Myths and realities of endurance time analysis: Discussion/Comments Regarding “Seismic assessment of deep water bridges in reservoir considering hydrodynamic effects using endurance time analysis” by Yutao Pang, Li Cai, Wei He, and Li Wu; Ocean Engineering, 2020, 198:106846

Abstract

This discussion is based on the paper by Pang et al. (2020) (hereafter identified as “the original authors” and “the original paper” or “the reference paper”). The original authors employed the endurance time analysis (ETA) and incremental dynamic analysis (IDA) techniques to investigate the probabilistic response of a deep water bridge in a reservoir. They derived multiple fragility curves using both techniques. Derivation of ETA-based fragility functions in the original paper is not fully consistent with the nature of seismic fragility curves. The underpinning concept of fragility curves is tied with ground motion record-to-record (RTR) variability, while the conventional ETA does not offer such an ability. We discussed several underlying assumptions in the ETA method, as well as different sources of ground motion RTR variability (from IDA technique) which may affect the logarithmic dispersion in a fragility curve (and it is unseen in conventional ETA method).