Reliability Analysis of Monopile for Offshore Wind Foundation Using the Response Surface Method

Abstract

One of popular offshore wind turbine foundations, monopile has been largely used because of their cheapness and constructability. Monopile is subjected by large cyclic lateral loadings such as wind, wave and current. P-y curve method which represents a relationship between lateral pile displacement and passive soil resistance along the leading face of the pile is known as a highly reasonable method to analyses lateral behaviors of pile. Performing reliability analysis of a monopile foundation using nonlinear p-y curves is difficult because the limit state functions (LSF) of pile head deformation and rotation angle of pile are in implicit forms. To solve such problem with implicit LSF, a response surface method (RSM) could be used. Basic concept of RSM is to approximate the limit state boundary using an explicit function of the random variables. In case of using RSM, reliability analysis could be very simple, but the accuracy of analysis due to approximation depends much on the linearity of the LSF and on the distance of the axial points in the failure space. This paper investigates the best combinations of the RSM techniques with a reliability analysis of monopile for an offshore wind foundation. represents a relationship between lateral pile displacement and passive soil resistance along the leading face of the pile is known as a highly reasonable method to analyses lateral behaviors of pile. Performing reliability analysis of a monopile foundation using nonlinear p-y curves is difficult because the limit state functions (LSF) of pile head deformation and rotation angle of pile are in implicit forms. To solve such problem with implicit LSF, a response surface method (RSM) could be used. Basic concept of RSM is to approximate the limit state boundary using an explicit function of the random variables. In case of using RSM, reliability analysis could be very simple, but the accuracy of analysis due to approximation depends much on the linearity of the LSF and on the distance of the axial points in the failure space. This paper investigates the best combinations of the RSM techniques with a reliability analysis of monopile for an offshore wind foundation.