In this dissertation, structural wind turbine blade layouts are presented that are suitable for 10MW and 20MW wind turbine blades. This has been accomplished by using a medium fidelity static aeroelastic model embedded in an optimisation framework. The structural solutions are the result of a stiffness optimisation where the blade mass is minimised. To accomplish the structurally optimised blade, an aeroelastic analysis model is set up. This model consists of a nonlinear structural analysis module and an aerodynamic module. Both models are comparable in terms of the level of physical modelling and as such, it can be said that both models are of equal fidelity. This equal fidelity is favourable for the aeroelastic coupling between both models, which generates an aeroelastic solution that is accurate up to the level of physics present in the aerodynamic and the structural models...@en