Effectiveness and optimal design of gill cells in minimizing differential deflection in circular VLFS

Pontoon-type, very large floating structures (VLFS) carrying heavy loads in the central portion will undergo a “bowl-type” deflection shape. The resulting differential deflection may cause problems for smooth operation of equipment and compromise the structural integrity of the VLFS. In order to minimize this differential deflection, it is proposed that gill cells be introduced in the VLFS at appropriate locations. Gill cells are flooded compartments in VLFS by which the buoyancy forces are eliminated at their locations. This paper examines the effectiveness of the gill cells in a pontoon-type, circular VLFS in reducing the differential deflection as well as the stress-resultants with respect to the size and location of the gill cells. The optimal design of gill cells that minimizes the differential deflection and reduces the stress-resultants is also investigated.