Ultimate strength assessment of jacket offshore wind turbine support structures subjected to progressive bending loading

The present study aims to assess the ultimate strength of a jacket offshore wind turbine support structures at different water depths. The progressive collapse analysis is carried out based on the finite element method accounting for the nonlinearities regarding material and geometry. A two-step analysis is carried out, in which at first, the axial dead loads are applied in a linear quasi-static analysis and then the resulting pre-stressed jacket support structure is analysed by a nonlinear finite element analysis in order to identify the ultimate strength. The present study employs a global strength approach so as to assess the ultimate strength of the jacket support structures consisting of several supporting modules with different stiffness. The moment-curvature relationships are presented for the jacket support structures at water depths of 40, 60 and 80 m. The effects of the thickness and leg inclination on the ultimate strength are investigated.