Case Studies in Construction Materials (Jun 2022)
Comparative study on the tensile mechanical behavior of GFRP bars under and after high temperature exposure
Abstract
Glass fiber-reinforced polymer (GFRP) bars are being increasingly used in reinforced concrete structures to replace ordinary steel reinforcements as an effective and economical solution to corrosion problems. The mechanical behavior of GFRP bars under and after high temperature exposure is crucial for their application in structures potentially subjected to fire, and further research and comparisons are needed to increase the accuracy of fire-resistant design and post-fire analytical model of GFRP reinforced concrete members. Thus, this paper aimed to study the residual tensile performances of GFRP bars under and after high temperature exposure. The stress–strain curves, tensile strengths, elastic modulus, and ultimate strains of GFRP bar specimens while being subjected to, and after, different high temperatures were tested and compared. The effects of high temperature on the degradation mechanisms of GFRP bars were investigated using scanning electronic microscopy. The results showed that carbonization of resin and exposure of fibers in GFRP bars occurred gradually as the temperature increased. At the same temperature, the tensile failure modes and stress–strain relationships for specimens under and after high temperature were similar. However, the residual tensile strengths and ultimate strains on GFRP bars after high temperatures were greater than those under high temperatures, which ranged from 150 ℃ to 350 ℃, indicating that the different values of those mechanical properties should be taken into account in the analysis of fire resistance and the post-fire identification of concrete structures reinforced with GFRP bars. Finally, regressive models for the residual tensile strengths and elastic moduli of GFRP bars under and after high temperature exposure, respectively, were developed, based on the results of this experiment and previous studies. The calculated results correlated well with the experimental results.
