Seismic Fragility Analysis of Arch Dam Based on IDA and ETA Methods

In the assessment of the seismic performance of ultrahigh-arch dams, challenges such as complex structural models, extensive degrees of freedom, and extended computation times are commonly encountered. Consequently, there is a pressing need to develop a more streamlined and effective approach for investigating the seismic behavior of ultrahigh-arch dams. The endurance time method, a novel approach in seismic analysis, is increasingly favored for the dynamic analysis of large structures. In this study, the dynamic damage characteristics of an ultrahigh-arch dam are analyzed based on the endurance time method, and the seismic fragility analysis is evaluated. Utilizing a case study of an ultrahigh-arch dam in southwest China, a comprehensive three-dimensional nonlinear model encompassing dam, bedrock, and water interactions is developed. This model incorporates considerations of dam and bedrock damage, cracking, dynamic behavior of contraction joints, and the interaction between the dam and reservoir water. The nonlinear least-squares function is used to generate three endurance time acceleration functions (ETAFs) based on the response spectra of the hydraulic structure seismic design standard. The dynamic analysis of the above model is carried out by using the endurance time method and the incremental dynamic analysis (IDA) method. The results indicate that the endurance time method can well reflect the fragility of ultrahigh-arch dams under different intensities of ground motions, with significant computational efficiency.