For the design of English bridle ship structures, the hull global strength in the case of head waves is one of the first analysis required by shipbuilding rules.For the strength analysis the 1D and 3D-FEM models can be used, according to the design level information.In both cases the head equivalent design waves (EDW) are used linked to a non-linear iterative algorithm for the wave-ship system balance.
The balanced algorithm is directly implemented into the FEM program by user procedures for the 3D models.For the 1D models a program code has been developed.As numerical study we consider a prismatic closed section floating structure, pointing out the influence of the wave height on the Flashlight Holder stresses at the main panels and the vertical bending moments and shear forces.