Flexural strengthening of fire-damaged GFRP-reinforced concrete beams using CFRP sheet: Experimental and analytical study

Abstract

Since the strengthening of fiber-reinforced polymer (FRP) bar-reinforced structures after a fire incident has rarely been considered in research works, in this work, the flexural response of plain and fiber-reinforced concrete beam specimens with embedded glass FRP (GFRP) bars strengthened with carbon FRP (CFRP) sheets was examined after a fire. Variables understudy in 10 GFRP bar-reinforced concrete beams included the exposure temperature (20, 400, and 600 °C), percentage of steel fiber in volume (0 and 1%), ratio of rebars (0.00314 and 0.00872), and CFRP sheet layers (0, 1, and 2), together with the presence or absence of the U-shaped anchorage. After conducting the four-point quasi-static bending experiment on the non-heated and heated beams, several parameters including the ductility, cracking pattern, and failure mode of the beams, together with their load–deflection diagrams, were assessed. The results showed that the flexural strengthening using CFRP sheets improved the flexural capacity of the specimens and this performance improvement became more notable with an increase in the exposure temperature. In the end, the sectional analysis method was utilized to propose an analytical model capable of estimating the load–deflection response of beams strengthened with CFRP sheets; this model properly estimated the test results.