A Method for Structural Design of Pontoon Type VLFS Based on Collapse Behavior and Reliability Analysis

This paper deals with a simplified method for the preliminary design of pontoon-type very large floating structures (VLFS), which are supposed floating airport, based on collapse behavior and reliability analysis in irregular waves. Firstly, a simplified estimation method is presented for the probabilistic load effect model of VLFS under irregular sea-state conditions. Next, limit state conditions are shortly presented for the buckling and ultimate collapse strength of stiffened plates under combined compression, shear and lateral pressure in the deck, bulkhead and bottom parts of VLFS, especially, by using a simplified estimation formula. Then, the validity is shown by non-linear finite element method. Finally, dominant limit state modes of 5,000m-class VLFS under combined loads with bending moment, shear force and lateral pressure are obtained by applying the above methods. Then, the features of the collapse behavior and reliability level are investigated by using above calculation results. Effects of design parameters such as yield stress, plate thickness, stiffener and bulkhead space are also investigated using sensitivity analysis.