MECHANICAL BEHAVIOR OF PILE FOUNDATIONS SUBJECTED TO CYCLIC LATERAL LOADING UP TO THE ULTIMATE STATE

FENG ZHANG, MAKOTO KIMURA, TERUO NAKAI and TAKUYA HOSHIKAWA

ABSTRACT Pile foundations in a soft ground will usually be subjected to lateral cyclic loading during earthquakes. In a major earthquake, it is reasonable to think that the mechanical behavior of the pile foundation and the surrounding ground is nonlinear. In recent years, the limit state design method has become predominant in the design of foundations for railway bridges and other structures. Investigations of the mechanical behavior of pile foundations subjected to lateral cyclic loading up to the ultimate state, therefore, are very important in providing evidence for the design method. In this paper, field tests on a pile foundation, composed of cast-in-place reinforced concrete piles and subjected to one-side cyclic lateral loading up to the ultimate state, are simulated with the three-dimensional elasto-plastic finite element analysis (DGPILE-3D). In the numerical analysis, particular attention is paid to the stress-strain relation of the soil which, to the author's point of view, plays a dominant role in the mechanical behavior of the pile foundation. Such constitutive models as the Drucker-Prager model, Cam-clay model, and t_ij model are adopted for the analysis in order to find the differences in the results due to the application of different constitutive models. Based on the analysis, the authors try to provide an applicable numerical way of evaluating the mechanical behavior of a pile foundation subjected to cyclic lateral loading at the ultimate state.

Key words: elasto-plasticity, finite element method, foundation, lateral loading, pile (IGC: E4)