ジャッキアップタイプ・オイルリグの実機振動実験

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Recently shipbuilders in Japan have designed and constructed many jack-up oil rigs, and accordingly quite a few investigation have been performed on the static and dynamic characteristics of jack-up oil rig. ' The authors have been systematically studying not only the global vibration of oil rig, but also the local vibration of leg by theoretical and experimental approach. In the previous paper, the authors mostly discussed the calculation technique and pointed out the spring effect of the sea bed is very important factor for calculation of natural vibration of oil rig. This paper deals with the vibration tests of the actual jack-up oil rig constructed during two years. At these tests oil rigs were excited by wire cutting method" to measure the lower natural frequency and logarithmic decrement. At the same time the vibration of leg to wind excitation was also measured to catch its natural frequency. Main conclusions are as follows : (1) "Wire cutting method" is very useful for measuring natural frequency and logarithmic decrement of oil rig. (2) The measured lower natural frequencies are approximately proportional to h^lt:-3/2> (h : platform height) and W^<-1/2>(W : platform weight). (3) Logarithmic decrement shows from 0.2 to 0.3, which is larger than ship's. (4) The first and the second mode of the leg are governed by bending and torsional deformation, respectively. The former natural frequencies are approximately proportional to l-2 (1 : leg length) and l^<-1>, respectively.
社団法人日本船舶海洋工学会の論文

ジャッキアップタイプ・オイルリグの実機振動実験

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