Performance-based failure risk evaluation of transmission tower-line systems subjected to sequential earthquakes

Transmission tower-line systems (TTLSs) are critical components of electricity transmission networks and are typically designed to withstand initial damaging earthquake events without considering the effects of subsequent aftershocks. Subsequent aftershocks could cause additional damage to the mainshock-damaged structures, resulting in further degradation of their strength and stiffness. To quantify the adverse effects of aftershocks, this paper conducts a probabilistic investigation of the seismic fragility and risk of a TTLS subjected to sequential earthquakes. A selection of actual mainshock-aftershock (MSAS) sequences is initially drawn from an international strong motion database, and various techniques for artificially generating sequential earthquakes-including repetition, stochastic, and attenuation construction methods-are introduced. Subsequently, a comprehensive series of nonlinear dynamic analyses on the numerical model of the TTLS is conducted using an ensemble of scaled ground motions to capture the structural damage evolution from elastic behavior to failure. The seismic safety of the TTLS is evaluated through seismic demand models, fragility curves, and seismic risk probabilities. The results emphasize that subsequent earthquakes lead to a deterioration in the seismic performance of the TTLS and the decrease is more than 10 %. Additionally, the attenuation construction method emerges as a viable approximation for real MSAS sequences in the seismic fragility and risk analysis of the TTLS. This research contributes to an understanding of the probabilistic assessment of TTLSs under MSAS scenarios. • Several earthquake-sequence construction methods are compared by the TTLS‘s failure-risk level. • The adverse effect of aftershocks on the mainshock-damaged TTLS is quantified. • The mainshock-damaged TTLS is more prone to additional damage accumulation under subsequent aftershocks. • The attenuation construction method is validated as an approximation for alternative MSAS sequences.