海洋平台结构系统的冰激疲劳可靠性分析

ICE-INDUCED FATIGUE RELIABILITY ANALYSIS FOR STRUCTURE SYSTEM OF OFFSHORE PLATFORMS

提出一种冰激疲劳损伤简化计算方法,用于计算冰力作用下平台管节点的疲劳损伤,并根据该方法分析平台构件和整体的疲劳可靠性。该方法用两个指数函数拟合平台和海冰相互作用时疲劳应力和应力循环次数与海冰厚度、速度的关系,具有较高的拟合精度,而且给出基于S—N曲线的疲劳损伤计算公式,从而使疲劳损伤计算得到很大简化。在此基础上,给出平台构件可靠性和整体可靠性的计算方法,并通过提出冰载荷作用下海洋平台整体疲劳失效的简化判断依据,简化平台整体疲劳可靠性计算过程。同时基于断裂力学的Paris公式,建立冰载荷作用下构件疲劳裂纹扩展的可靠性模型,当平台被检测出有裂纹时,可以使用该模型对构件和平台整体进行可靠性分析。对冰激动力响应不太严重的平台,可以用文中提出的方法进行疲劳可靠性分析。

A simplified assessment method of fatigue damage was presented, which can be used to calculate the fatigue damage of tubular joints of platform under ice-load, and it was used to analyze the reliability of components and system of platforms. Two exponential functions were used to reflect the relationship between fatigue stress and number of stress cycles to ice thickness and ice velocity while platform and ice interacts. The fitting precision of this method was relatively high, and the expression of fatigue damage, which based on the S- N curve, was obtained, and the calculation of fatigue damage of platform was simplified. The calculated method of reliability of component and whole system of the platform was presented, and a simplified criterion of fatigue failure of the platform was suggested, the calculated process of reliability of platform system was predigested. The reliability model of fatigue crack growth was built, which based on the Paris formula of fracture mechanics. This model can be used to analyze the components and entire platform when there were cracks in the components. The fatigue design method in this paper can be applied in fatigue assessment of the offshore platforms whose ice-iuduced dynamic effect is not serious.