Study On The Reliability Of Seismic Hydraulic Function Of Urban Water Distribution System

Urban water distribution system(WDS)provides water for people's daily life,production and fire protection,which is an important part of lifeline engineering.Previous earthquake damage shows that the earthquake will cause varying degrees of damage to buried pipelines,resulting in a decline in water distribution capacity,which not only affect people's daily life and production,but also weaken the fire rescue ability,and aggravate the secondary disasters occur such as post-quake conflagration.The reliability of seismic hydraulic function of WDS refers to the service performance of the pipe network under the possible seismic intensity.It is usually quantified by the flow or water pressure of the pipe network node under the condition of seismic damage.In the face of frequent earthquake disaster,research on the seismic reliability function of urban WDS,can not only make the reconstruction work more pertinence,but also helps to optimize seismic design of WDS,which has important research significance and practical value.Based on this,this paper carried out the following research,and obtained the relevant research results and conclusions are as follows:(1)Based on the previous research results,we summarized the seismic damage characteristics and reliability research methods of urban WDS.Firstly,the earthquake damage of WDS,the form of pipeline breakage and the influence factor are summarized and analyzed.Then,after introducing and comparing the two methods of research on seismic behavior of urban WDS,as theoretical method and empirical method,we found that empirical method is much more simple.Finally,the first-order two-moment method and Monte Carlo method are introduced,and the applicability of the two methods is analyzed.(2)Considering of the fact that domestic scholars have not reported the research and application of GIRAFFE software,this paper studies the reliability evaluation method of Seismic reliability evaluation method of urban WDS based on GIRAFFE software.First of all,taking the software stochastic simulation process as the main line,this paper expounds the analysis principle of the seismic loss pipe network,and points out the shortcomings of the software in the hydraulic analysis of the earthquake damage pipe network.Then,the software is used to evaluate the reliability of a city's WDS of the earthquake-prone areas under the seismic intensity of VIII and IX.(3)We propose a stochastic simulation method for the reliability evaluation of urban WDS.Firstly,the seismic damage scenarios are generated using Monte Carlo simulation.The pipe working state is determined by using the Poisson random number and the uniform random number,and the leakage area of the pipeline is ascertained by using logarithmic normal random number.Then,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.At last,based on the ratio of node flow statistic mean and normal node flow in earthquake damage scene as Reliability index,the performance of a city's WDS under the seismic intensity of VIII and IX is evaluated.This result is compared with the evaluation results of applying GIRAFFE.Therefore,the feasibility of the proposed method is verified.