Shear Behavior of Novel GFRP Grid Web-Concrete Composite Beam

Glass-fiber-reinforced polymer (GFRP) is widely applied in composite structures to optimize structural performance. The puzzle of heavy self-weight and easy cracking in the web for conventional reinforced concrete (RC) beam can be solved by replacing the RC web with a GFRP grid web. This paper studied the shear behavior of a GFRP grid web-concrete composite beam through three-point loading tests, considering the effects of GFRP material properties, GFRP grid web height, and web type. The experimental results showed that the GFRP grid web and the flange plates failed in oblique shear almost simultaneously in the ultimate state. The shear force of the composite beam could be effectively transmitted, since there were no joint failures of the GFRP grid and connected interface failures between the GFRP grid and concrete observed throughout the tests. The composite beam with reasonable GFRP material strength and proper web height displayed good shear performance, when compared with the RC beam. The numerical analysis indicated that the GFRP grid web contributes to the shear resistance of the composite beam, and the sectional stresses borne by tensile and compressive grids exceeded 95% of their strength. The finite-element parametric analysis showed that the shear resistance of the composite beam could be significantly improved by increasing the grid cell density, grid sectional ratio, and grid specific strength. However, the grid allows a reasonable range for the increase to match the optimal shear performance of the composite beam. In addition, a shear capacity calculation method of the composite beam was proposed, where the nonuniform stress coefficient k of GFRP grid was introduced.