A New Probabilistic Framework for Structural System Fragility and Sensitivity Analysis of Concrete Gravity Dams

Concrete gravity dams are widely constructed owing to their advantages of low maintenance cost and relatively low risk of sudden failure. However, the structural failure rate has been reported to be higher than other dam types. Although various studies have been conducted to assess the structural fragility of concrete gravity dams, not enough emphasis was placed on system-level fragility and sensitivity analyses, which provide crucial information for mitigating dam failure. This study proposes a new probabilistic framework for system fragility and sensitivity analysis by employing a finite element model for concrete gravity dams. The proposed framework consists of four steps, namely, structural analysis modeling considering the realistic loading conditions, component fragility analysis employing finite element reliability analysis, system fragility analysis employing system reliability analysis, and system sensitivity analysis using the finite difference method, which require several numerical algorithms and computational techniques. The proposed framework is applied to a numerical example of a typical concrete gravity dam in South Korea, and the analysis is completed successfully. As a result, the example dam is found to be relatively more vulnerable to sliding and concrete overstress than ground overstress. In addition, it is revealed that the dam system is more likely to fail in the overflow part than in the non-overflow part. The most critical factor in preventing these failures is the concrete mass density, followed by the silt mass density and the concrete compressive strength. Based on these analysis results, it is confirmed that the proposed framework provides valuable information for risk-informed structural design and failure mitigation of concrete gravity dams.