Ultimate strength characteristics of cylindrical shell in combined compression and bending moment

Many countries have set out their commitments for net-zero emission in order to address the increasingly detrimental impact caused by greenhouse gas and the consequent climate change. To accelerate the ambitious net-zero target while ensuring a sufficient energy supply, the exploitation of wind energy is one of the sustainable and clean solutions. Thus, it is foreseen that the investment in the offshore wind will continue worldwide in the coming years. For a successful deployment of offshore wind turbines, an adequate safety margin of their foundation supporting structures is of paramount importance. Prevailing design codes require a rigorous assessment against the ultimate limit state for the foundation supporting structures of offshore wind turbines. These structures are typically in the form of cylindrical shells, which are subjected to a combination of axial compression and overturning bending moment. In this paper, a numerical study is presented in the light of gaining better insights into the catastrophic collapse behaviour of cylindrical shells under combined loads. Nonlinear finite element analyses considering geometric and material nonlinearities are completed on a parametric range of structural models with different length-to-radius and radius-to-thickness ratios. A matrix of axial compression and bending moment combinations are analysed. The numerical results are compared with prediction by prevailing code formulae.