Numerical Analysis of Shear Keys for Offshore Wind Turbine Monopile Grouted Connection with Elastomeric Bearings

Abstract

Wind power is one of the best-known renewable energy sources, and it is mainly generated by wind turbines. With the recent development of large-scale offshore wind turbine technology and the improvements in capacity factor, the demand for offshore wind power is rapidly increasing for energy system applications worldwide. Such offshore wind turbine structures require structural capacity to withstand loads from offshore environments for a predetermined period of time. Generally, the load of the upper turbine system is transmitted through the grouted connection to the substructure. However, there are many cases of grout failure of the grouted connection between the tubular steels. This paper deals with the analysis of monopile grouted connections to which elastomeric bearings are applied. The grouted connection for the ultimate load of a 3.6 MW offshore wind turbine was analyzed using the three-dimensional finite element method. Furthermore, the changes in the contact pressure and shear stress were analyzed due to the installation of elastomeric bearings around the shear keys. As a result, when the elastomeric bearing was installed, the contact pressure for all grout contact areas increased about 2.5-fold. Specifically, the contact pressure with the shear key was 1.9-fold lower when natural rubber was used as the rubber plate material instead of chloroprene rubber. In addition, the maximum shear stress values of grout filler when installing the elastomeric bearings were 5.78 MPa for chloroprene rubber material and 4.90 MPa for natural rubber material, which were reduced by about 77–81% compared to the value of 25.95 MPa when only shear key was used.