Cyclic lateral loading of monopiles for offshore wind turbines

This paper presents the results of implicit three dimensional soil-pore fluid finite element analyses investigating cyclic lateral loading on a 3.8mdiameter monopile in London Clay.The cyclic behaviour of the clay was simulated using the subloading tij constitutive model.Two-way and one-way cyclic lateral loads, representing offshore wind turbine production loading conditions, were applied to the monopile. Both cyclic loads were found to cause progressive accumulation of pile lateral displacement and rotation at mudline. However, the one-way load induced greater cumulative pile deformation in comparison to the two-way load.With each cycle, the rate of accumulation attenuated indicating an increase in the cyclic clay stiffness. A gradual increase in the pile shear force and bending moment, and low magnitude excess pore pressure build-up in the clay over each cycle, provided further verification of cyclic clay hardening