Wind energy is currently a crucial player in the global transition toward sustainable and renewable energy sources. With the new geopolitical strategies, the focus on renewable energy intensifies, bringing out the role of wind energy and the investment in offshore wind turbine energy sector in order to secure a diversified and sustainable energy future. This thesis presents a structural optimisation of a semi-submersible floating platform for offshore wind turbines following the novel methodology introduced in the study "Definition of a reference model for structural finite element analysis of an offshore wind turbine floating foundation". Firstly, an overview of wind energy is presented, with a special focus on the evolution of offshore wind energy and the new trends due to the latest plans and agreements.