This paper proposes maximum allowable wave heights for cargo handling determined by numerical simulations of ship motions for general cargo ships, grain carriers, ore carriers, container ships and car ferries. Also studied is how maximum allowable wave height relates to the spectrum of long-period waves, the characteristics of mooring ropes and wave directions. The proposed maximum allowable wave height is used to calculate the wharf operation efficiency of ports and harbors that face open seas.
Cargos handling problems, breakages of mooring ropes and fender damages have been reported at several ports in Japan and overseas that face the open sea (Shiraishi, 1998). These problems are attributed mainly to the large motions of moored ships caused by swells and long-period waves. The author's previous study defined the wharf operation efficiency as the percentage of hours that wave conditions permit cargo handling (Shiraishi et al., 2006). "Hours that wave conditions permit cargo handling" is defined as hours during which the wave height at the wharf is lower than the maximum allowable for cargo handling for specific types and sizes of ship. The maximum allowable wave height for cargo handling is derived from the motions of ships moored to quay walls at a port. The motions of a ship are assessed for general wave components (such as wind waves and swells) and for long-period waves. Determination of weather cargo handling is possible for a given wave condition can be done by comparing the motion of the ship under the wave condition and the allowable ship motion for cargo handling. This is called "detailed analysis of wharf operation efficiency," and it is more accurate than the simpler method that mentioned below, although it poses higher calculation load because ship motions need to be calculated for every wave conditions. The simpler "standard analysis of wharf operation efficiency" is usually used in calculating the wharf operation efficiency.
