Effect of confining stirrups and bar gap in improving bond behavior of glass fiber reinforced polymer (GFRP) bar lap splices in RC beams

Abstract

Fiber-reinforced polymer (FRP) bars are becoming a popular replacement for steel rebars that are vulnerable to corrosion, especially under harsh corrosive environments. Despite several advantages for using FRP rebars, the bond between FRP bars and surrounding concrete has been a major concern that affects the behavior of FRP-reinforced structural members. The experimental program of this study comprises testing eight full-scale glass FRP (GFRP) reinforced beams under two-point loads. There were two control beams and six beams having rebar lap splices. The beams were reinforced using 2ϕ12 GFRP bars. The first control had continuous GFRP bars, and the 2nd control had GFRP lap splice conforming to the relevant ACI code. The lap splice was 65 times the bar diameter in six beams having lap splice. The contact lap and non-contact laps were used along with the variable spacing of shear stirrups in the lap zone (50, 100 mm, ∞, i.e., no shear stirrups). The lap splice, designed conforming to the ACI code, was found to be very conservative. The reduction in shear stirrups’ spacing in the lap zone and the gap between lapped bars was found to enhance the bond performance of GFRP bars by up to 31 %. The authors’ previous models for predicting development length and bond are found to show good predictions for the experimental results of the present study as well. Analytical models are developed for predicting with sufficient precision the peak load for GFRP reinforced beams with the two types of lap splices (non-contact and contact).