Performance-Based Design for Earthquake-Induced Liquefaction: Application to Offshore Energy Structures

Liquefaction has been a major challenge to design of structures founded on loose silt and sand in moderate and specially highly seismic regions. While assessment of liquefaction susceptibility and potential have been largely based on empirical methods, the design of structures on liquefiable soil requires reliable numerical tools and clear performance criteria. In this paper, solutions are provided based on the well-established SANISAND model and its more recent extension, SANISAND-MSu, implemented in the open-source finite element platform OpenSEEs. Applications are presented for structures commonly encountered in offshore energy sector such as conventional subsea facilities on mudmats and offshore wind turbines founded on large-diameter monopiles. The impact of pore-water pressure, and ultimately liquefaction, on the offshore structures is assessed by performing both quasi-static cyclic loading and earthquake shaking. The general behavior of these offshore structures during liquefaction are presented from a numerical modelling perspective. The simulation results indicate that the response of these structures is considerably affected by structural features and environmental loading conditions. The results presented in this work motivates the use of SANISAND-MSu model in enhanced 3D finite element modelling in offshore structural dynamic analyses.