| The steel-concrete composite beam is a structure that combines the steel girder and the concrete bridge deck into a whole and bears the force together.It gives full play to the excellent performance of steel tension and concrete compression,and realizes the balance of bridge span and economy.Shear connector is the key component to prevent the relative sliding of steel girder and concrete slab and ensure the cooperative stress.With the improvement of bridge span capacity,stud connectors and perfobond rib connectors are difficult to meet the shear requirements of some long-span steel-concrete composite girder bridges.For the steel-concrete composite beam bridge with large shear demand,a discontinuous PBL shear connector with transverse welding nails is improved.The mechanical properties and design methods are studied by using the push-out specimen and simulation model.The main research contents and results are as follows:(1)The push-out tests of composite shear connectors under different structural parameters were carried out.Ten compressive composite shear connectors and one non-compressive composite shear connector are designed and manufactured.The influence of end pressure bearing mode on the shear strength and shear stiffness of composite shear connectors is clarified.The failure mode and load slip curve of composite shear key concrete slab and rigid member under the influence of concrete strength,rib thickness,rib hole diameter and stud diameter are explored.The results show that the shear strength of the composite shear connector is better than that of the composite shear key,and the shear strength of compressive composite shear connector is better than that of non-compressive composite shear connector.(2)The finite element simulation and parameter analysis of the push-out failure of shear connector is carried out.The numerical models of stud,PBL and compressive composite shear connectors are established,and the reliability of the simulation model is verified according to the test results.Based on the experimental variables,108 finite element models of compressive composite shear connectors are established and analyzed,and the relationship between the shear strength of compressive composite shear connectors and various parameter variables is deduced.The results show that the shear strength of compressive composite shear connectors is approximately linear with the square root of concrete strength and the thickness of rib plate,and is approximately proportional to the square of rib hole diameter and stud diameter.(3)The shear strength calculation model of compressive composite shear connector based on superposition method is proposed.The shear strength prediction models of stud shear connector and PBL shear connector are summarized,and the correlation between shear load components of composite shear connector and push-out load of stud and PBL shear connectors is compared.The shear strength prediction model of compressive composite shear connectors is proposed by using the superposition method,and the calculation accuracy of the proposed shear strength model is evaluated by using the test and numerical analysis results.The results show that the shear strength calculation formula of compressive composite shear connectors proposed in this study has clear physical significance,and the calculated values are in good agreement with the simulation and test results,which can provide a reference for the design and engineering application of composite shear connector. |
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