Seismic excitation of offshore wind turbines and transition piece response

Synopsis

Expansion of the offshore wind industry in seismically active areas has raised concerns regarding the structural integrity of offshore wind turbines under earthquake loading. This talk will report the recently published results of a 3D finite element study to investigate the behaviour of the structure, and in particular the transition piece, under seismic loads.

80% of currently installed offshore wind turbines are installed on monopile (MP) foundations, with a transition piece (TP) connecting the foundation to the superstructure. The most common type of MP-TP connection is a grouted connection, consisting of a cementitious ultra-high-strength grout cast between concentric steel tubes. More recently, design developments have allowed for the construction of the monopile and tower as a single piece (TP-less), with an associated predicted reduction in operational expenditure (OPEX) of 6-10%, and opportunity for significant life extension.

This talk will present a numerical study that assesses the seismic response of the transition piece and support structure of a representative 8MW turbine with both a grouted connection and TP-less design.

The talk will illustrate the potential gapping failure mode in the grouted connection under seismic excitation and assess cracking. The results will also illustrate the effect of the connection on the dynamic response of the structure and provide a comparison of the performance of a grouted connection with a TP-less design under seismic excitation.

Finally, the presentation will show the post-seismic monotonic response of both structures, including latent hub displacements, stiffness and strength.

About the Speakers

Dr Christelle Abadie  is an assistant professor in civil engineering at the University of Cambridge. She holds an Engineering degree from the French “Grandes Ecoles” ENSTA ParisTech, and a D.Phil from the University of Oxford. During her PhD, she studied the response of monopile foundations to long-term cyclic lateral loading (HARM model), and continued studying offshore wind monopiles through a PDRA at Oxford, working on the PISA2 project (Pile Soil Analysis). Her current research activities focus on geotechnics for sustainable infrastructure development in the context of climate change and include pile design under seismic loads for wind energy applications, onshore wind turbine foundation design and sensing of climate-change induced geo-hazards. Christelle is a fellow of Fitzwilliam College and works with a range of industry partners in order to ensure knowledge transfer from academia to practice

Chris Hamilton  is an engineer in the Specialist Structures and Mechanical group of Arup’s wider Technical Services portfolio in London. Chris holds an MEng from the University of Cambridge, where he specialised in Civil, Structural and Environmental Engineering, and conducted research with Dr. Abadie into the response of monopile-supported offshore wind turbines with grouted connections to seismic loads. Chris now works with a team of specialist engineers at Arup working in a variety of industries, but with particular focus on the design of offshore foundations for clients in East Asia. Chris has a specialism in nonlinear finite element analysis and integrated loads analysis of offshore wind turbine structures, and a strong interest in emerging technologies in the offshore wind industry

Further information

This event is organised by Offshore Engineering Society (OES). The event will be chaired by Phil Cooper (OES) . Attendance at this meeting is free for members and non-members alike. 

In person attendance

The event will held in-person at the Institution of Civil Engineers (see map below). Prior registration is not required. Seats are allocated on a first come, first served basis. We encourage everyone to attend in person if they can.

Online attendance

This event will be broadcast online. Please register for the event prior to joining. The registration process will provide you with the link you need to join the main event.

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