Experimental study on the post-fire seismic behavior of exterior beam-column joints in reinforced concrete frames

This study outlines the post-fire seismic behavior of reinforced concrete beam-column joints. Due to the lack of sufficient research data regarding the seismic vulnerability of exterior reinforced concrete beam-column joints after fire exposure, experimental investigations were carried out to assess variations in the seismic performance of these joints after experiencing high temperatures. In this way, five scaled beam-column joints were considered for examinations and were designed according to the seismic provisions of ordinary moment frames. One benchmark specimen was subjected to reverse cyclic loading at ambient temperature without prior fire exposure. Four others were exposed to the heating regimes with various target temperatures and then examined by reverse cyclic loading after cooling to the ambient temperature. Damage patterns were exhibited with substantial alterations from flexural beam-end hinging for the benchmark specimen to the shear ruptures for the fired specimens exposed to the high temperatures of 400°C, 600°C, and 800°C. The quantitative results indicated minor changes in the load-bearing capacity, ductility factor, and energy dissipation by the effect of the 200°C heating regime. On the other hand, other three heating regimes led to noticeable reductions of 16–62% in the load-bearing capacity, 25–65% in the cumulative energy dissipation, and 14–42% in the ductility factor by propagating diagonal cracks and developing shear ruptures inside the joint core. Trends in variations of investigated parameters were also discussed, and novel findings were presented in this regard. The results and observations in this study can be employed as the applicable data for retrofitting decisions of fired exterior beam-column joints in reinforced concrete ordinary moment frame buildings. • High temperatures caused significant failure mode alterations in the reinforced concrete beam-column joints (RC BCJs). • Shear ruptures were exhibited with different mechanisms in fired BCJs. • Significant reductions in the load-bearing capacity were induced through an approximately linear trend by increasing target temperatures. • Ductility factor exhibited different trend of variations by increasing target temperatures.