Seismic fragility analysis using vector IMs and resilience assessment for ATC towers based on equipment seismic demand

Abstract

Ensuring the safety of air traffic control equipment in an airport tower during an earthquake is crucial for safe operations. This study determined seismic demand through maximum acceleration at equipment locations and developed a seismic fragility analysis method using vector intensity measures (IMs). Seismic resilience curves for the tower system were constructed on the basis of the loss function and the recovery function. For a typical tower structure, failure states were defined according to the equipment's performance limits. The peak ground acceleration (PGA) and peak ground velocity (PGV) were chosen as IMs, yielding seismic fragility curves for scalar IMs and fragility surfaces for vector IMs across different performance limits. The effects of vector IMs and both far-field and near-field earthquakes on equipment failure probability were examined, and the impacts of different recovery function models on the seismic resilience of the tower were investigated. The results indicated that using the PGA and PGV resulted in lower variability and error in the seismic fragility analysis. When comparing scalar IMs (PGA or PGV) to vector IMs (PGA and PGV), the equipment failure probability was notably greater for vector IMs. Moreover, the equipment failure probability was greater for near-field earthquakes than for far-field earthquakes. As the PGA increased, the functional loss and recovery time of the tower system significantly increased. Under near-field earthquakes with PGV = 0.5 m/s, the function loss of the tower system was 14.9 % and 44.1 % for PGAs of 0.4 g and 1.2 g, respectively, with recovery times of 5.04 days and 29.35 days. Compared with the linear recovery model and the trigonometric recovery model, the exponential recovery model has greater seismic resilience for towers, under a far-field earthquake with a PGA of 1.2 g, the resilience values from the linear, trigonometric, and exponential function recovery models are 0.911, 0.911, and 0.967, respectively.