Empirical Model for Temperature-Dependent Tensile Strength of Glass Fiber-Reinforced Polymer Bars

This paper presents a comprehensive literature review on the thermal behavior of glass fiber-reinforced polymer (GFRP) bars. A database of more than 500 specimens from 11 different studies was created to observe the factors affecting the tensile strength retention of GFRP bars at elevated temperatures. The thermal behavior of GFRP reinforcing bars is influenced by numerous factors, such as the fiber-reinforced polymer (FRP) bar surface, bar size, test methodology, loading rate, and the free bar length exposed to elevated temperatures. A statistical analysis was carried out, and an analytical model is proposed to evaluate the reduction in the tensile strength as a result of temperature exposure. The proposed model, expressed in three stages in a piecewise manner, was validated against studies in two areas: thermal degradation of GFRP bars under elevated temperatures and fire resistance of a GFRP-reinforced concrete RC) beam. A close agreement was found between the predicted and experimental results. The current model is thus suitable for design procedures to determine the fire ratings of GFRP-RC members. Keywords: analytical model; fire resistance; glass fiber-reinforced polymer (GFRP) bars; thermal degradation.