Abstract：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 correlatedIn 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.
