Vector-valued fragility analysis of subway station structures subjected to the Kahramanmaras earthquake

The Kahramanmaras earthquake sequence that occurred in Turkey on Feb. 6, 2023 caused significant casualties and economic losses, which may relate to its distinct characteristics. This paper establishes optimal intensity measures (IMs) and vector-valued fragility curves for subway station structures considering the Kahramanmaras motion record characteristics. The seismic records are analyzed in terms of time-history, response spectrum, and seismic IMs, and a numerical model of a subway station with two-story and three-span is developed considering the concrete damage and nonlinear behavior of soil. The optimal IMs are selected according to criteria of efficiency, practicality, proficiency and goodness of fit. Based on the optimal IMs, vector-valued fragility surfaces are developed, and the differences in damage probability between the vector-valued fragility curves and scalar-valued fragility curves are analyzed. The results indicate that the velocity time-histories of the 12 mainshock records exhibit pulse-like characteristics with large peak velocities and displacements along with high amplitudes of the response spectra at longer periods. The velocity-based IM, Vsi, is found to be most suitable for probabilistic seismic demand analysis under the Kahramanmaras earthquake, and along with PGA is utilized as elements for vector-valued IM. Finally, the scalar-valued fragility curves may underestimate or overestimate the failure probability, while vector-valued fragility curves can offer a more accurate failure probability for specific characteristics IMs. •Fault traces and tectonic framework of the Kahramanmaras earthquake sequence are discussed.•Vsi is the most suitable IM for probabilistic seismic demand analysis of subway station under the Kahramanmaras earthquake.•Vector-valued fragility curves offer more accurate estimate with combination of Vsi and PGA for subway station.