Experimental and numerical study on dynamic response of offshore wind turbine subjected to earthquake loads

In order to investigate the response of offshore wind turbines (OWTs) under earthquake, shaking table test is conducted using a 6.45 MW OWT as prototype. The effective length of the embedded steel pile is determined using the equivalent embedment method, and a scale model with a similarity constant of 1:15 is designed. The dynamic characteristics of the scale model are evaluated through position-shift and white noise. Three earthquakes with different spectrum characteristics are utilized as inputs, and subsequently, an analysis is performed to assess the earthquake response of the OWT. The results demonstrate that the dynamic characteristics between the scale model and the prototype model meet the similarity constants. Due to the eccentric mass, torsional vibrations are induced when subjected to bidirectional excitation, resulting in the occurrence of 'beat vibration' phenomenon. The acceleration is significantly influenced by the excitation spectrum, with the maximum occurring at either the top or 2/3 height, and Darfield with wide spectrum result in a more pronounced stimulation. The displacements are all observed at the pinnacle of the tower. The Imperial and Kocaeli, characterized by shorter duration and higher energy concentration, elicit more pronounced displacement. Stress concentration occurs at the lower 1/3 due to sudden stiffness change.