Grouted connections on offshore wind turbines: a review

Grouted connections (GCs) have been extensively used in offshore applications over the last decades and are widely used today in offshore monopile wind turbines. The effectiveness of the connections on monopiles was questioned recently after several substructures were reported to have insufficient performance in wind farms over Europe. This paper brings together the current practice in terms of engineering methods used for the determination of loads acting on the structure and the numerical methods used for the investigation of the structural behaviour of the GC. With respect to hydrodynamic loads on monopile wind turbines, the popular linear wave theory along with the Morison equation can be used to model normal sea states, whereas higher-order wave models are necessary to investigate severe events such as wave breaking. In terms of wind loads, blade element momentum proves to be advantageous with respect to computational cost and ease of implementation in simulation tools. Finally, finite-element modelling of GCs is introduced and close attention is given to the non-linearity of the grout material and the interface contact which are considered to be decisive aspects for the structural analysis.