Establishment and experimental validation of an updated predictive equation for the development and lap-spliced length of GFRP bars in concrete

Glass fibre-reinforced polymer (GFRP) reinforcement due to its physical and mechanical behavior has a completely different bond behavior compared to the steel bars. In this paper, an equation is proposed to predict the splice length in GFRP-reinforced concrete beams. First, equations for the local bond strength and displacement modulus of GFRP bars are obtained by using the eccentric and concentric pull-out test results given in the literature. Then, an equation is derived for the bond strength of spliced GFRP bars in beams. In the derivation of this equation, the non-uniform distribution of the bond stress along the splice length and the effect of elastic modulus of GFRP bars are taken into account. Compared to other available equations and design guidelines, the proposed equation for bond strength calculation shows good agreement with the experimental results. Using the proposed equation for bond strength, an equation is also proposed for the splice length of GFRP bars.