Probabilistic demand models and fragility analysis of railway embankments subjected to multi-pulse ground motions

The pulse-like ground motion has a substantial impact on long-period structures such as railway embankments. However, previous studies have focused more on comparative analyses of ground motions with and without pulses, without distinguishing between multi-pulse and single-pulse ground motions. This study aims to quantitatively assess the differences in seismic damage to railway embankments when subjected to various pulse-like ground motions, utilizing the seismic fragility analysis method. We executed an incremental dynamic analysis of railway embankments to construct a probabilistic seismic demand model. The most effective intensity measures (IMs) were chosen from among 20 IMs using criteria of correlation, practicality, efficiency, and proficiency. The conditional probability function facilitated fragility curves by applying the optimal IMs and the engineering demand parameters, which represented the peak permanent settlement on the surface of the railway embankment. The results demonstrated the superiority of structure-specific IMs (e.g., velocity spectrum intensity and housner intensity) over acceleration-, velocity-, displacement-, and time-related IMs. The findings revealed that multi-pulse ground motions significantly impacted the uncertainty of railway embankment damage more than single-pulse ground motions, and ignoring their effects led to an underestimation of their fragility in all states of damage.