Seismic performance assessment of high CFRDs based on fragility analysis

Abstract

Due to a large number of high concrete face rockfill dams (CFRDs) being constructed, the seismic safety is crucially important and seismic performance assessment must be performed for such dams. Fragility analysis is a method of great vitality for seismic performance assessment; it can intuitively forecast the structural effects of different ground motion intensities and provide an effective path for structure safety assessment. However, this method is rarely applied in the field of high earth dam risk analysis. This paper introduces fragility analysis into the field of high CFRD safety assessment and establishes seismic performance assessment methods. PGA, Sa (T1, 5%), PGV and PGD are exploited as the earthquake intensity measure (IMs). Relative settlement ratio of dam crest, cumulative sliding displacement of dam slope stability and a new face-slab destroying index (based on DCR and COD) are regarded as the dam damage measures (DMs). The dividing standards of failure grades of high CFRDs are suggested based on each DM. Fragility function is estimated according to incremental dynamic analysis (IDA) and multiple stripes analysis (MSA) methods respectively from a large number of finite element calculations of a certain CFRD, and seismic fragility curves are determined for each DM. Finally, this study analyzes the failure probabilities of the dam under different earthquake intensities and can provide references and bases for the seismic performance design and safety risk assessment of high CFRDs.