Shear Performance Of Bolted Shear Connectors In Steel-concrete Composite Structures

In the steel-concrete composite structure,bolted shear connectors can realize the rapid assembly,disassembly and replacement of the structure,and can replace the traditional studs to improve the assembly efficiency,which has good economic and social benefits.With the development of composite structures,bolted shear connectors are gradually used in composite structures,and the stress and use state of bolted shear connectors in composite structures are more complex.Therefore,the shear performance of bolted shear connectors under prefabrication and casting is studied by push-out test.In order to study the basic mechanical properties of bolted shear connector under different stress states,the push-out test model of bolted shear connector is established by finite element software ABAQUS,and the initial elastic behavior and its influencing factors are studied.Furthermore,the shear capacity of bolted shear connectors and its influencing factors are studied to provide reference for subsequent experimental research.The research of this paper includes the following sections:(1)The modeling analysis is carried out on the push-out specimens of eight groups of bolted shear connectors.Considering the two working conditions of shear model and shear-tensile model,the parameters of three kinds of bolted shear connectors(double embedded nut bolts,single embedded nut bolts and no embedded nut bolts)are analyzed.The influence of different parameters on the initial elastic stiffness is analyzed,and the coupling relationship between different directional stiffness(tensile stiffness and shear stiffness)is analyzed.The structural mechanism and influencing factors of three kinds of bolted shear connectors in the initial elastic stage are discussed.The results show that the bolt diameter,concrete strength,elastic modulus of steel beam and bolt pre-tightening force have an important influence on the initial elastic behavior of bolt.Finally,the fitting formula of elastic stiffness in different directions of bolted shear connector is established by linear regression and the obtained stiffness formulas are applied to the composite beams to analyze the structural characteristics of composite beams in the elastic stage.(2)Four groups of push-out specimen models of bolted joints are established to analyze the influence of bolt diameter,bolt length,concrete strength and bolt pretightening force on shear bearing capacity,and further analyze the influence of different degrees of drawing force on shear bearing capacity in the shear model.The results show that the bolt diameter is an important factor affecting the shear capacity of bolts.With the increase of bolt diameter,the shear capacity of bolts is significantly improved.Concrete strength has an important influence on shear capacity,but when the concrete reaches a certain degree,the influence on shear capacity is no longer significant.Bolt pre-tightening force is useless when the bolt enters the plastic stage,but the influence of shear bearing capacity is not obvious.After applying the drawing force in the shear model,the shear bearing capacity has a reduction effect.With the increase of the drawing force,the weakening degree is more obvious.Through the comparison between the fitting formula of shear capacity and the bearing capacity simulated in this paper,the results are in good agreement,indicating that the model has certain reliability.(3)The shear performance of bolted shear connectors in cast-in-place and prefabricated forms is studied by push-out test.Two specimens are designed,one is cast-in-place specimen,and the other is prefabricated specimen.The test results show that although the prefabricated specimens enter the plastic stage earlier,the shear bearing capacity of the prefabricated specimen is consistent with the cast-in-place specimen.Further comparison between the experiment and the finite element model shows that the finite element results are in good agreement with the experimental results,which further verifies the correctness of the numerical analysis model in this paper.