Mechanical Performance Study On High-strength Bolt Connectors In Prefabricated Steel-concrete Composite Beams

Mechanical shear connector is a key element to ensure the full use of the two materials in steel-concrete composite beams.In recent years,the country is vigorously developing the prefabricated building.High-strength bolt has the advantages of tight connection,good mechanical performance,fatigue resistance and so on.In order to improve the assembly combination efficiency,as a kind of assembly and disassembly shear connector,it can replace the traditional stud applied to the steel-concrete composite beams.But at present,stud shear connector is one of the most widely used ones in composite beams at home and abroad.There are few researches on the application of high-strength bolts as a shear connector in composite beams,while the majority of researches today mainly focusing on the mechanical performance of high-strength bolt connectors under monotonic static load,rather than its seismic performance.Therefore,this thesis conducts experimental research and finite element(FE)analysis on the mechanical performance of high-strength bolt connector in prefabricated composite beams under monotonous and repeated loads.The main research contents and results are listed as follows:(1)10 high-strength bolt shear connector specimens were conducted under positive push-out load for researches about the influence of high-strength bolt diameter(12 mm and 16 mm)and pretension force(0.2P,0.5P and 0.8P,P is the pre-tightening force specified in GB 50017—2017 code for design of steel structures)on the failure mode,shear bearing capacity,load-slip relationship curve and other shear performance of the connector.The results show that the shear capacity of high-strength bolt connectors increases with the increase of bolt diameter and the bolt pretension has little effect on the shear capacity.(2)11 high-strength bolt shear connector specimens were conducted under repeated load for researches about the influence of high-strength bolt diameter(12 mm and 16 mm),pretension force(0.2P,0.5P and 0.8P)and different loading regimes for high-strength bolt connector on failure mode,shear bearing capacity and ductility.The results show that the shear capacity of high-strength bolt connectors increases with the increase of bolt diameter under repeated load.Different loading regimes and loading systems have certain effects on the shear bearing capacity and ductility of high-strength bolt joints.(3)ABAQUS was used to develop the three-dimensional finite element model and study the shear bearing capacity of prefabricated steel-concrete composite beams with high-strength bolt shear connector.The numerical model involved the nonlinearities of steel,concrete,high-strength bolt,in-fill concrete and other materials as well as contact among components.Validated against the experimental results,the structural performance of the high-strength bolt diameter,tensile strength,length-diameter ratio and pretension as well as the strength of concrete was discussed.Parameter analysis shows that the ultimate shear capacity of high-strength bolt connectors was improved with the increase of bolt diameter,tensile strength of bolt and concrete strength.