Effects of constitutive soil models on the seismic response of an offshore jacket platform in clay by considering pile-soil-structure interaction

Offshore jacket platforms are widely used for wind energy generation and gas and oil field development. The South Pars gas field, located in the Persian Gulf, stands as one of the largest gas fields in the world. This gas field is situated in a seismically active region predominantly characterized by clay soil. Considering the significant impact of clay soil on the seismic response of offshore structures and their vulnerability to damage, it is essential to conduct comprehensive studies on the seismic behavior of offshore structures in this particular area while considering the nonlinear behavior of soil and pile-soil-structure interaction (PSSI). However, due to the laboratory limitations, it is difficult to experimentally investigate the seismic behavior of these structures on a real scale by considering the actual soil environment. This paper aims to adopt a nonlinear kinematic hardening model for clay in Abaqus software and calibrate this model parameters for the South Pars gas field region to carefully investigate the effects of nonlinear behavior of soil and PSSI on the seismic response of an offshore jacket platform. In addition, the perfectly elasto-plastic Mohr-Coulomb model is employed as a simple and common constitutive soil model to compare the results. To achieve the study goals, firstly, the numerical modeling techniques are validated. Subsequently, the main parameters of the nonlinear kinematic hardening model are calibrated for the South Pars gas field region, which has not been done for this region in previous works. Detailed numerical models, including the fixed-base model and the pile-soil-structure (PSS) model, are then developed and analyzed using different selected ground motion records. The results indicate that considering the effect of PSSI has a significant effect on the seismic responses of the structure. Moreover, PSSI effect has a great dependence on the constitutive soil model. The results of this study are expected to provide useful insights into the seismic design of offshore structures in similar geological conditions.