The tensile performance of FRP bars embedded in concrete under elevated temperatures

Abstract

In this research, the mechanical properties of glass and carbon fiber reinforced polymer (FRP) bars with epoxy resin matrices embedded in concrete were investigated under an extensive range of elevated temperatures (i.e., 25–800 °C). Embedded FRP bars with various bar diameters were studied in order to determine bar diameter influence on the results. In addition, analysis of variance (ANOVA) was performed on the experimental results to investigate the contribution of exposure temperature and bar diameter to the tensile behavior of embedded in concrete FRP bars at elevated temperatures. The results show that the tensile strength of embedded FRP bars generally decreases with increasing temperature; however, the rate of decrease of the tensile strength varies within different temperature ranges due to different failure modes and states of the FRP material. The influence of the bar diameter was not significant in the tensile behavior of embedded FRP bars at various elevated temperatures. However, the influence of the bar diameter increased within the temperature range of 150–500 °C compared to the temperatures lower than 150 °C and above 500 °C. The results also show that the concrete cover prevented direct heat and oxygen from reaching the bars; as a result, embedded FRP exhibited improved tensile performance at elevated temperatures compared to bare bars that were directly exposed to heat. Two Bayesian regression models were developed for predicting the tensile performance of embedded GFRP and CFRP bars at elevated temperatures. The models have been shown to be in good agreement with the experimental results.