城市供水管网抗震可靠性评估的随机模拟方法

在进行管网抗震可靠性评估时,现有方法大多采用相同方式进行管道的渗漏与爆管水力模拟,这会导致管网水力模拟及可靠性评估结果的不准确。考虑到地震时管道破损具有很大的随机性,对城市供水管网抗震可靠性评估的随机模拟方法进行研究。应用蒙特卡洛模拟产生管网震损场景,用泊松随机数与均匀随机数判定管道工作状态,用正态随机数确定管道渗漏系数;利用EPANET软件中喷嘴及管道关闭功能实现管道渗漏及爆管等效模拟,提出将长管道分段并应用"分步迭代"法求解低压管网水力方程,提高震损管网水力模拟精度。以震损场景下节点流量统计平均值与正常时节点流量的比值作为可靠度指标,分别采用所提出算法及GIRAFFE软件对云南某古镇供水管网在VIII、IV烈度时抗震可靠性进行评估,评估结果证明了所提出算法的可行性。评估结果还表明,除地震烈度外,管网本身水力条件对供水可靠性影响较大,管网末端、支管服务区域及地势较高区域供水可靠性远低于干管服务区。

Stochastic simulation method for seismic reliability assessment of urban water distribution system

When evaluating the seismic reliability of urban WDSs,most of traditional methods use the same approach to simulate the leakage and burst,which leads to inaccurate results of simulation and reliability evaluation.Considering pipe damages due to earthquake are random,this paper proposed a stochastic simulation method for seismic reliability assessment of WDSs.Specifically,the seismic damage scenarios are generated using Monte Carlo simulation,in which Poisson and uniform random number are used for determining pipe working status,and normal random numbers are used for pipe leakage coefficient generation.Pipe leakage and burst are simulated based on the emitter and pipe close function in EPANET.To improve hydraulic simulation accuracy of the damaged WDSs,the long pipes are segmented and "two-step iteration" method is introduced to solve the network in low pressure condition.The ratio of the statistical average values to normal values of nodal demand in seismic damage scenarios is used as reliability index.The proposed algorithm and GIRAFFE software are used to evaluate the performance of WDSs of an ancient town in Yunnan under Ⅷ and Ⅳ seismic intensity,and the feasibility of the proposed algorithm is demonstrated by analyzing and comparing the evaluating results.Evaluation results indicate that,in addition to seismic intensity factor,the hydraulic condition has great influence on the seismic reliability of WDS.Under the same seismic intensity,the water supply reliability for areas located in high terrain or far from water resource is considerably lower than that of areas closed to the water source with main pipe being serviced.