Seismic Performance of Multimegawatt Offshore Wind Turbines in Liquefiable Soil under Horizontal and Vertical Motions

Abstract

Various multimegawatt capacity offshore wind turbines (OWTs) are constructed globally to fulfill increasing energy demand. Many of these structures have already been and will continue to be constructed in seismically active areas. Hence, these structures are at probable risk of an earthquake. The dynamic behavior of monopile-supported various multimegawatt OWTs in liquefiable sand deposit under combined action of operational and seismic loads are investigated in this study. A three-dimensional beam on a nonlinear Winkler foundation model is developed in OpenSees. The monopile and the tower are modeled as a linear Euler–Bernoulli beam. The lateral and vertical pile–soil interfacing behavior is modeled by using p-y, t-z, and q-z spring elements. The strong ground motion is utilized as free-field displacement at spring supports. The effect of the vertical component of seismic motion on the performance of the OWT structure in liquefied soil is examined.