Influence of Mainshock Aftershock Sequences on the Seismic Vulnerability of Bridges in India

The primary focus of this study is on the generation of artificial mainshock-aftershock ground motion for the seismic vulnerability assessment of bridges in the Himalayan region of India. For this purpose, first a collection of ground motion records for mainshocks is chosen based on the seismic activity in the region. A record database of real recorded mainshock-aftershock sequences is compiled, and linear model is developed to establish a relationship among the mainshock and aftershock ground motions. This model is then utilized to select aftershocks for the chosen mainshocks records, creating artificial mainshock-aftershock sequences. For the Himalayan region, a highway bridge is chosen for case-study and a comprehensive FE model is generated. A sequence of non-linear time-history analyses are conducted at different scaled levels of ground motion intensity to develop seismic fragility curves. Results demonstrates that the median fragility estimates for the complete damage state exhibit a 26% reduction when considering mainshock-aftershock sequences compared to only mainshock records.