| Reactive powder concrete(RPC)is a kind of cement-based material with high strength,high toughness and low porosity and it has good crack resistance and durability.Applying RPC to the roof of steel-concrete composite beams can solve the problems of longitudinal cracking of ordinary concrete roof,excessive shrinkage and creep,and the limitation of bridge span by dead weight.However,there is currently a lack of research on steel-RPC composite beam stud connectors.In addition,the deformation of studs and the improper welding of studs will lead to the slippage of the interface between steel and concrete.Therefore,a new type of high-strength bond glue-stud connector is proposed to improve the shear strength and stiffness of the interface.The work done in this paper is as follows:1.Through push-out test,the influence of RPC,high strength bond glue and stud on shear resistance of connectors was studied.The results show that compared to ordinary concrete(C50),RPC can be configured without reinforcement and will not crack.The combination of high-strength bond glue and 13 mm diameter stud can greatly improve the shear capacity and shear stiffness of the connector.When combined with the stud with a diameter of more than 13 mm,the shear stiffness of the interface can be significantly improved.Compared with steel-ordinary concrete composite beams,the shear stiffness of studs in steel-RPC composite beams increases greatly,while the shear capacity increases slightly and the ultimate slip decreases slightly.2.ABAQUS model was used to study the shear behavior of high strength bond glue-stud and stud connectors of steel-RPC composite beams.The calculated results are in good agreement with the push-out test results.High strength bond glue can increase the bearing capacity and stiffness of the connectors,but reduce the ductility of the interface.Increasing the diameter of studs has obvious effect on improving the shear capacity,stiffness and ductility of steel-RPC connections.When the ratio of stud length to diameter is greater than 3,the increase of stud length has little effect on the shear behavior of stud connectors of steel-RPC composite beams.The longitudinal spacing of studs in steel-RPC composite beams should meet the requirements of specifications and should not be less than 5 times the diameter of studs.3.Based on the results of push-out test and finite element calculation,the recommended formulas for the shear capacity and stiffness of studs in steel-RPC composite beams are proposed.and the formula of shear load-slip relationship of studs in three-fold form is fitted.The expression of stud deformation and shear stiffness is derived based on the theory of elastic foundation beam.The shear stiffness of the stud calculated by the proposed formula and the theoretical derivation formula is in good agreement with the push-out test results.4.The model of steel-concrete composite beam is established by ANSYS to study the influence of shear stiffness of connectors.The results show that the deflection and stress of steel-RPC composite beams are smaller than that of steel-ordinary concrete composite beams.When the shear stiffness of the connector is greater than 100 kN/mm,the deflection and stress of the composite beam tend to be stable,and the decrease range is very small with the increase of the stiffness.The shear stiffness of the new high-strength bond glue-stud connector proposed in this paper is far greater than 100kN/mm,which can ensure that the shear stiffness of the connector meets the requirements of service.Also,the new high-strength bond glue-stud connector can reduce the risk of concrete cracking around the stud,which prove its effectiveness. |
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