Optimal layout of gill cells for very large floating structures

Abstract

This paper is concerned with the optimal layout of gill cells for minimizing the differential deflection of a very large floating structure under a non-uniform load distribution over the surface of the structure. Gill cells are compartments in the floating structure where the bottom surface is perforated to allow water to flow freely in and out. At the locations of these gill cells, the buoyancy forces are eliminated. When placed appropriately, these gill cells are very cost effective in minimizing the differential deflection of the loaded structure. So the optimal layout of the gill cells is a very important design consideration. In this paper, the modeling of a very large floating structure with gill cells is developed and a computational method based on genetic algorithms for seeking the locations of a given number of gill cells is presented. The model and optimization technique are demonstrated on a floating structure which carries a heavy load in its central portion of the structure. Resulting from the non-uniform heavy load on the structure, the differential deflection may cause operational problems for equipments which are sensitive to tilting. Using gill cells that are positioned optimally, it will be shown that the differential deflection can be considerably minimized. Copyright ©2007 by ASME.