Development of fragility curve of transmission tower

Transmission towers are vital channels for distributing high-voltage electrical power from power plants to substations. This infrastructure is the backbone of a productive modern society. However, a number of these towers may fail due to earthquakes. This failure may disrupt the electrical network, yield a substantial amount of replacement cost, and, more importantly, interrupt recovery efforts and business operations. This paper presents attempts to analyze the seismic risk of the transmission tower by developing its fragility curve. Fragility is defined as the probability of damage exceeding a certain level, given an extensive range of seismic intensity. A finite element computational model was analyzed under a nonlinear static procedure (pushover) to obtain a nonlinear response, specifically a capacity curve. Then the fragility analysis was performed by determining certain damage states in the capacity curve. The inter-segment drift ratio (ISDR) was employed for the damage states. The result is expressed as a fragility curve that provides fundamental and rational insights into the mechanical and probabilistic performance of transmission towers.