SUMMARY NOTES ON MOORING DYNAMICS SEMINAR 



Michel K. Ochi 



Comments and remarks on some important subjects associated with mooring 

 dynamics are sunnnarized as follows: 



1. Waves for Mooring System Design 



(a) Since a mooring system encounters a variety of wave conditions even though 

 the sea severity (significant wave height) are the same, and since the system 

 responds strongly to low frequency components of wave spectra, it is highly 

 recommended to use a series (family) of wave spectra consisting of several 

 members for any specified sea severity. 



(b) It is recommended to use the fetch-limited wave spectra for evaluating 

 responses of a mooring system located in the area where the fetch length 



has to be considered. The shapes of the fetch-limited wave spectra are signi- 

 ficantly different from those for open sea spectra. 



(c) For mooring in coastal zones including the continental shelf, the wave 

 spectra should be modified taking into account the effect of water depth on 

 spectra. This can be done by developing a computer program to modify the 

 wave spectra from deep to shallow water area. 



(d) The estimation of extreme values, such as the maximum tension of the mooring 

 lines, etc., has to be precise based on extreme value statistics. The method 

 of evaluating the maximum tension loads given in the available literatures 

 appears to be inadequate. 



(e) It is recommended to consider the directional wave spectra for more accurate 

 prediction of responses of a mooring system in a seaway although the computa- 

 tion would be extremely complicated. 



2. Nonlinear Behavior of Mooring System 



It is apparent that the nonlinear dynamic response has to be considered 

 for a mooring system in a seaway. Many nonlinear dynamic response problems 



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