Seismic Performance Assessment And Preformance-based Design Of Water Distribution System

Urban water supply system consists of raw water intake facilities, aqueducts,water treatment plant, pump stations, water distribution pipelines and user terminals.All of these parts can be divided into two categories: pipelines and station facilities.When surfing earthquake attacks, the procedure of disaster effects on water supplysystem spread as follows: pipeline or station facilities subjected to structural damagesfirstly, water supply functions, including both pressures and the amount of watersatisfied, weakened or totally loss then, which finally result in the performance of thewater supply system can’t meet the requirement of post-earthquake relief, recoveryand normal water demand during different time period after the earthquake. The aimof earthquake resistance and disaster mitigation of urban water lifelines includes theenhancement on seismic security of the facilities structures and the improvement onseismic performance of the entire system. Therefore, the seismic research and designof urban water supply system can be divided into two parts:(i) structural capacity ofpipelines and station facilities for the “element” level, and (ii) system performance ofwater distribution system for the “system” level. This dissertation has facoued on thesecond part which is based on the precondition that seismic capacities of structuralelements are determined.The research objects of this dissertation include seismic performance assessmentmodel and seismic design method for water distribution system (WDS) correspondingto the “system” level classified above. The WDS is regarded as a part of water supplysystem and consists of distribution pipelines and user terminals and pipelines. Theworks of this dissertation mainly focus on how to assess the WDS seismicperformance efficiently when the structural seismic capacity of facilities is known,and how to process the performance-based seismic design and renovation of WDS.The main efforts and conclusions are given as follows.I. Efficient Algorithm for Network Reliability Evaluation.i. Perfection and improvement for directly disjoint algorithm (DDA) usingbounds. This algorithm can obtain disjoint minimal path and disjoint minimal cutwithout prior enumeration of minimal path or minimal cut, and can get exact solutionof simple networks and approximation of large networks with real-time accumulationof disjoint minimal paths and cuts. Numerical example analysis showed that DDA ismore suitable for networks with elements in state of lower reliability.ii. Stochastic simulation model using importance sampling for lifeline networksseismic reliability evaluation. The importance sampling function, generated by anadaptive sampling method, was used to generate element state of each sample, which can increase the appearance chance of system failure. Methods to transform networkswith imperfect nodes to equivalent networks with perfect nodes and estimate theelement reliability sensitivity by Monte Carlo simulation were also proposed.II. Accurate&Suitable Model for Earthquake Damaged WDS HydraulicAnalysis.i. Comparative study on hydraulic simulation model of earthquake damagedpipelines. The outflow models of pipeline damages (leaks and breaks) induced byearthquake is established by theorems of Fluid Mechanics. Comparisons on outflowmodels of pipeline damages and topology models of damaged pipeline networks wereaccomplished by flow pattern analysis, which illustrated the suitability and reasons ofdifferentias of existing models.ii. Pressure-dependent Analysis of earthquake damaged WDS (ED-WDS). Thepressure-dependent demand (PDD) relationship was utilized in the process ofpressure-deficient hydraulic simulation of ED-WDS to avoid node negative pressure.A backtracking and line search procedure was utilized to control the iteration step ofpipeline network nonlinear equations, which ensure the global convergence of thehydraulic simulation.III. Seismic Performance-based Design Method for WDSi. Seismic performance-based design considering integrate importance of Users.Users importance assessment index system was established by considering the normaloperation function, post-earthquake relief function and network topology. Seismicperformance-cost curve of pipeline structure was analyzed according to the relationsamong cost factor, displacement of pipe segment joints and seismic reliability. Thedesign parameters include network topology and seismic capacity of pipelinestructures, and can be assigned by optimization algorithms.ii. Searching space reduction method for WDS seismic design optimization. Theselection of WDS seismic design parameters is a combinatorial optimization problem.A two-stage searching space reduction strategy for WDS seismic design using GAwas proposed. In the first stage, the initial population is generated by degreeconstrained connected graph, which narrowed the optimization search space at thebeginning of GA. A genetic individual repair strategy was proposed for individualsviolate constraints in the evolutionary process.