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.
Highlights
Offshore wind is a renewable energy technology with an important role in current and future energy systems [1,2,3]
The offshore wind monopile substructure consists of a monopile (MP) and transition piece (TP), and the turbine system refers to the blade, nacelle, hub, and tower
Monopile grouting is a method wherein an MP is inserted into the seabed, the TP is mounted on the outside of the MP, and the two tubular steel members are integrated [6]
Summary
Offshore wind is a renewable energy technology with an important role in current and future energy systems [1,2,3]. Elastomeric bearings are laminated rubber bearings widely used to reduce the response of structures due to their excellent deformability, stable mechanical properties, and low manufacturing cost [11] If such an elastomeric bearing is installed around the shear keys of the GC, it is expected that the repeated or extreme shear force concentrated on the shear key will be dispersed, preventing the failure of the grout material or contact. Uncertainties of several parameters exist in the capacity evaluation of GCs. Uncertainties relate to the element type, element quality in the stress concentration region, coefficient of friction, grout material properties, material modeling, and contact formulas.
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