Method of designing and building a floating structure with natural period of 2 seconds or above, wherein the method comprises: to provide a rigid beam model with increased stiffness, in which natural periods are greatly reduced, by extracting excitation forces,
added mass and dampings via a panel model for a plurality of bodies or elements, into which the floating structure has been divided, to provide a flexible beam model with exact stiffness, by extracting excitation forces,
added mass and dampings via said panel model for said plurality of bodies, whereby dynamic
resonance at natural periods is captured in
time domain from the beam model, to find the dynamic
amplification factor by dividing the flexible beam model results on the rigid beam model results, thereby quantifying the dynamic
impact and obtaining dynamic amplification factors, distinguished in that the method of designing and building a floating structure with natural period of 2 seconds or above comprises: to add the dynamic contribution to the rigid beam model excitation forces, quantified by dynamic amplification factors for the bodies, thereby finding combined forces for the bodies, to model fatigue damages, using the combined forces, to finalize the designing process, to implement the design in building models, and to build the structure on a feasible construction
yard, or parts thereof on several feasible construction yards and transport and assemble said parts to the structure, wherein the resulting structure is a relatively slender structure compared to earlier method structures designed and built according to accepted codes and regulations.