Seismic excitation of offshore wind turbines and transition piece response

Expansion of the offshore wind industry in seismically active areas has raised concerns regarding structural integrity turbines under earthquake loading. This paper details a 3D finite element study to investigate behaviour structure, and particular transition piece (TP), seismic loads. The work focuses on equivalent grouted connection TP-less designs, selected as promising design solutions for zones. numerical model is validated against medium-scale 4-point bending laboratory test, scaled up representative 8 MW turbine. results show that cracking grout occurs due excitation at top TP; location typically undamaged during monotonic can lead excessive settlement loss axial capacity caused by deterioration grout-steel bond water ingress. residual hub displacement after around 0.1 m. global response post-earthquake not significantly altered, with apparent stiffness ultimate strength maintained. An shown have 5% lower natural frequency than an design, suggesting reduced stiffness, damping absence grout. However, eliminates risk may therefore be safer option installed zones future.