波流联合作用下海底管跨疲劳失效的分析

针对由涡激振动引发的海底管跨疲劳失效，提出管跨非线性涡激振动失效可靠性分析方法，引入波浪和海流对管跨的联合作用以及管跨所受轴力，并考虑管跨海底土壤支撑端的实际工况，建立了管跨段的垂向非线性振动方程及其边界条件．通过模态分析，求得振动方程的固有振型，并以此为基础，推导和建立方程解的关于时间域的微分方程组，运用时频分析方法，由波浪谱推得的波、流力谱作为振动方程的输入谱，计算得到相应的输出谱，进而确定位移和应变等各种响应随机过程的概率分布，结合可靠性理论确定管跨的疲劳失效概率．最后，通过实例的计算与分析，确定几个重要参数对管跨疲劳失效的影响程度．

Fatigue Invalidation Analyses of Submarine Pipeline Span Subjected to Wave and Current

In view of the fatigue invalidation of submarine pipeline span caused by vortex-induced vibration, the reliability analysis method of nonlinear vortex-induced vibration invalidation of pipeline span is proposed. Considering axial force and influence of wave and sea current on the spanning pipeline span, the perpendicular nonlinear vibration equation and its boundary conditions are set up according to the factual submarine soil supports for pipeline. Based on inherent modes determined from the equation of motion describing free vibrations, the differential equations about time domain of the equation solution are deduced and established. Using time and frequency domain approach, the wave and sea current force spectrum is derived from wave spectrum and taken as the input spectrum to deduce the output spectrum, and the probability distribution of displacement and strain are obtained. So the fatigue invalidation probability of pipeline span is figured out according to reliability theory. Finally, by the calculation and analysis of an example, the effect degree of some important factors on the fatigue invalidation of pipeline span is obtained.