Enhancing lap splice performance in reinforced concrete beams using basalt fiber-reinforced polymer confinement

Abstract

Natural fiber-reinforced polymers (FRP) offer a potential alternative for strengthening applications, specifically in cases where the costly nature of synthetic FRP composites is a worry. This work investigates the effects of basalt fiber-reinforced polymers (BFRP) confinement on flexural behavior, peak loads, and bond strength enhancement by conducting four-point bending tests on simply supported reinforced concrete (RC) beams. Large-scale beams were tested in two groups to differentiate lap splice length. Group 1 beams incorporated a lap splice length of 20d_{\text{b}}, whereas a 30d_{\text{b}} lap splice length was used in Group 2 beams (where d_{\text{b}} is the diameter of lap spliced bars). The findings show that BFRP confinement significantly affects flexural stiffness, improves ultimate strength and ductility. Peak load improvement varies with lap splice length, with Group 1 beams showing up to 80.95% increase and Group 2 beams up to 17.31% increase. Bond strength is significantly improved by BFRP confinement, but the effect diminishes with longer splices and larger concrete covers. Existing models are inadequate, so a strain control-based new equation is proposed to predict bond strength enhancement. These findings contribute to understanding BFRP confinement in RC beams and aid in designing cost-effective solutions for strengthening short lap splices.

Graphical abstract

Keywords

basalt fiber-reinforced polymer / lap splice / passive confinement / beams / bond strength / model

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