Calculation of monopile foundation in sand to long-term lateral cyclic load

Monopiles are widely used to support the upper structures of wind turbines in offshore engineering. Due to harsh environmental conditions, they are subjected to long-term lateral cyclic loading from waves and winds during the design life. A robust beam on the Winkler foundation model is presented to analyze the responses of monopile foundation under long-term lateral cyclic load, incorporating cyclic stiffness evolution of sand based on the results of drained cyclic triaxial tests. The reasonability of the model is proved by comparison with a published centrifuge model test. Furthermore, a parametric analysis is performed to study the effects of pile diameter, pile eccentricity, embedment depth and cyclic load amplitude to the accumulation of deformation at the pile head during the long-term lateral cyclic load, based on which an empirical expression for estimating the accumulated displacements of a long-term lateral loaded monopile under cyclic loads is given.