ABSTRACT

Ocean space utilization using VLFS(Very Large Floating Structures) can provide environmental impact free space by allowing sea water to flow freely below the floating structure. Use of Pontoon type VLFS for that purpose necessitates the construction of breakwaters for reduction of wave effects. Therefore, in order to maximize advantage of environmental impact free structure, the breakwater should allow water to flow through it. In this paper hydro-elastic response of a pontoon type structure is analyzed considering breakwaters which allow water flow through its opening at bottom of the structure. Mode superposition technique is used for solving equation of flexible body while interactions between the pontoon and breakwaters is considered based on the generalized mode concept. The effects of various combinations of breakwaters are investigated.

INTRODUCTION

Pontoon-type VLFS has been widely studied for various conditions; without and with breakwater, airplane landing and take-off, and so on. The main assumption of using pontoon-type VLFS is the installation of breakwater together in order to reduce wave loads on the VLFS. Conventional type breakwater seems to give best wave-breaking performance but it also cuts off water flow around the VLFS. Therefore use of conventional type breakwater cancels typical merit of VLFS; free of environmental impact. Furthermore, costs for construction of breakwater by reclamation may govern the total costs of constructing VLFS as the installation depth increases. So, the use of other-type breakwaters which allow free water flows through them is essential not only for the sake of development of environment friendly space on the sea but also from an economic point of view. Most studies on effects of breakwaters were for conventional bottom mounted breakwaters, and potential matching techniques were used between inside and outside regions of the breakwater(Lee, 2001, Nagata et al., 1999, Ohmatsu, 1999).

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