A Macro-element Approach for Non-linear Response of Offshore Skirted Footings

Abstract

In recent times, shallow foundations have become more diverse, and now include concrete or steel bucket foundations used as anchors for floating platforms or as foundation for offshore wind turbines. They are always subjected to significant cyclic lateral loads due to wind and wave action. A work-hardening plasticity model for the moment and horizontal force resultants associated with the displacements of the offshore suction caissons is herein developed. In addition, in order to better understand the performance of offshore bucket foundations under cyclic lateral loads series of cyclic lateral load tests were carried out on small scale models in a special rig developed for the cyclic tests at Aalborg University. The influence of cyclic lateral loads on the bucket lateral secant stiffness is investigated and a function is utilized to investigate it due to permanent displacements. The bucket stiffness increased with number of cycles irrespective of the load characteristics which contradicts the traditional solutions to tackle this complex situation.