Recent growth in LNG market has led dramatic increase in new buildings of LNG carriers and several large LNG carriers are now being constructed by shipbuilders in Korea. Large size LNG carriers have brought keen concerns on the issues regarding safety of cargo containment systems and sloshing impact load which is the critical source of loads on the membrane type containment systems. Up to the present, the best way to properly assess sloshing impact pressures on surrounding walls is a model testing for wide-ranged excitation conditions. These impact pressures obtained from model tests sometimes need to be interpreted to full-scale values and in the near future this necessity will be strengthened for more rigorous and direct safety assessment of LNG cargo containment system. In this paper, a basic experimental study is carried out with two different sized, 2-dimensional identically shaped model tanks excited in simple translational motions. Scales of two model tanks are selected as 1/50 and 1/25 in order to investigate the impact pressure characteristics according to the model tank sizes. Relationships between pressures of different sized model tanks are investigated for three filling heights and two excitation amplitudes per each filling height. For measuring impact pressures, about 15 pressure sensors are used on various locations of the model tanks and in order to compare the results from two different sized tanks, statistical values are used. All tests are carried out on the hexa-pod motion platform at Pusan National University, Korea.
Recently the size of the LNG carriers is increased and the first vessel of 210,000m3 LNG carriers which are being built in Korea was delivered to the ship owner successfully. The larger LNG carriers with about 260,000m3 cargo volume are now being constructed also in Korea.
