Effect of uncertainty on the seismic behaviour of fixed pile-founded offshore platforms

Abstract

ABSTRACT Fixed pile-founded offshore platforms require careful consideration during their analysis, design, and assessment because uncertainty in design variables can decrease the reliability of the structures. The present study investigated the sensitivity of seismic engineering demand parameters to stochastic and epistemic modelling variables for a fixed pile-founded jacket platform. Tornado diagram analysis and the first-order second-moment techniques were employed to examine the effects of 11 variables on engineering demand parameters under real earthquake loads and the importance of each variable was determined. As the nonlinear response of the pile foundation is a crucial source of nonlinearity in offshore platform response, a robust model considering soil–pile–structure–fluid interaction was employed. This study varied from previous research as it employed a three-dimensional model, fluid environment modelling, and earthquake actions in perpendicular directions. These differences resulted in more realistic approximations of the seismic behaviour of the platforms. It was found that the effects of different variables, especially water depth, should be considered in order to produce better performance evaluations of a structure for a more efficient and cost-effective design.