Resilience-based seismic safety evaluation of pile-supported overhead transmission lines under depth-varying spatial ground motions

Despite the persistent emphasis on the significance of soil-structure interaction (SSI) in the seismic analysis of overhead transmission lines (OTLs), Previous studies on seismic safety of OTLs have typically utilized base-fixed constraints and uniform ground motion inputs, which may result in unreasonable estimations. In light of this observation, this paper aims to evaluate the SSI effect on the seismic safety of a pile-supported OTL exposed to depth-varying spatial ground motions (DVSGMs) from a resilience perspective. Initially, a refined finite element (FE) model is developed for the OTL, meticulously incorporating the buckling and post-buckling effects of steel members. Subsequently, a suite of three-dimensional DVSGMs is stochastically generated considering layered soil properties and ground motion propagation laws. Through systematic exploration, this study investigates the SSI effect on the dynamic responses, fragility probabilities, and resilience metrics of the OTL under DVSGMs. The findings highlight that compared to scenarios where tower legs are directly fixed to the ground, incorporating SSI can yield adverse responses of the OTL and contribute to an increasing uncertainty in its seismic resilience with higher excitation intensities. This research advocates for the integration of SSI and depth-varying spatial effect into the seismic resilience assessment of OTLs.