Earthquake Response Analysis of Whole Structural System for Reinforced Concrete Structures

近年来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反应分析对于结构性能设计的重要性。然而，为了发展一种现实的分析方法，首先必须澄清地震过程中桩土的行为。本研究的主要目的是利用足尺横向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方法。对混凝土桩嵌入粘性土中进行了全尺寸横向荷载试验。其中2根桩采用内钻法嵌入地基，另外2根桩采用外钻法嵌入地基，桩周围采用膨润土水泥浆。试验结果表明，与单调荷载相比，循环荷载作用下桩基的横向承载能力明显下降。然后进行三维非线性有限元分析，对试验试件的行为进行解析研究。分析表明，应采用桩与土表面之间的界面单元来模拟桩土间隙的形成。此外，分析还表明，如果忽略循环荷载引起的土体刚度退化，则分析严重高估了桩的侧向承载能力。对于外钻孔桩，在分析时必须考虑膨润土-水泥层，才能得到桩的实际侧移特性。

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.