| As a kind of post-installed shear connector,the bolt shear connector has been widely studied in recent years because it plays an important role in improving the construction effic iency of composite beams and is easy to install and disassemble.However,the research results for the effect of multi-row layout on its shear performance are still insufficient.In view of the existing problems,this paper studies the shear performance of bolt connectors with multi-row layout by push-out experiments,numerical analys is and theoretical analysis.The main research works are as follows:(1)The effects of bolt number,bolt row distance and reinforcement measure on the shear performance of bolt connectors were studied through 10 push-out experiments.The results show that bolt fracture failure occurred in all specimens,and concrete peeled off in the area around the preformed holes on the inner surface of the s lab.The average shear capacity of a single bolt with two rows and three rows of bolts is smaller than that with s ingle row.Therefore,it is necessary to consider the negative effect of bolt with multi-row layout on the ultimate shear resistance of bolt shear connectors,but the vertical spacing of the bolts has little effect on the average ultimate shear capacity of the bolts;reinforcement measure can help to restrain the generation and expans ion of concrete cracks near the preformed holes,but it may not be conducive to the load redistribution among bolts in the loading process,thus adversely affecting the shear performance of the bolt shear connector.The slip corresponding to the fracture of the first bolt in all specimens is between 13.4 mm and 20.4 mm,which show that bolt shear connectors have good ductility.(2)Based on the finite element analysis software ABAQUS,14 finite element models were established to study the influence of multiple parameters on the shear performance of bolt shear connectors under mult i-row layout.The results of finite element analysis show that increasing the bolt preload and the friction coefficient of the interface between the steel beam and the concrete slab can significantly increase the shear stiffness of the bolt connector during the frictional stage,with a maximum increase of 39.5% and 162.6%,and they can also increase the shear bearing capacity of bolted connectors,but the increase is limited;increas ing the concrete strength and the reinforcement ratio of the transverse reinforcement will also increase the shear capacity of bolt connectors,but the increase is not significant;increasing the diameter of bolts can effectively improve the shear capacity of bolt connectors,but the shear capacity does not increase linearly with the shear area of bolts.(3)With reference to the existing calculation methods for the shear capacity of connectors,a shear capacity calculation method and a load-slip theoretical model of the bolt connector considering the effect of multiple rows of bolts were established.Compared with the existing calculation methods proposed in relevant specifications and literatures,the maximum error between the calculation results based on the calculation formula presented in this paper and the shear capacity obtained by the experimental and finite element analysis is 8%,which is the highest consistency and the least discreteness.The research results of this paper can be used as reference for the design of the shear performance of bolt connectors and the subsequent research on the push-out tests of bolt connectors. |
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