Seismic Modelling of Monopiles under Wave Load in the Sandy Soil

Human growing demand for energy and in recent decades for clean and renewable energy, leading to the development of wind farms inshore areas and have moved to offshore areas to achieve more production. Noticed that wind farms are a series of large, expensive and same structures, their foundations are important and it’s necessary to minimize the probability of failure all of them. Many wind turbines are founded on large piles called monopiles. In European countries particularly in offshore areas, dominant environmental loading on monopiles is the wave. But some of the pioneer countries in wind energy development, such as China, India and the United States are highly seismic areas. Following the occurrence of natural events of wave and earthquake in the sea at the same time, considering the behavior of monopiles under their combined effects are required. In this study, three-dimensional modeling of the soil-monopile system using Open Sees software by finite element analysis was carried out and the effect of wave load on seismic responses of monopile and its surrounding soil was investigated. The wave and earthquake loads applied simultaneously on the soil-monopile system. In the nonlinear behavior modeling for sandy soils, effects of the stiffness, permeability, dilation, and potential of soil compaction on system responses are included. Studies have shown that wave can be affected on the seismic responses of monopile significantly, in addition to amplification of monopile, rotation, shear force and bending moment, can change the location of maximum moment and shear in monopile.