基于非线性理论的海底管跨涡激共振可靠性研究

海底管跨的涡激振动是引发管跨共振失效的主要因素．为此，考虑波浪水质点与海底管线管跨段振动间的相对运动速度以及波浪和海流的联合作用，对传统的波浪载荷计算方法进行了改进，引入了波浪激励载荷中的二阶平方阻尼项，从而建立了海底管跨的非线性涡激振动方程．同时，基于非线性振动特性，将倍频共振和亚频共振的概念引入管跨的涡激共振失效分析方法中，建立了相应的极限状态方程和管跨涡激共振长度预测公式，在此基础上提出了管跨的涡激共振失效可靠性分析方法，并通过算例验证得出海底管跨倍频涡激共振长度小于基频共振长度和亚频共振长度．建议在预测管跨的共振长度时，考虑管跨发生倍频共振时的长度，以保证其可靠性．

Reliability Research on Vortex Induced Resonance of Submarine Pipeline Span Based on Nonlinear Theory

Vortex induced vibration of submarine pipeline span is the major factor of resonance invalidation of pipeline.Therefore, both relative motion of water particle of wave and vibration of pipeline span and co-efficiencies of wave and sea current are considered, and the traditional calculation method of wave force is improved. Due to the introduction of second-order square damp term in wave force, the nonlinear vortex induced vibration equations of pipeline span are set up. Meanwhile, based on the nonlinear vibration characteristics, multiple frequency resonance and fractional resonance are introduced into the analysis method of vortex induced resonance invalidation of pipeline span. According to the above method, the corresponding limit status equations and evaluation formulas of the span lengths at the charge of vortex induced resonance are presented, which are applied to carry out reliability analysis on vortex induced resonance invalidation of span. Besides, the submarine pipelines span lengths at the charge of multiple frequency vortex induced resonance are less than the natural frequency and fractional frequency status is validated by example.Consequently the pipelines span lengths at the charge of multiple frequency vortex induced resonance are recommended for evaluation.