Seismic response and liquefaction characteristics of wide and shallow multi-bucket jacket foundation under scour conditions

Abstract

Scour has a significant effect on the seismic response of offshore structures. Compared to monopiles, MBJFs are shallow foundations and scouring has a more detrimental effect on their earthquake performance. However, the combined impacts of scour and earthquake on the structural response and liquefaction characteristics of the MBJFs have not been completely investigated. Based on the secondary development of the ABAQUS program, this paper proposes a method for calculating the seismic response and liquefaction of MBJF under local scour conditions. The seismic response and liquefaction characteristics of MBJF-supported OWTs in silty soil are evaluated under different scour depths, scour ranges, earthquake motions, soil conditions, and structural damping. In comparison to the unscoured condition, the results show that the maximum horizontal displacement, lateral acceleration, and bending moment of MBJF-supported OWTs increase by 30%, 97%, and 58%, respectively. Liquefaction is generated mostly in the soil outside the bucket rather than inside. An increase in soil density can improve the lateral acceleration of the structure and reduce the proportion of liquefaction in the soil. The maximum reduction in liquefaction can be 70.2% for an increase of 23% in soil densities. Disregarding structural damping will overestimate the structural response and the proportion of soil liquefaction. The findings may shed light on the seismic response and liquefaction characteristics of MBJF-supported OWTs located in complex offshore scour environments.