Cyclically Buckling/Plastic Collapse Behavior of Deck Beam-Column Obtained by Fluid-Structure Interaction Analysis for Floating Structure in Waves

Fluid-structure interaction analysis applying ICFD solver incorporated in ANSYS LS-DYNA is applied to rigid motion of a floating box and hydro-elastic motion of a slender floating beam in waves, and the fundamental validity is confirmed comparing with the past test results and theoretical solutions. A structure with a slender beam-column in the deck is assumed to be floated in waves. The cyclically buckling/plastic collapse behavior of the deck and the overall bending response of the whole structure are examined through the fluid-structure interaction analysis varying the slenderness ratio of the deck. As a result, it is found that both the tensile and compressive load-carrying capacities of the deck are reduced with an increase in the number of wave encounters and this tendency becomes remarkable in the slenderer deck. The reduction of the compressive capacity especially depends on the residual deflection of the buckled deck. Regarding the bending moment acted on the whole structure, the maximum hogging moment is obtained just when the tensile axial force of the deck attains the peak. However, the sagging moment continuously increases even after the compressive force attains the peak because the intact bottom part can be subjected to a further moment. The overall bending deformation of the whole structure is influenced by the reduction of the load-carrying capacity of the deck after the peak.