| The main function of shear connector in composite beams is to effectively connect two different materials,and bears the shear force of the structure at same time.Stud are often used as shear connector in traditional composite beams,but in recent years,with the promotion of prefabricated structure in government,bolt is more suitable for assembled composite beams than stud because of it has good mechanical performance and convenient for rapid disassembly.However,the research on the shear behavior of bolt connector is still insufficient.Based on this problem,this paper proposes a kind of embedded steel sheet bolt connectors,and uses the methods of push-out test,nonlinear finite element calculation and theoretical research to study and analyze the shear behavior of bolt connectors.(1)A new type of assembled structure bolt connectors structure is proposed.The effects of pretension,interfacial treatment mode,depth of bolt and anchor reinforcement were studied through 7 push-out specimens based on this structure.The results show that 7 specimens were totally shear failure,no obvious damage was found in other parts of the specimen after loaded.The pretension and interfacial treatment mode mainly affect the initial slip load and initial stiffness,but have little effect on the ultimate bearing capacity.The bolt depth and anchor reinforcement has no obvious effect on the ultimate bearing capacity.The results shows that the proposed structure has good integrity.During the test,the embedded steel plate bolt connectors showed high overall strength and anti-destructive ability.(2)Based on the model validation,7 finite element model was established by nonlinear finite element software ABAQUS.Study the influence of hole diameter,bolt strength,bolt diameter and concrete strength on the shear performance of bolt connecter.The results show that the ultimate bearing capacity of grade 9.8 and grade 10.8 is 20.79%and 33.97%higher than grade 8.8.The ultimate bearing capacity of bolts with diameter of 18mm and 20mm increased by 23.03%and 47.33%compared with that diameter of 16mm,the increase of ultimate bearing capacity of bolt is linear with tensile strength and cross-section area of bolt.The hole diameter and concrete strength have no obvious influence on the ultimate bearing capacity.(3)In order to further study the overall strength and stiffness attenuation of embedded steel plate bolt connectors,the specimens which have been loaded for the first time are reassembled and the secondary loading test is carried out.The experimental results show that the failure mode of the second loading is basically the same as that of the first loading,the influence of each parameter on the ultimate bearing capacity has no obvious change.In the process of secondary loading,the stiffness of some specimens decreases due to internal damage,but the ultimate bearing capacity does not change significantly compared with the first loading.It is proved that the failure of the specimen during the first loading process is limited,and the specimen still shows well strength in the secondary loading process.(4)Based on the test and finite element analysis,the formula for calculating the ultimate bearing capacity of bolts is discussed.The shearslip relationship of bolt connectors is obtained by numerical fitting method,and the concept of shear stiffness is proposed.The shear stiffness of the specimen during two loading processes is discussed and analyzed.The research results of this paper can provide reference and basis for improving the relevant specifications of bolt connectors. |
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