EVALUATION OF EFFECTIVE WORKING DAYS CONSIDERING MOORED SHIP MOTION IN POHANG NEW HARBOR

Abstract

This study proposes an estimation method for allowable wave heights for ship loading and unloading and evaluation of effective working days, considering moored ship motion that is affected by ship sizes, mooring conditions, and wave periods and directions. The method's validity was examined with wave field data at pier 8th in Pohang New Harbor. The wave field data, obtained when downtimes had occurred, indicated wave heights of 0.10-0.75 m and wave periods of 7-13 s for ship sizes ranging between 800-35,000 ton in weight. On the other hand, the estimated results for allowable wave heights for ship loading and unloading using this method yielded wave heights of 0.19-0.50 m and wave periods of 8-12 s for ship sizes of 5,000, 10,000 and 30,000 ton in weight. Thus, this method reproduced well the field data responses of ships of various sizes and at different wave periods. But the allowable wave heights proposed by Korea's technical standard are did not respond to various the ship sizes and wave periods. And the results of this method tended to decrease in 16-62 percent when have considered long wave, and it is decreased in 0-46 percent when did not consider long wave than Korea's technical standards in case of the ship sizes of 5,000-30,000 ton, wave period of 12 s and wave angle of 75 degree. The allowable wave heights for ship loading and unloading proposed by Korea's technical standards have indicated that overestimated for ships smaller than 10,000 ton in weight. On the other hand, the percentage rate of effective working days accounting for ship motion at pier 8th in Pohang New Harbor was 6.5 percent less compared to the corresponding results that did not consider ship motion.