Seismic loss risk and resilience assessment of air traffic control towers considering equipment functionality

Abstract

Seismic loss risk assessments and evaluations of the seismic resilience of tower systems are critical for predicting operational safety at airports during seismic events. A multidimensional fragility model was developed utilizing the peak floor acceleration and the peak interstory displacement angle as seismic demand parameters, with the former indicating the impact on air traffic control (ATC) equipment. On the basis of this model and seismic hazard analysis, a seismic loss risk assessment method was proposed for the tower system, encompassing both the tower structure and ATC equipment. Furthermore, a seismic resilience assessment framework was established using loss and recovery functions to examine the functional degradation and restoration timelines for airport towers. The investigation revealed that the probability of failure for the tower system under near-field earthquakes was significantly greater than that under far-field earthquakes, for example, 38.0 % versus 93.0 % in the immediate occupancy (IO) limit state. When comparing the fragility results based on single versus dual seismic demand parameters, the multidimensional model yields more conservative predictions. For far-field earthquakes in the normal operation (NO) limit state, the fragility curves have failure probabilities of 66.4 %, 24.6 %, and 85.4 % for a single displacement angle, a single floor acceleration, and multidimensional models, respectively. The indirect economic losses of the tower system are significantly higher than the direct losses. Under near-field earthquake conditions at the DS₃ limit state with a 9-degree seismic fortification, the maximum direct economic loss is 1168800 yuan, while the maximum indirect economic loss reaches 6428600 yuan. The functional losses of the tower system and ATC equipment during rare near-field earthquakes under 8 degrees of seismic fortification are 48 % and 10 %, respectively, with corresponding recovery times of 153.6 and 20.36 days.