Present study aims to investigate draft effects on hydro-elastic response of pontoon type VLFS(Very Large Floating Structure). A three dimensional higher-order boundary element method(HOBEM: Hong et al;1999, Choi, Hong and Choi; 1998) is extended to analyze elastic response of structures. Intensive numerical calculations were carried out for box type structure to investigate the draft effect on hydrodynamic forces on pontoon type VLFS. Main attention was paid to wave run-up along the waterline for various cases of draft scantling. It is found that the draft effects on the hydro-elastic response of pontoon type VLFS are important especially in short wave range and shallow water region.
Outstanding progresses have been achieved in field of hydroelastic analysis of VLFS during last five years. To name a few among them, Newman(1994), Yago(1996), Kashiwagi(1996, 1997, 1999), Maeda(1995, 1997), Takaki et al.(1996), Kim et al.(1996), Yoon et a1.(1997), Shin et al.(1999a, 1999b), Omatsu(1999) treated pontoon type and semi-submersible type structures in various aspects of view points; frequency and time domain analyses, inclusion of wave breakers, ...etc.. Most of works, however, were based on zero draft assumption for pontoon type structures presumably for the reason that zero draft approach is favorable mainly in the sense of numerical efficiency. If we imagine a few kilometer class pontoon type structures, main concern of frequency ranges will be inside wavelength to body length ratio(2/L) less than 0.1. In those frequency ranges the draft effects might not be negligible, if we pay attention to local flow around the structure such as wave run-up along the waterline which will be one of main considerations of freeboard design of the structure. In the present study, effect of draft changes on hydro-elastic response of pontoon type VLFS is investigated mainly focusing on local response, wave run-up along the waterline.
