Steel chains are usually used for mooring of various structures such as marker buoys for navigation, pontoons, and ship mooring buoys. However, the breakage of mooring chains has sometimes taken place. The main causes of the breakage are the abrasion between the chain links and the large impulsive tension acting on the chain. The authors have suggested to employ the "Elastic Chain", which has the property of elasticity. The elastic chain is manufactured by burying steel chain links within rubber column. The elastic chain for mooring can be expected to reduce the abrasion between the chain links and the intension of impulsive tension because of covered rubber material and its elasticity, respectively. However, the cost of the elastic chain is quite high compared with that of the normal chain. For the purpose of the cost reduction of mooring system, the authors have developed a simulation model to predict the motion of the mooring chain for a buoy and the impulsive tension acting on the chain. The model has adopted the lumped mass method for the simulation and can be applied for the normal and elastic chains. The validity of the model has been confirmed for the tension of the normal steel chain by the comparison with the experimental results by Hiraishi et al.(1995). The result of the computation for buoy mooring shows that the impulsive tension of the elastic chain is reduced up to 50 percent of that of the normal steel chain when a half of the mooring line is employed as the elastic chain and the other is as the normal chain. We have proposed economical design procedures of the mooring line.
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