Seismic Evaluations of Pile Foundations with Three Different Methods Based on Three-Dimensional Elasto-Plastic Finite Element Analysis

Abstract

In this paper, three methods for seismic evaluation, namely, a separated method using a dynamic analysis on a simplified sway-rocking model (S-R model), a responding displacement method, and a dynamic analysis on a full system, are investigated by conducting a series of static and dynamic three-dimensional elasto-plastic finite element analyses. At first, the validity of a newly developed finite element analytical code DGPILE-3D, which is used throughout this paper, is checked through a dynamic model test on a pile foundation. Then, an elevated railway bridge with a pile foundation is investigated with the separated method and the responding displacement analysis, which are often used in seismic design, and a three-dimensional elasto-plastic dynamic analysis on a full system. Two types of ground are considered in order to understand the influence of the soil on the mechanical behaviors of upper structures and pile foundations. From these analyses, it is possible to understand the difference of the mechanical behaviors of pile foundation predicted by different methods. Based on the results obtained in this paper, fundamental knowledge needed for developing an applicable and easily conducted seismic design method with three-dimensional finite element analysis, is achieved.