Study the Flexural Behaviour of Concrete-FRP Hybrid Beams Under Three-Point Bending

Abstract

Fiber reinforced polymer (FRP) beams exhibit the brittle failure under three/four-point bending test. Reinforced concrete-FRP hybrid beams show pseudo-ductile characteristics, if the ideal bond formed by mechanical and/or adhesive connectors. Hence, it is important to study the flexural behavior of different connection of reinforced concrete-FRP hybrid beams. In this study, flexural behavior of concrete-FRP hybrid beams is determined. Beams are modeled in finite element software ABAQUS. Shear connection between the FRP beams and RC slab is made using shear connectors and adhesive bonding. Web and flange elements of I-beams are connected with cohesive layer, because it is the weaker portion in the FRP I-beams and is highly prone to fail under three-point loading. Accuracy of the numerical model is verified by comparing the results with published experimental study. Further, the parametric study is performed on beams having different size and spacing of shear connectors. Along with, failure and service load of hybrid beams is determined for different geometric configuration of I-beams and width of RC slab. The flexural response of hybrid FRP-concrete beams obtained from finite element software shows good agreement with experimental testing. It is observed that shear connectors help in improving the strength of concrete-FRP hybrid beams. With increasing the length of shear connectors there is slight improvement in the strength of beam. As density of shear connectors decreases consequently flexural stiffness of the beam (initial slope of load-deflection curve) decreases. It is also noted that strength and stiffness of the hybrid beam increases with increase in the length of the shear connectors. With decrease in the length of the beam, flexural stiffness of the beam increases. The failure and service load is lower for the beams having higher L/d ratio. From the flexural study of the beams having different B/t ratio, it is observed that some beams same failure and service load, it is due to the pre-mature failure of the web-flange junction of the I-beams. Hence, it is stated that addition of RC slab enhances the flexural stiffness, i.e., service load and also enhance the strength of web-flange junction. Addition of reinforced concrete slab over the FRP I-beams, reduces the chances of local buckling of the flange and web of the I-beam.