Deepwater composite catenary riser optimization design based on the multi-island genetic algorithm

Abstract

In deepwater resource exploitation, fiber reinforced composite materials offer several advantages, such as high specific strength, high corrosion resistance, and high fatigue resistance. However, application of composites to offshore risers also introduces a large number of design variables and constraints in structural design due to the anisotropy of composite materials and multi-layer structures. A methodology was presented for optimization design of composite catenary risers based on the global-local analysis, with the consideration of design and safety requirements. First, the classical lamination theory was used to obtain the equivalent mechanical properties of the laminated tube, and next an equivalent structural model was built and a global dynamic analysis of it under the load of ocean environment was performed. Finally, the optimization procedure was applied by taking the thickness and winding angle of layers as design variables and the strength and buckling load of different dangerous cross sections as constraints under various working conditions. The multi-island genetic algorithm was used as the optimal strategy; the optimized composite catenary riser meets the strength and stiffness design requirements and saves a certain amount of composite materials. Research shows that the proposed methodology of composite catenary riser optimization design based on multi-island genetic algorithm is feasible.