lateral loading tests were carried out on concrete piles embedded into cohesive soil. Two of the piles were embedded into the ground using inside drilling technique, whereas other two piles were embedded using outside drilling technique with bentonite-cement paste around the pile and soil. The results of the experiments revealed that the lateral load carrying capacity of piles significantly degrades when subjected to cyclic loading compared to the monotonic loading. Three-dimensional non-linear finite element analysis was then carried out to study the behavior of experimental specimens analytically. The analysis implied that interface element should be used between pile and soil surface to simulate the gap formation between the soil and pile. Moreover, the analysis also showed that if the degradation in soil stiffness due to cyclic loading is ignored, the analysis highly overestimates the lateral loading capacity of the pile. It was also found that for the outside-boring pile, bentonite-cement layer has to be considered in the analysis to obtain the actual lateral behavior of pile.