The Effect of High Temperatures on the Seismic Ductility Behavior of Exterior Beam-Column Joints in Reinforced Concrete Frames

Document Type : Article

Authors

Faculty of Civil Engineering, Imam Khomeini International University, Qazvin, Iran.

10.24200/j30.2024.64768.3342

Abstract

Beam-column joints (BCJs) are key regions for internal forces transmission in moment frame structures. Large amounts of shear forces and flexural moments should be transmitted among members by the performance of BCJs during seismic excitations. Given that many fired reinforced concrete (RC) structures are again utilized after exposure to fire incidents, the necessity of attention to the vulnerability of RC BCJS under high temperatures should be considered a crucial matter for after-fire exploitations. This study aims to address a research gap in this context by investigating the post-fire ductility behavior of exterior RC BCJs in moment frame structures. In this way, the experimental investigations were considered to identify the vulnerability procedure of these joints under high temperatures of three heating regimes with different target temperatures of 400°c, 600°c, and 800°C. Four scaled RC BCJ specimens were designed according to the seismic provisions of ACI318-19 and fabricated in the same way in the laboratory. The specimens included one control BCJ specimen for investigating the ambient temperature and three BCJ specimens for investigating after exposure to the heating regimes in an electric furnace chamber. A displacement-control cyclic lateral loading was applied for the seismic performance assessment of BCJ specimens in the laboratory. Based on observations, applied heating regimes caused noticeable changes in the crack pattern and failure mode of the control BCJ under lateral loading in such a way that the ductile beam-end hinging failure mode in the control BCJ changed to the non-ductile shear ruptures at the joint core in heated BCJs. The potential effect of high temperatures on the load-bearing capacities and relative energy dissipations was found by considerable reductions in the range of 16.1%-62.3% and 28.8%-65.3% respectively. Also, the ductility factor was reduced for heated BCJs by 14.5%-41.7% relative to the control specimen.  Even though different trends in variations were observed for quantitative values of ductility factors compared to the load bearing and relative energy dissipation, generally, noticeable degradation in seismic ductility behavior was manifested under the effect of applied heating regimes.

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References

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Sharif Journal of Civil Engineering
Volume 41, Issue 3 - Serial Number 3
December 2026
Pages 77-87

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