Response analysis and optimum configuration of a modular floating structure with flexible connectors

• Evaluation of internal loads of flexible connectors of a modular Pontoon type Floating Structure (PFS) based on “wet” hydroelastic analysis.
• Genetic algorithms based optimization for identifying PFS's optimum configuration (connectors’ rotational stiffness and grid type, i.e., number and layout of modules).
• Effect of connectors’ rotational stiffness and PFS's grid type on the connectors internal loads and on the hydroelastic response of PFS.
• Identification of an effective PFS configuration in terms of operational design requirements and structural integrity issues based on the variation of the connectors’ rotational stiffness in conjunction with the PFS's grid type.

In the present paper, a numerical analysis framework evaluating the connectors’ internal loads of a modular Pontoon type Floating Structure (PFS) as well as for identifying the PFS's optimum configuration under the action of regular waves is developed and presented. The PFS consists of flexible floating modules (pontoons) connected with flexible connectors in longitudinal and/or transverse directions. The numerical analysis framework includes: (a) a frequency domain ‘wet’ hydroelastic analysis for computing the PFS's ‘wet’ hydroelastic response and the connectors’ internal loads and (b) a genetic algorithms based optimization process for identifying the optimum configuration of the PFS considering predefined performance criteria. Different configurations of the PFS under the action of normal and oblique waves are taken into account, considering different number and layout of modules (grid type) and different values of the connectors’ rotational stiffness. The effect of the connector's rotational stiffness and the grid type of the PFS on the hydroelastic response and on the connectors’ internal loads is analyzed. For specific wave field characteristics, the optimum design configuration of the PFS is identified through the aforementioned optimization process in terms of performance criteria related to: (a) the vertical hydroelastic response at any predefined point of the deck of the PFS and (b) the internal loads of the PFS's connectors. The results obtained demonstrate the complex relationship between the internal loads of the connectors and the hydroelastic response of the examined PFS configurations with the connectors’ rotational stiffness and the PFS's grid type as well as with the excitation. They also demonstrate the applicability of the developed numerical analysis framework in order to properly direct the PFS's design towards a most preferable optimum configuration.