海洋構造物の事故と安全性

後藤政志，芝浦工業大学工学部
[ Link to jstage.jst.go.jp ]

Overview – An offshore structure is not able to avoid the encounter of the severe storm always, because of the characteristic of the purpose which is to stay at the specified sea area for the operation. This paper describes the design method for typical offshore structure
briefly, then explains the some accidents of the offshore drilling rig, and finally presents the fundamental idea about the safety issue based on the investigation of the specific technical problems related to the causes of accidents.
　Many rigs for Arab, Mexico, Canada and North sea were constructed at Japanese shipbuilding yards between the 1970’s and the 1980’s followings the world wide rig construction boom. As Japan has a few rigs and a little information about the accidents of the offshore drilling rigs, according to the Lloyd’s lists and some reports related accidents, the accidents of the offshore structures occur often as compared with ships and the scale of the accidents is often beggar than normal ship. Norwegian semi submersible accommodation platform “Alexander L. Kielland” collapsed and capsized due to fatigue failure at the weld part of the brace at
North sea oil field in March 1980.
　123 lost their lives by this accident. Also jack up rig “Dan Prince” sank in Araskan waters during wet towing in October 1980. These impact the later design philosophy to establish the residual stability requirements and structural redundancy evaluation requirement for the offshore structures.