Abstract
In Japan, large main ports are located in the area where sea conditions are good and they are near the big cities. But recently it is pointed out that this area is not necessarily desirable as harbours in all aspects. The Ministry of Transport is planning to build new ports outside bay. But the outside ports have serious natural conditions than inside ones. Then we simulate one-year workabilities by using the harbour tranquility and a moored ship motion. We introduced the "ASYMMETRICAL AMPLIFICATION FUNCTION", which explains easily a phenomenon of Subharmonic Motion. The obtained results can be summarized as follows : (1) When we simulate one-year workability of harbours, we have to consider the wave height in a harbour, ship entry into port, and moored ship motions. (2) The maximum value of the amplitude of Subharmonic Motion X_<max> can be expressed as the sum of the maximum value of amplitude in case of free vibration X'_<max> and the amplitude in case of symmetrical mooring ζ_<max>. (3) We consider the Subharmonic Motion. Then we introduce AS (T) : "ASYMMETRICAL AMPLIFICATION FUNCTION" which can explain this complicated phenomenon easily. The value of AS (T) increase rapidly from about 40 of spring constant ratio. AS (T) is 1 at harbours inside bay as the incident wave period is short, but it becomes several times as the wave period is long at harbours outside bay.
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