Experimental And Calculation Method Research On Shear Performance Of GFRP Profile-UHPC Hybrid Beam

Fiber reinforced polymer(FRP)has excellent performance,when combined with other building materials,it can effectively improve the durability of the structure.In recent years,FRP profile-concrete hybrid structures,especially FRP profile-concrete hybrid beams,have attracted widespread attention in research and engineering applications.FRP-concrete hybrid beams fully utilize the advantages of materials by combining lightweight and high-strength FRP with concrete with excellent compressive properties.Compared with the FRP profile-concrete hybrid beam,the FRP profile-UHPC hybrid beam structure has lighter weight,higher bearing capacity and durability at the same cross-sectional size,which can meet the needs of heavy traffic and extend the service life of the bridge structure.However,the research on the force performance and calculation method of FRP profile-UHPC hybrid structure is still immature in the world,and the lack of corresponding design regulations hinders the popularization and application of this type of structure.In this paper,two groups(a total of 12)GFRP profile-concrete hybrid beams are designed.Based on thet experiments,numerical simulation and theoretical analysis,the shear performance of hybrid beams is studied,and the failure mode,flexural stiffness,and anti-slip ability of hybrid beams are analyzed,and the calculation method of GFRP profile-UHPC hybrid beam is studied.The main research contents and conclusion of this paper are as follows:(1)Based on the four-point bending test of 1 GFRP profile-concrete hybrid beam and 7 GFRP profile-UHPC hybrid beams,the shear performance of hybrid beams of different concrete types,interface connection methods,concrete thickness and shear-span ratio are studied.Compared with the GFRP profile-concrete hybrid beam,the GFRP profile-UHPC hybrid beam has obvious advantages in terms of anti-slip ability,flexural stiffness and ultimate bearing capacity;a new type of interface connection method(bolt+SIP-SK)is adopted,and the test results show that the bolt+SIP-SK interface has the best anti-slip ability;while keeping the interface connection mode unchanged,as the shear-span ratio increases,the flexural stiffness of the test beam decreases.When the shear-span ratio is 4.4,the ultimate bearing capacity of the hybrid beam is the highest.When the UHPC thickness increases from75 mm to 90 mm,the ultimate bearing capacity of the hybrid beam increases by10.50%.When the thickness of UHPC slab increases from 90 mm to 105 mm,the flexural stiffness of hybrid beams has significantly improved,but the ultimate bearing capacity does not show much difference.Based on the experiment,the ABAQUS software is used to carry out the numerical simulation of the GFRP profile-UHPC hybrid beam with bolted connection.The numerical simulation results are in good agreement with the experimental results.(2)Based on the four-point bending test of 4 GFRP profile-concrete hybrid beams with local UHPC and bolted connection,the shear performance of the GFRP profile-concrete hybrid beams with local UHPC and bolted connection showed good results in the test;even after the interface slip,it still has high bearing capacity;the strain distribution along the height direction of the mid span section basically conforms to the plane section assumption;the test beams with different hole forming methods show different failure modes.Compared with GFRP profile-ordinary concrete hybrid beam,the ultimate bearing capacity of hybrid beam with local UHPC is improved;under the same width of UHPC hole,the ultimate bearing capacity of the test beam with continuous UHPC hole is significantly higher than that of the test beam with discontinuous UHPC hole.Under the same hole forming method,different width of UHPC hole has an effect on the ultimate bearing capacity of hybrid beam,but the failure mode of the test beam has not changed.On the basis of the test,ABAQUS software is used to simulate GFRP profile-concrete hybrid beams with local UHPC and bolted connection.The numerical simulation results are in good agreement with the test results(3)The calculation formula of the deflection of GFRP profile-concrete hybrid beam under the influence of sliping is established,and the closed equation of calculating shear stress of GFRP profile-concrete hybrid beam is derived.The distribution of shear stress along the section height and the location of the maximum shear stress are obtained.It is found that the shear stress is mainly borne by the GFRP profile,and there is a mutation at the junction between the flange and the web,showing an obvious uneven distribution in the whole cross section,and the shear contribution of UHPC can not be ignored.According to the test results of this paper,the formulas of ultimate shear capacity given in relevant literature are fitted from the angle of UHPC height and shear span ratio,and the calculated results are closer to the test results...