Wind turbine performance under multi-hazard loads: Wave, wind, and earthquake effects on liquefiable soil

• Evaluating the influences of several key factors on the seismic response of offshore wind turbines in the liquefiable soil using 3D parallel finite element analysis. • Consideration of monopile-soil interaction through a multiple yield surface plasticity model for soil, implemented in OpenSees. • Application of the Pierson-Moskowitz spectrum and diffraction theory for the calculation of random wave forces. • Investigation of the combined effects of earthquake, wind, and wave loads on the amplification of OWT responses. • A moderate to strong earthquake can cause liquefaction of saturated sand, leading to significant OWT responses even with weak wave/wind loads. This research studied the seismic performances of offshore wind turbines (OWT) on monopiles in liquefiable soil under separated and combined loads of waves, winds, and earthquakes following the simultaneous occurrence of these natural phenomena in maritime regions. TCL programming language was used to create several 3D parametric models, which were then analyzed using OpenSees software. The focus was on the influences of the induction factor, wind speed, wave height, prominent wave period, frequency contents, and simultaneous loads on the resulting system response. The results show that the OWT responses increase with wind velocity, and wave height. In addition, a moderate to strong earthquake has the potential to induce liquefaction in saturated medium sand layers. This phenomenon can lead to a more substantial response in the OWT, even in the presence of minimal wave or wind loads. In most cases, the combination of earthquake, wind, and wave amplified the OWT responses, so it is necessary to consider the combined load influences in the analysis and design.