Pile foundation in soft ground usually will be subjected to a lateral cyclic loading during an earthquake. In a major earthquake, it is reasonable to think that the mechanical behavior of a pile foundation and the surrounding ground is nonlinear. In recent years, the limit state design method became predominant in the design of foundations of toll bridges and other structures. The investigation on the mechanical behavior of pile foundations subjected to lateral cyclic loadings up to an ultimate state, therefore, is very important to provide evidences for the designing method. In this paper, a real scale field test of a 9-pile foundation, with a pile diameter of 1.2 m, subjected to cyclic lateral loading up to an ultimate state, is simulated using a 3- dimensional elasto-plastic finite element analysis (DGPILE-3D). The nonlinear behavior of RC pile is simulated with an axial-force dependent hysteretic model proposed in this paper. Meanwhile, the soil of the ground is simulated with Drucker-Prager model. The purpose of the paper is to provide an applicable numerical way of evaluating the mechanical behavior of a pile foundation subjected to cyclic lateral loading up to an ultimate state.
In seismic evaluation of pile foundations, it is necessary to clarify the mechanical behaviors of both pile and ground subjected to cyclic lateral loading at ultimate state. Many researches have been done on this subject experimentally and analytically. Brown et al. (1987) conducted a test on a large-scale pile group subjected to cyclic lateral loading. Kimura et al. (1991) developed a 3-dimensional static finite-element-analysis program (GPILE-3D) in which the stress-strain relation of the ground was simulated with Drucker-Prager model in monotonic loading condition. Later, various improvements were added to the program (Adachi et al., 1994), (Kimura and Zhang, 1997), (Kimura and Zhang, 1999).
