Post-Fire Seismic Performance Evaluation of Reinforced Concrete Structures

Fire represents a major hazard likely to occur during the service life of structures, with the potential to severely impair their load-bearing systems. Evidence from past disasters particularly the Northridge and Kobe earthquakes-has revealed that post-fire conditions can dramatically heighten the seismic vulnerability of reinforced concrete buildings. Elevated temperatures reduce compressive strength, lower stiffness, promote thermal cracking, and weaken the bond between concrete and reinforcing steel, all of which diminish load-carrying capacity and alter failure mechanisms. Given these risks, evaluating the seismic behavior of fire-damaged structures is a critical task in structural engineering. In the present study, a typical ten-story reinforced concrete frame was exposed to temperatures between ۲۰°C and ۸۰۰°C. Its seismic performance was then assessed using nonlinear time-history simulations under the Kobe and Northridge ground motions. The findings show that temperature rise can reduce base shear capacity by approximately ۴۳% and increase seismic displacements by ۱۰-۱۲% within the critical range of ۴۰۰-۵۰۰°C. In the same range, response accelerations dropped by as much as ۶۰%, indicating a longer natural period and reduced effective stiffness. Beyond ۶۰۰°C, the structure exhibited unstable and brittle dynamic behavior, suggesting a higher likelihood of sudden and progressive failure in primary members. These results indicate that a temperature of around ۴۰۰°C may serve as a critical threshold for post-fire seismic performance, above which targeted seismic strengthening becomes essential to ensure safe continued operation. Overall, this research underscores the importance of considering the combined fire-earthquake hazard and provides a sound technical basis for improving assessment and retrofitting guidelines for fire-damaged reinforced concrete structures in seismically active regions.

کلیدواژه ها:

Post-Fire Performance ، Reinforced Concrete Structure ، Nonlinear Static Analysis ، Dynamic Analysis ، Seismic Performance