Reliability Analysis of Mooring System under Stormy Weather
Yoshimi Nagao, Katsuhiko KURODA, Kinzo INOUE · The Journal of Japan Institute of Navigation · 1984
Two models are proposed for evaluating the safety level of a ship moored at a berth inside a harbour under stormy weather such as typhoon. One is based on the first passage problem of a stochastic process, and the other is based on the extremal probability distribution. Both methods can evaluate a probability that the random tensional response of a mooring rope to random external forces by wave, wind and high-tide exceeds its strength. According to the computational results of both methods, followings are concluded; (1) The first passage failure model should be used when the average value of the induced rope tension is 40% or more of the rope strength. (2) The extremal probability model has no practical difficulty in case that the average value of the induced rope tension is under 40% of the rope strength. Proposed models give us many information regarding with the safety level of the mooring system. Therefore they are useful for decision making on the engineering planning and design of the mooring system under stormy weather.