Centrifuge modeling to evaluate natural frequency and seismic behavior of offshore wind turbine considering SFSI

Understanding of dynamic response of offshore wind turbine is important to reduce vibration of offshore wind turbine induced by structural and environmental loadings. Although dynamic characteristics of the offshore wind turbine such as natural frequency and seismic behavior are affected by foundation and soil conditions, there are little experimental studies about the dynamic behavior of offshore wind turbine with consideration of proper soil-foundation-structure interaction (SFSI). The goal of this research is to evaluate the natural frequency and seismic behavior of offshore wind turbine with a monopod foundation considering SFSI. Scaled model of offshore wind turbine and monopod foundation is produced for this research. Geotechnical centrifuge tests in fixed-based and SFSI condition were performed to measure natural frequency in each case. Also, a series of seismic loadings with different intensities are applied to observe seismic behaviors of the offshore wind turbine during the earthquake and permanent changes after the earthquake. Experimental results show apparent natural frequency reduction in SFSI condition compared with the fixed-based condition, non-linear changes in dynamic response during a series of earthquakes and permanent changes occurred in natural frequency and rotational displacement after earthquakes. Copyright (c) 2017 John Wiley & Sons, Ltd.