Abstract
In the previous chapters, the loads and load cases important for offshore energy structures are discussed. To assess the functionality and structural integrity of a design, it is needed to predict the motion and structural responses. A reliable and robust design should be based on accurate calculation of loads and responses. Offshore energy structures are complicated, respect to the dependency of loads and load-effects. In these cases, the response itself may also be important for the loads, i.e. hydro-elastic effects and coupled effects between floater and mooring system. The wave- and wind-induced loads are highly connected to instantaneous wave elevation, relative motions and responses. Hence, the instantaneous position should be considered for updating the hydrodynamic and aerodynamic forces. Depending to the structure and its characteristics, the moving structure should use the accelerations and velocities at the instantaneous position. In some cases, the geometrical updating adds some nonlinear loading that can excite the natural frequencies of the structure. The relative velocity should be applied to the hydro loads and the updated wave acceleration at the instantaneous position is required for analysing some concepts. Definitely, dynamic response analysis is the base for design of offshore structures. In some cases, limit states analyses are based on combinations of individual dynamic analysis, i.e. consider a FLS which is based on accumulated damages. This shows the importance of performing correct dynamic analyses for offshore energy structures including the wave power, wind energy and hybrid energy devices.
This is a book chapter in Offshore Energy Structures: For Wind Power, Wave Energy and Hybrid Marine Platforms.