Behavior and design of reinforced concrete frames retrofitted with steel bracing against progressive collapse

• Published in: The structural design of tall and special buildings Vol. 29; no. 12
• Main Authors: Yu, Jun, Gan, Yi‐Ping, Ji, Jian
• Format: Journal Article
• Language: English
• Published: Oxford Wiley Subscription Services, Inc 25.08.2020
• Subjects: Catastrophic collapse; Collapse; Computer simulation; Design; Finite element method; Fragility; fragility analysis; incremental dynamic analysis; Lateral stability; Mathematical models; Monte Carlo simulation; progressive collapse; Reinforced concrete; reinforced concrete frame; Reinforcement (structures); Reinforcing steels; Retrofitting; retrofitting design; Seismic engineering; Seismic stability; Steel; steel braces; Steel frames; Steel structures
• DOI: 10.1002/tal.1771
• ISSN: 1541-7794

Summary Steel bracing is able to improve progressive collapse resistance of reinforced concrete (RC) frames, but the bracing design is typically based on seismic retrofitting or lateral stability. There is no approach for design of steel bracing against progressive collapse. To this end, a retrofitting approach with steel braces is proposed based on analysis of macro finite element (FE) models with fiber beam elements. The FE models were initially validated through the experimental results of a braced frame and then used to investigate the effects of pertinent parameters on the progressive collapse resistance of planar frames. The results suggest the braces should be placed at the top story. Thereafter, macro FE models are built to investigate the dynamic responses of the three‐dimensional prototype RC frames under different column removal scenarios (CRS) and show the necessity of retrofitting. Accordingly, the design approach of steel bracing is proposed with incremental dynamic analysis (IDA) and assuming independent contribution of braces and frames to resistance. Finally, the fragility analysis of the frames under a corner‐penultimate‐exterior CRS is conducted through IDA and Monte Carlo simulation, and the results confirm the validity of the proposed design approach for retrofitting RC frames.