固定型4脚構造物の波浪による過渡横振動の解析-海底地層の影響を考慮した海洋構造物の横振動(第4報)- [in Japanese] Analysis on Wave-Induced Transient Lateral Vibration of Four-leg Structure Supported by Seabed Layer -Analysis of lateral vibration of an offshore structure with consideration of the effect of seabed layer(4th Report)- [in Japanese]
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When analyzing the lateral vibration of an offshore structure supported by seabed layer, the effect of this layer must be taken into consideration. In the third report, a method has been proposed for reducing a four-leg offshore structure supported by seabed layer to a one-leg structure, and its natural frequency of lateral vibration has been analyzed theoretically. Furthermore, the validity of this method has been clarified by the model experiment. In this paper, the wave-induced resonance amplitude as well as bending stress in the leg of the offshore structure were analyzed theoretically and simulated numerically. The main results obtained are as follows : (1) With respect to the off-shore structure considered in this study, the first resonance of lateral vibration could be induced in it by practical wave-excitations. Once the resonance occurs, the leg's amplitude of the structure will increase almost linearly as the time elapses. (2) The maximum bending stress caused by the first-mode of lateral vibration always occurs at the top of the leg. (3) As soon as the vibration is fallen into the resonant state, the maximum bending stress in the leg increases almost linearly with the time, and then reaches the yield strength of the leg material in about 50 seconds, causing the failure of the structure. (4) Based upon the above results, the criteria for designing offshore structures are proposed from the viewpoint of evading the resonance phenomena caused by surface waves.
- Journal of MMIJ
Journal of MMIJ 114(6), 410-414, 1998-06-25
The Mining and Materials Processing Institute of Japan