Research On Mechanical Properties And Bearing Capacity Analysis Of Shear Connectors In Steel-UHPC Composite Structures

With the application of ultra-high performance concrete(UHPC),steel-UHPC composite structure has been rapidly developed in bridge engineering.As a key component of the steelUHPC structure,the mechanical properties of shear connectors have a significant impact.In this paper,the mechanical properties of shear connectors in steel-UHPC composite structures are studied by the method of push-out tests combined with finite element simulation.The main contents include:(1)Based on the analysis of the push-out test results of two common shear connectors,the mechanical performance indexes of two shear connectors in UHPC concrete were obtained,including load-slip curve,strain-load curve,shear stiffness.Based on the load-slip relationship,two and four loading stages were defined respectively for the stud and PBL connector,and the characteristics of each stage were described in detail.A new method for drawing up the shear stiffness of two kinds of shear connectors is proposed.The bearing capacity performance of the two types of shear connectors is compared,and within a certain range,the diameter parameter has a significant influence.The bearing capacity of PBL connectors is much higher than that of stud connectors.(2)Combined with the finite element analysis software ANSYS to simulate the studs,PBL and their combined form connectors.The stress and strain of the three kinds of shear connectors and the change of the stress state in the whole process are explained in detail.The three types of shear connectors have been greatly improved in UHPC.Among them,the strength level of stud connectors is lower than that of UHPC,which determines the lower limit of the bearing capacity of the composite structure.The PBL connector and UHPC cooperate well,exerting their excellent performance.The combined connector has the performance of surpassing the average of the former two and has a good development prospect.(3)The calculation methods of ultimate bearing capacity of stud and PBL connectors are summarized,the main influencing factors of ultimate bearing capacity of shear connectors in steel-UHPC structures are determined based on tests and finite element analysis,and the calculation formulas of ultimate bearing capacity of two kinds of shear connectors suitable for steel UHPC composite structures are proposed.