Non Linear Seismic Pile Soil Structure Interaction Analysis of Piles in Offshore Platforms

Abstract

Pile supported offshore platforms in seismically active areas should be designed to survive severe earthquake excitations with no global structural failure. It is often required to perform nonlinear seismic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural nonlinear behaviours of the piles. In this study a BNWF (Beam on Nonlinear Winkler Foundation) model is incorporated into a finite element program (ANSYS) and it is used to compute the lateral response of piles subjected to seismic loading. The soil stiffness is established using the P-Y curve. The results of equivalent linear earthquake free field ground motion analyses are used as the input excitations at support nodes of the model. The components and advantages of this practical ANSYS model in seismic pile soil structure interaction analyses are discussed and addressed in detail. Computed responses compared well with the experimental test results. Sensitivity of the results to model parameters and site response calculations are evaluated.