ABSTRACT
Understanding of dynamic response of offshore wind turbine is important to evade structural hazards by dynamic loadings such as resonance vibration and earthquake. Although dynamic characteristics of the offshore wind turbine are affected by soil stiffness and foundation type, there have been only a few experimental studies on this subject to supplement and calibrate the analytical studies considering soil-foundation-structure interaction (SFSI). Geotechnical centrifuge experiment can provide reliable experiment result as it can reproduce field stress condition of the soil with a scaled model test. The goal of this research is to evaluate the natural frequency and seismic behaviour of the offshore wind turbine for monopile, monopod, and tripod foundation considering SFSI by geotechnical centrifuge test. Natural frequency was evaluated in fixed-based scaled model test and SFSI geotechnical centrifuge test to evaluate the period lengthening due to SFSI. Results showed that if the same amount of material was invested, Tripod foundation showed most stiff behaviour. Also, monopile and monopod test results were compared with existing analytical evaluation method. Results showed less than 6% difference in period lengthening ratio (PLR). Seismic behavior was evaluated by applying series of seismic loadings and measuring the structural acceleration, permanent rotational displacement. The result showed that difference in seismic behaviour by foundation types should be considered.
