Experimental behavior of fire-exposed reinforced concrete slabs without and with FRP retrofitting

In this study, experiments were conducted on nine reinforced concrete slabs which were divided into three groups, namely S0, S45, and S75. Group S0 included one slab which was not exposed to fire to use as the control specimen. Each of groups S45 and S75 included four slabs which were subjected to 45 min and 75 min of fire, respectively. After exposure to fire, two fire-exposed slabs of each group were retrofitted using fiber reinforced polymer (FRP). These slabs were monotonically or cyclically loaded to failure. The test results showed that the control and fire-exposed slabs exhibited flexural failure while the FRP-retrofitted fire-exposed slabs failed in the form of FRP debonding. Fire slightly decreased the ductility but it was still much larger than 4, classifying the specimens to be highly ductile. Fire marginally reduced the yield and ultimate strengths while it significantly reduced the stiffness by about 30%. Retrofits with 1/2 and 1 FRP layer for fireexposed slabs increased the yield strength by 30% and 45% and increased the ultimate strength by 46% and 65%, respectively. The effect of cyclic loading caused negligible strength degradation, but it caused considerable stiffness degradation of 20% and 35% for the 1/2 and 1 FRP retrofitted fire-exposed slabs, respectively. Finally, a theoretical model was developed to compute the capacity of FRP retrofitted fire-exposed slabs. The model can be useful for engineers to estimate the capacity of FRP retrofitted fire-exposed slabs in practice.

Automated summary

In this study, experiments were conducted on nine reinforced concrete slabs to investigate the behavior of fire-exposed slabs and the effectiveness of FRP retrofitting. The results showed that fire exposure reduced the ductility and stiffness of the slabs, but had minimal effect on the yield and ultimate strengths. Retrofitting with FRP significantly increased the yield and ultimate strengths of the fire-exposed slabs. The effect of cyclic loading on the strength degradation was negligible, but it caused considerable stiffness degradation. A theoretical model was developed to estimate the capacity of FRP retrofitted fire-exposed slabs.