Flexural behaviour of RC beams with a UHPFRC top layer and hybrid reinforcement of steel and glass fiber reinforced polymer bars

This study aims to conduct an experimental investigation of the flexural behavior of reinforced concrete (RC) beams reinforced with hybrid steel and glass fiber-reinforced polymer (GFRP) bars. The influence of employing ultra-high-performance fiber-reinforced concrete (UHPFRC) as top layers on the beams are also investigated. Eight under-reinforced concrete beams measuring 120 × 185 × 1500 mm underwent four-point flexure testing. These beams were divided into two groups: Group "1" beams had their tension strength improved by using GFRP bars, whereas Group "2" investigated the improvement of tension strength by using GFRP bars and compression strength by using a UHPFRC mix for the top layer of beams. The study's objectives include analyzing the crack pattern, failure mode, first-crack and ultimate loads, load-deflection behavior, bar strain curves, first-crack and ultimate moments, and energy ductility. The results show that using a hybrid system consisting of steel and GFRP bars for longitudinal reinforcement, together with UHPFRC as top layers, resulted in a significant improvement in RC beams' flexure capacity. • The flexural behavior of RC beams with steel, GFRP bars, and UHPFRC layers was investigated. • The crack patterns, failure modes, loads, and energy ductility were analyzed for eight RC beams. • Using UHPFRC as the top layer increases the ultimate load of beams by 23 %. • A hybrid approach using steel and GFRP bars increased the beams' flexure capacity by up to 39 %.