Seismic response of hybrid pile-bucket foundation supported offshore wind turbines located in liquefiable soils

Abstract

An increasing number of offshore wind turbines (OWTs) are constructed globally because of their capability of producing clean and green energy. Many of these structures located have already been or will continue to be constructed in the earthquake-prone areas with the possibility of soil liquefaction. The hybrid pile-bucket foundation consists of a traditional monopile and a wide-shallow bucket and is an innovative foundation when used to support OWTs. The dynamic behavior of the hybrid pile-bucket foundation supporting the OWTs in liquefiable soils under earthquake loads is investigated in the present study. In order to further explore the superiority of the hybrid foundation, two three-dimensional (3D) numerical models of a 5-MW offshore wind turbine supported by monopile and pile-bucket foundation in the liquefiable soils are established respectively based on the open-source software platform OpenSees. The liquefiable soils are discretized by brick u-p elements and its constitutive behavior is modelled using PDMY02 material model in OpenSees. The seismic responses of the OWTs under two ground motion records with different peak accelerations and frequency components are investigated in this study. The results indicate that the hybrid pile-bucket foundation can significantly decrease the seismic responses of the OWTs and increase the liquefaction resistance of the surrounding seabed, compared with monopile foundation.