Experimental study of a novel continuous FRP-UHPC hybrid beam

Abstract In this study, the ultra-high-performance concrete (UHPC) with high tensile strength and cracking resistance was used in lieu of concrete, aiming at improving the mechanical performance and durability of continuous beams under hogging moment. A novel high-performance and high-durability continuous FRP-UHPC hybrid beam was thus investigated, consisting of an I-shaped pultruded GFRP profile with web strengthened by externally bonded carbon FRP (CFRP) sheets, and an overlying UHPC slab. One FRP-concrete and six FRP-UHPC two-span continuous hybrid beams were tested to evaluate effects of slab material, thickness of UHPC slab, reinforcement area and loading pattern. Test results revealed that most continuous FRP-UHPC hybrid beams failed in compression at the bottom flange of FRP profile beam at the middle support. The employment of UHPC slab substantially improved the cracking load by 259.2%, maximum load by 206.4%, stiffness by 38.9% and ductility by 35.0% compared with FRP-concrete hybrid beam. The cracking performance and load-carrying capacity were increased with the increase of the thickness of UHPC slab and reinforcement area. The cross-section strain distribution indicated that the plain section assumption was valid in both positive and hogging moment zones. The small interfacial slippage demonstrated a full composite action between FRP and UHPC.