Study On The Shear Performance And Detachable Exchange Performance Of T-shaped Steel Bolt Connector

The construction process has a significant impact on the ecological environment,resulting in increasingly prominent issues such as pollution.In the face of the above problems,the traditional construction method with low resource utilization and high pollution needs to be changed urgently.Prefabricated steel-concrete composite beam has become a research hotspot in the field of civil engineering in recent years because of its good mechanical performance.In practical engineering,bolted connectors are usually used to realize the assembly of steel-concrete composite beams,but the current detachable connection structure often causes damage to concrete and can not realize the reuse of concrete slabs.It is difficult to disassemble and replace steel-concrete composite beams.Moreover,the mechanical properties of bolted connectors are easily affected by the pouring quality of concrete or grouting material.In order to solve the above problems,a detachable and replaceable T-shaped steel block bolted connector is proposed in this paper,and its shear performance and removable performance are studied.The main research work is as follows:The proposed detachable T-shaped steel block bolted connector(T-shaped steel block bolted connector,hereinafter referred to as TSBC)is introduced.Nine TSBC connectors were designed and manufactured,and push-out tests were carried out to study the effects of bolt strength,concrete slab form and bolt diameter on the shear performance of TSBC connectors.The test results show that the failure mode of the other specimens is bolt shearing except for the concrete slab with bolt diameter 27 mm,the shear bearing capacity,shear stiffness and ductility of TSBC connectors increase with the increase of bolt strength and bolt diameter,and the cast-in-place concrete slab can improve the shear capacity and shear stiffness and reduce the ductility of the specimen.Disassemble the bolt-cut specimen and replace the new TSBC connector,and then use the same loading system to carry out the push-out test,mainly study the detachability and shear performance of TSBC after loading.According to the test results and the process of disassembly and replacement,the detachable index(disassembly time,bolt diameter and crack width,number)and disassembly standard are put forward.The test results show that the failure mode of the TSBC connector is still bolt shear,and when the bolt diameter is 22 mm,the concrete slab has more cracks and the crack width is larger than that under the first load.therefore,the removable performance of the connector is affected,and it is not recommended to reuse it more than twice.When the diameter of the bolt is less than 22 mm,there is no obvious crack on the concrete slab,and the bearing capacity and shear stiffness of the connector are improved,the whole process of disassembly and replacement is fast and convenient,and the TSBC connector has good removable performance.Using ABAQUS finite element software for finite element modeling and analysis of the pushout test,the main research focuses on the impact of parameters such as Tshaped steel block strength,concrete strength,transverse reinforcement ratio of concrete slabs,bolt diameter,and bolt strength on the shear performance of TSBC connectors,while ensuring their interchangeability.The results show that the bolt diameter has a significant effect on the shear performance of the connector,and the bolt strength and Tshaped steel block strength will affect the shear performance of the connector,in which the bolt strength mainly affects the shear bearing capacity of the specimen.The Tshaped steel block strength mainly affects the shear stiffness of the specimen,but the improvement of bearing capacity is not obvious when the bolt strength exceeds 10.9grade.In addition,the transverse reinforcement ratio and concrete strength of concrete slabs have little influence on the shear performance of connectors,which can be ignored.Based on the experimental results and finite element analysis results,referring to domestic and foreign standards and existing research results,a formula for the shear bearing capacity of TSBC connectors is proposed while ensuring their interchangeability;Use the least squares method to fit some representative data points in the load displacement curve obtained from the first loading of the experiment,and establish a load slip relationship model for TSBC connectors;Based on the definition of shear stiffness,a shear stiffness degradation model for TSBC connectors is established using the proposed shear bearing capacity formula and load slip relationship model.