考虑几何非线性的海底悬跨管道疲劳可靠性分析方法

Fatigue reliability analysis of submarine pipeline with free span considering geometrical nonlinearity

疲劳可靠性是海底悬跨管道安全性分析的一个重要组成部分。考虑海底悬跨管道的几何非线性特征,建立了悬跨管道疲劳可靠性分析方法。该方法结合模态分析,首先把系统隐式的非线性项转化为由模态坐标高次组合表示的显式非线性项,在此基础上引入虚拟激励法,建立结构在随机流力作用下的等效线性化系统,从而确定结构非线性随机响应,在此基础上进一步分析悬跨管道的疲劳可靠性。通过对某一海底管道的分析结果,表明该方法具有较好的计算精度和较快的计算速度。同时分析了不同悬跨长度对计算结果的影响,分析结果表明在管道悬跨长度较小时忽略几何非线性因素对结果影响很小,当悬跨长度较大时,忽略结构几何非线性的影响将会产生显著误差。

Fatigue reliability analysis is an important subject for safety assessment of a free span submarine pipeline. The objective of this paper is to present a new method for the fatigue reliability analysis of submarine pipelines with free span considering the geometrical nonlinearity. Using modal analysis, the implicit system is represented as an explicit nonlinear system whose nonlinear term is based on the combination of modal coordinates. Secondly, utilizing the pseudo-excitation method, the stochastic equivalent linear system is established. Based on the equivalent linear system, the responses of the pipeline can be obtained conveniently and the model for the fatigue reliability analysis is developed. The proposed method was used in the analysis of a suspended pipeline. The results show that the method has reasonable precision and high efficiency. Furthermore, the different spans of the submarine pipeline were analyzed. The result was little affected by the geometrical nonlinearity when the span is small. However, the geometrical nonlinearity has a significant influence when the span is long. And it can＇t be ignored, otherwise there will be a gross error.