波致立管疲劳损伤计算方法研究

On calculation method for wave-induced fatigue damage of riser

针对波浪作用下平台运动引起的立管疲劳损伤,进行完整的频域计算方法研究。首先采用势流理论对平台的运动响应进行分析,求得平台的运动频响函数;接着采用有限元法对立管的应力响应进行分析,求得立管的应力频响函数;最后,结合立管材料的S-N曲线,采用谱分析方法对四种不同海况下波致立管振动引起的疲劳损伤进行分析,获得损伤沿立管轴线方向的分布曲线。研究结果表明:波致立管振动疲劳损伤与有义波高密切相关,疲劳损伤值随着波高的增加成指数次方增长;立管的最大疲劳损伤值通常出现在立管的边界区域。

This paper carries out the complete numerical investigation of the fatigue damage of a riser due to the wave-induced motion of platform in the frequency domain. Firstly, it calculates the motion responses of the platform by potential lfow theory, and obtains its motion frequency response function. Then, it analyzes the stress responses of a riser by ifnite element method, and obtains its stress frequency response function. Finally, it carries out the spectral analysis of the fatigue damage of the riser due to the wave-induced vibration under the four different sea states combined with S-N curve of the riser material, and draws out the distribution curve of the damage along axis of the riser. The results show that the wave-induced fatigue damage is closely related to the signiifcance wave height and increases exponentially with the increasing wave height, and the maximum wave-induced fatigue damage along the riser usually appears near the boundary regions of the riser.