Investigation on flexural behavior of novel GFRP grid web-concrete hybrid beam

•The novel GFRP grid web-concrete hybrid beam with reduced self-weight has sufficient flexural strength, stiffness, and ductility.•The GFRP grids are arranged along the principal stress, and the grid joints are embedded in surrounding concrete without the need for separate shear connectors.•The flexural performance of the proposed hybrid beam is investigated through four-point bending load test and numerical study. A novel GFRP grid web-concrete hybrid beam was proposed to solve the problems of traditional concrete T-beam structures, such as heavyweight and easy cracking of the web. The GFRP grids arranged along the principal stress were partially embedded in concrete to achieve reliable connection and avoid the insufficient interlaminar shear strength between GFRP profiles. The flexural behavior of the novel hybrid beam was investigated through experimental and numerical studies. The experimental results indicated that the force form of the GFRP grid web was consistent with the proposed hypothesis, and the section bending moment was mainly borne by flange plates and longitudinal reinforcements. The flexural failure process of the hybrid beam can be divided into three stages: elastic stage, working stage with cracks, and failure stage. No relative slip or stripping was observed between the GFRP grid web and concrete throughout the loading process, indicating that the GFRP grid web could be reliably connected to flanges and vertical ribs to form composite action. The numerical analysis showed that the GFRP grids only contributed 7.30 % to the bending resistance of hybrid beam due to its weak longitudinal stiffness, compared to concrete and reinforcements. The staggered grid plates born the compressive and tensile stresses, while the part embedded in the lower flange plate in the mid-span area was in full-section tension with the maximum tensile stress of 85.7 MPa. The stress distribution of concrete flange plates basically conformed to the plane assumption, while the concrete stress near the support appeared reverse sign phenomenon, since local bending moment was generated in concrete flanges due to the weak longitudinal stiffness of GFRP grid web. Overall, the proposed novel hybrid beam with reduced self-weight retains good flexural strength, stiffness, and ductility characteristics of concrete beams compared to conventional concrete T beams.