The hydroelastic response of very large floating structure suppoted by footing-columns (2nd report)

Abstract

A Very Large Floating Structure (VLFS) is expected as a new utilization of the ocean space. Rigidity of VLFS is, however, relatively small, so that an hydroelastic response of VLFS in waves should be considered. Many researchers studied on the elastic response of a pontoon type VLFS, in addition, on that of column support type VLFS. The VLFS supported by columns shows the smaller elastic response than that of the pontoon type VLFS. In the 1st report of this paper, we have discussed about hydrodynamic responses of a column with footing which has a wave-free frequency on wave exciting force and also examined the hydroelastic responses of a VLFS supported by a large number of the columns in regular waves.In this paper, we investigate on the charcteristics of hydroelastic behaviors of a VLFS supported by a large number of footing-columns which have two wave-free frequencies. And then, we disccuse about the hydroelastic behaviors of a VLFS in irregular seas based on spectral analyses. Furthermore we compare the hydroelastic responses of VLFSs among supported by columns without wave-free frequency, supported by columns with one wave-free frequency and supported by columns with two wave-free frequencies. In the analyses, the hydrodynamic forces of the single column are calculated by using 3-dimensional source sink method, and the hydrodynamic characteristics of VLFS are obtained by using hydro interaction theory.