Methodology for Risk Analysis of Dam Gates and Associated Operating Equipment Using Fault Tree Analysis

摘要

With limited maintenance dedicated to aging dam spillway gate structures, there is an increased risk of gate inoperability and corresponding dam failure due to malfunction or inadequate design. This report summarizes research on methodologies to assist in quantifying risks related to dam gates and associated operating equipment, and how those risks relate to overall spillway failure risk. The objective of the research was to demonstrate how fault tree analytical methods may be applied to improve the quality of dam gate risk analysis. Two different methods of prescreening analysis are presented and evaluated. The first uses probabilities for more events, defined more precisely than in standard practice, and adds criticality ranking; the second uses more traditional estimation of failure probabilities in conjunction with subsystem importance-ranking factors to estimate overall gate system failure probability. Both methods can be linked qualitatively with the Lafitte risk method through event costs and consequences to determine the overall risk for a dam spillway system. Enhancement of the two demonstrated methods would require a direct application of the methods to an existing dam gate system. Also, additional research would be necessary to better determine the risk consequence factor, alpha, used in the Lafitte equation for calculating overall risk.