Study on Seismic Collapse Fragility of Corroded Platform Canopies with Different Fortification Intensities in China

Twelve reinforced concrete (RC) railway platform canopies were designed for zones with different seismic fortification intensities (SFIs) in accordance with the Code for Seismic Design of Buildings (2024 Edition) GB/T 50011-2010. Numerical models were created in OpenSees for each structure under three conditions: no corrosion, 5% corrosion loss of reinforcement, and 15% corrosion loss of reinforcement, using the Modified Ibarra–Medina–Krawinkler (ModIMK) hysteretic model. Through IDA, seismic collapse fragility was assessed in accordance with the requirements of the Standard for Anti-collapse Design of Building Structures T/CECS 392-2021. The results are: (1) Double-column canopies strongly resist deterioration from reinforcement corrosion. Each structure with different SFIs meets the code’s collapse probability limit under all three corrosion levels when subjected to the maximum considered earthquake (MCE) and the extreme considered earthquake (ECE, an earthquake larger than MCE). (2) When subjected to MCE, Single-column canopies with different SFIs also meet the code’s collapse probability limit under the three corrosion levels. (3) When subjected to ECE, the collapse probability of single-column canopies with 5% corrosion increases compared to uncorroded structures at SFIs ranging from 6 to 8; for SFIs 8.5 and 9, the collapse probability decreases. The structure with SFI 8.5 has the highest risk and does not comply with the code. (4) When subjected to ECE, the collapse probability of the single-column canopy with 15% corrosion increases significantly compared to uncorroded structures at all SFIs. Structures with SFIs ranging from 7.5 to 9 fail to meet code requirements. This paper systematically investigates the collapse fragility of platform canopies with different seismic fortification intensities in China, examining three corrosion states: no corrosion, 5% corrosion, and 15% corrosion. It provides important guidance for the rational design of platform canopies and for analyzing the impact of corrosion levels on their collapse behavior.