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UBC Theses and Dissertations

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UBC Theses and Dissertations

Water distribution system reliability under pipe failure conditions : advanced multiple states/aspects analyses Gheisi, Alireza


Every water distribution system (WDS) fails (partially or completely) at some point(s) during its lifetime. Measuring the reliability of a system under various failure conditions has been recognized as a highly controversial issue in the field of WDS analysis. Accordingly, numerous techniques have been developed to estimate WDS reliability. This research provided an in-depth review of the relevant literature and developed advanced techniques for reliability analysis. The research organized and classified the available techniques into three major categories and discussed which technique should be used depending upon the type of a failure (mechanical failure, hydraulic failure, and water quality failure). Previous studies have focused on WDS reliability when pipes fail individually. The current research developed an advanced technique to determine the reliability of a WDS experiencing different degrees of simultaneous pipe failure (i.e., higher-states reliability analysis). The technique was applied to two case studies including a hypothetical as well as an in-practice WDSs. Results demonstrated that a system might be able to achieve a higher level of reliability if more realistic expectations of simultaneous failure were assumed. Studying various reliability measures, this dissertation revealed statistical flow entropy had stronger correlation with higher states of reliability and was a better surrogate measure. Using multiple criteria decision analysis (MCDA), an advanced technique of multiple states reliability analysis was developed and applied to rank a set of WDS layouts (alternatives) using various states of reliabilities (criteria). The analysis revealed that the higher-states reliabilities should have more contribution in the decision-making process. A comprehensive reliability analysis should consider the system’s responses to various states of failure. This research employed the techniques of quadrant and octant analyses to study the response of a hypothetical WDS to various simultaneous failures in two or three aspects. It was found that evaluating the reliability in one aspect without incorporating other aspects would lead to misleading results. The advanced technique of multiple aspects/multiple states reliability analysis was developed using MCDA. Multiple aspects/multiple states reliability analysis was employed to rank the WDS’s layouts. Results revealed that multiple aspects/multiple states reliability analyses would assure more reliable operation of a WDS.

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