ABSTRACT

The seismic behavior of a structure is affected by many factors, which include oscillation properties of the structure, seismic properties of the ground surrounding the structure and so on. If the structure is supported by piles, the interactions among the structure, the pile foundation and the ground may be an important factor to be added. In this system, the pile foundation assumes a key role as a transmitter of seismic energy from ground motion to the structure or a pathway sending vibration energy of the structure to the ground. The purpose of this study is to evaluate comprehensively the influences of various factors like ground properties, types of structures and piles on the behaviors of structures during earthquakes. A series of vibration analysis for a system of structure-pile foundation-ground using a spring mass model was carried out. In the analysis, four kinds of simplified ground profiles, two types of seismic motions, five types of building heights and five types of pile lengths were used, respectively. The results of the analysis were evaluated through the principal component analysis and classified into four groups using two principal components obtained in the analysis. The influences of various factors on seismic response characteristics of the buildings were discussed with the results of the principal component analysis. From the results, the ratio of pile length to building height was an important factor for the responses of buildings. It was also found that the effects of radiation damping increased as the ratio was increased.

INTRODUCTION

The seismic behavior of a structure is affected by many factors, including oscillation properties of the structure and seismic properties of the ground surrounding the structure. Especially, a seismic affinity between types of structure and ground is so important that it can dominate damage level of the structure.

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