考虑相关性的地下管网系统抗震可靠度分析方法

Seismic reliability analysis method of underground pipeline network considering correlation of variables

城市供水、供气、供热等地下管网是重要的生命线工程系统,由于管网中不同管线的结构属性、场地环境、地震动荷载等参数的相关性,管线结构抗震失效事件存在相关性。文章建立相关失效管网系统抗震可靠度问题的解析模型,给出随机变量相关系数在管线可靠度至管网系统可靠度的传递关系。利用基于Nataf变换和正交变换的一次二阶矩法,建立含相关随机变量的管线结构抗震可靠度解析模型;基于结构体系可靠度理论,求解管线结构失效相关系数;采用网络可靠度算法,计算相关失效管网系统节点连通可靠度。同时,给出基于相关随机变量抽样的Monte Carlo随机模拟解法。算例分析结果表明,在管段结构功能函数起控制作用的随机变量的强相关性,对管网系统可靠度影响较大;与传统的管线失效独立假定相比,管线失效事件的强相关性可使并联管网系统可靠度减小15%以上;管网系统拓扑结构的并联冗余性越高,管线失效相关性对系统可靠度的影响越大。

Urban water,gas and thermal pipeline networks are vital lifeline systems.Due to the correlation of those parameters such as structural properties of different pipelines,site conditions and seismic loads,the seismic failure events of pipelines in the network are correlated.In this work,an analytical model is proposed for the seismic reliability analysis of the pipeline network considering correlated failure of different pipelines,and the transfer of correlation coefficients of random variables from the reliability of individual pipeline to the reliability of the pipeline network is also presented.The analytical model of seismic reliability of pipeline structure with correlated random variables is developed using FORM based on Nataf transformation and orthogonal transformation.The correlation coefficients of pipeline failure events are obtained by the reliability theory of structural system.Furthermore,the network reliability method is utilized to evaluate the connectivity reliability of network systems considering correlated failures of pipelines.Moreover,the Monte Carlo simulation method for the pipeline network reliability evaluation considering correlated random variables is also presented.The case study results show that the strong correlation among the random variables that control the individual pipeline performance function has great influence on the reliability of pipeline network.Compared with the traditional assumption that the events of individual pipeline failure are independent,the strong correlation of pipeline failure events can reduce the reliability of the parallel pipeline network by more than 15%.For the parallel pipeline network,the higher the topology redundancy is,the greater the impact of correlated failure of pipelines on system reliability shall be.That is,the impact of pipeline failure correlation becomes more significant on the seismic reliability of the parallel pipeline network with higher topology redundancy.