Shear Behavior Of GFRP Profile-UHPC Hybrid Beams: Experimental Study

The research on the shear resistance and design method of the new GFRP-UHPC composite structure is still immature in the world,and the corresponding design rules are still lacking,which hinders the popularization and application of this type of structures.In particular,the synergistic effect between the GFRP profile and the UHPC interface and the contribution of the UHPC plate to the shear capacity of the composite beam is still unknown.Therefore,the experimental study on the bearing performance of the new GFRP-UHPC composite beam is carried out.The shear capacity distribution of GFRP profiles and UHPC is analyzed,the shear failure mechanism is revealed,and the calculation theory of shear capacity of GFRP profiles-UHPC composite beams is improved.Further research and engineering applications have important academic significance and engineering application value.In this paper,nine groups of GFRP-UHPC composite beams were tested for shear resistance.Considering the influence of UHPC height,composite beam shear span ratio and combined structural section form on the shear capacity of FRP profiled composite beams.In order to prevent premature failure of GFRP profiles due to interlayer shear failure or support point distortion instability,ensure that the mechanical properties of each material are fully utilized,and 6 layers of carbon fiber(CFRP)cloth are attached to the side of the beam to carry out the GFRP profile web.Reinforced,with wooden stiffeners to support the loading point and the support.Subsequently,a four-point bending test was carried out.During the test,the interface slip law,ultimate bearing capacity,mid-span deflection value change,and the control section strain of the composite beam were tested.Based on the shear test results of the GFRP profile-UHPC composite beam,the failure modes of the composite beam were analyzed,and the effectiveness of the GFRP profile-UHPC composite beam structure was verified.The results show that when the UHPC height is increased from 30 mm to 50 mm and 80 mm,the bearing capacity of the composite beam is reduced,and the failure mode is also changed from UHPC shear failure to interface failure.Reducing the shear-to-span ratio of the composite beam can effectively reduce the interfacial stress of the composite beam,so that UHPC and composite beam profiles can better exert their material properties;the shear span ratio is reduced from 3.0 to 2.0,and the bearing capacity is increased by 50%;The FRP profile has a 15% to 25% increase in rigidity compared to the I-shaped profile,and the ultimate bearing capacity is increased by 15% to 30%,which lowers the position of the neutralization axis,thereby reducing the interface stress state and making the UHPC material performance fully exerted.Finally,based on the flat section assumption and section analysis theory,a proposed formula for the shear capacity of FRP profiled composite beams is proposed.Based on the experiment,a design idea and calculation method based on elastic design are proposed.The design method and construction measures of the combined interface are proposed.