Accelerated analysis on cyclic response of large-diameter monopiles offshore wind turbines in soft clay

Large-diameter monopiles serve as a widely adopted foundation form for offshore wind turbines. Throughout their service life, offshore wind turbines are subjected to millions of cycles of wind and wave cyclic loads, which induces long-term accumulated deformation of the monopile foundation and restricting the normal operation of the superstructure. To improve computational efficiency under multiple cyclic loading conditions, this paper conducts an accelerated finite element analysis of the long-term cyclic response of large-diameter monopiles in soft clay. The approach is based on an undrained cyclic bounding surface model for soft clay and employs extrapolation of the cumulative plastic strain rate in the soil around the pile. The reliability of the accelerated computation method is verified through comparison with cyclic triaxial tests. Subsequent accelerated finite element analyses of the cyclic loading response of large-diameter monopiles show that this method can effectively predict the accumulated deformation at the pile head and the development of soil plastic zones, with results consistent with centrifuge model tests and empirical formulas. Computational efficiency is improved by more than tenfold. This study provides an efficient and reliable numerical simulation approach for analyzing the long-term cyclic response of pile foundations.