A Three Dimensional Comparative Study of Seismic Behaviour of Vertical and Batter Pile Groups

To a practicing foundation engineer, the performance of batter pile under seismic conditions still remains a questionable prospect. The contradictory findings reported by various investigators with regard to the performance of batter piles add to this dilemma. This calls for a rigorous three-dimensional investigation to evaluate seismic behavior of batter pile groups. In this study, a comparative assessment of three-dimensional seismic behavior of a 2 × 2 vertical and batter pile groups having batter angle of 15° was carried out using a full three-dimensional finite element code developed in MATLAB (Sarkar 2009). The effects of centre to centre spacing of piles and soil modulus values were investigated. Idealized soil profiles having constant and triangular variation of soil modulus were adopted for the study. Results of analyses for both the vertical and batter pile groups are presented in terms of dynamic stiffness and kinematic interaction factors. Results indicate better seismic performance of batter pile groups in comparison to that of vertical pile groups. To demonstrate the importance of the findings, a five-storied portal frame structure supported separately on vertical and batter pile groups were considered and analyzed for El-Centro Earthquake (1940) time history. The difference in structural response considering vertical and batter pile groups is highlighted.