Enhanced multi-springs model for estimating suction caisson responses under cyclic lateral loading

Abstract

Offshore wind turbines (OWTs) are situated in intricate marine environments and consistently subjected to cyclic loadings, leading to an accumulation of foundation displacement along with stiffness variation. Employing the multi-spring system, improvements are made to the p-y and t-z model of multi-springs, according to the bounding surface plasticity-based theory, supporting the ongoing loading and unloading behaviors at the caisson-soil interface, which is also verified by the monopod caisson's tests under both uni-directional and multi-directional cyclic lateral loadings. The comparative analysis further indicates that ignoring the combined effect of p-y and t-z springs may result in overstating the deformation of the caisson. Then, incorporating the enhanced multi-spring model into the soil-structure module, allows for the implementation of the dynamic analysis procedure designed for caisson-based OWTs under multi-directional cyclic lateral loading. An increase in the cycle count leads to a larger load deflection angle for the case studied, initiating a continuous accumulation of plastic displacement and the disturbance at caisson-soil interface. This process gives rise to a certain degree of shrinkage within the soil stress boundary, ultimately affecting the overall stability of the structure.