Theory And Experimental Research On Steel-concrete Composite Beams With Different Degrees Of Shear Connection

Steel-concrete composite beam is composite structure formed by steel girder and concrete slab.The two parts are connected by the shear connectors,making full use of the advantages of these two kinds of materials.Because of its high bearing capacity,high stiffness and good seismic performance,steel-concrete composite beam has been widely used in all kinds of engineering structures.Shear connector is the key component to make the steel girder and concrete slab work together,providing the shear connect function which is the premise of the bearing capacity of steel-concrete composite beam.The specification defines the degree of connection as the ratio between the number of composite beam's studs and the completely-connect composite beam's,this paper studies the theory and experiment of steel-concrete composite beams with different connection degrees.The main research work consists of four parts:(1)Study of the stud connector push test and static bending test of the composite beams with different connection degrees.Explore the shear bearing capacity and load-slip relation of the stud connectors.Compare the mechanical properties of composite beams with different connection degrees.The results show that,the static failure modes of composite beams with various shear connection degrees are different.The flexural rigidity,bearing capacity and deformation capacity of composite beams all decrease with the decrease of shear connection degree.The composite beam with low connection degree produced two neutral axes in steel beam and concrete slab,and the material performance could not be fully developed.(2)Study of analytical calculation method of composite beams considering interface slip and shear deformation.By establishing the control differential equation,the analytic solution of deflection,slip and stress of the simple supported composite beams under mid-span load is obtained and verified by test data.The value of shear stiffness of composite beam interface and its influence on the relevant calculation results are discussed.Deflection and carrying capacity calculated by this paper is compared with the existing algorithm.(3)Finite element simulation of composite beams.The general finite element software ABAQUS is used to establish the physical unit model and the bending process of the composite beams with different shear connections is simulated.The correctness of the model and the influence of different modeling methods are discussed.On this basis,the orthogonal test and the Python script programming are used for parameter analysis,the results show that,the distance and diameter of the studs have great influence on the mechanical properties of the composite beam but the length and material strength of the studs have little influence.Finally,the relationship between bearing capacity and the connection degree,slip and the connection degree are both fitted.(4)Study of fatigue bending test of composite beams with different connection degrees.The fatigue tests were carried out and the mechanical performances of composite beams with different connection degrees.Based on the experimental results,the fatigue life prediction method of composite beams with different connection degrees under fatigue loads is established.The results show that the influence of the degree of shear connection for fatigue capacity is more significant than for static capacity.It is necessary to use completely shear connected composite beams in fatigue design.