Reliability Analysis of Water Distribution Systems Using Physical Probabilistic Pipe Failure Method

Water distribution systems (WDSs) are among the most essential infrastructure systems for the sustenance of societies. Therefore, their continued reliability is of utmost importance. However, the reliability of WDSs decreases over time due to aging and deterioration of components, especially pipelines. Metallic pipes are subject to external and internal corrosion overtime, which can significantly affect their mechanical strength and hydraulic performance and, consequently, WDS reliability. Existing research on system reliability is typically based on statistical failure prediction of pipelines, which, however, typically assumes a constant failure rate, thereby ignoring time-dependent strength deterioration due to corrosion. This paper proposes a framework for modeling the time-dependent reliability of WDSs with cast iron pipes considering both mechanical and hydraulic reliabilities. Time-dependent failure of pipelines is evaluated through a fragility analysis that considers the decrease of wall thickness over time due to corrosion. The impact of internal corrosion on hydraulic performance is also accounted for with a time-dependent roughness model. A notional WDS is used to demonstrate the proposed framework. The results of the case study show that pipe corrosion can significantly impact the reliability of a WDS as it ages. The proposed framework links the deterioration of pipeline strength and hydraulic performance with system reliability and can, therefore, form the basis of a reliability-based plan for maintenance and rehabilitation.