Seismic analysis of a monopile-supported offshore wind turbine considering the effect of scour-hole dimensions: Insights from centrifuge testing and numerical modelling

Abstract

Monopile-supported offshore wind turbines (OWTs) deployed in seismic-active regions are inevitably threatened by the combined effect of earthquake and scour. However, current codes and research fail to adequately address the seismic response of OWTs under different scour conditions. In this study, a series of centrifuge shaking table tests were conducted on a monopile-supported OWT model subjected to both local scour and general scour. The test results show that the amplification effect of general scour site is more pronounced than that of local scour site. Moreover, the maximum bending moment from the general scour cases are mostly larger than those from the local scour cases under relatively large scour depth. This indicates the possibility of an over-conservative design when simply reducing the local scour condition to general scour condition. Then, based on the centrifuge tests, a practical 2D finite element model is proposed, in which not only the inertial and kinematic effects but also the effect of scour-hole dimensions on the ground motion input pattern and the vertical effective stress along the pile are incorporated. Further parametric study shows that the kinematic effect plays a significant role in the pile response and cannot be simply neglected even under scoured conditions.