Finite Element Analysis of Transfer-Bracket Joints of Concrete-Filled Steel Tubular Columns

At present,for the connection of steel box beam,its end is usually directly welded to the surface of supporting steel members.This connection method not only has high technical requirements for welding,but also is easy to produce defects at the weld,resulting in weld cracking.For the problems caused by the installation of traditional steel box beam,a new type of prefabricated connection for steel box beam,a transfer bracket joint,is studied.The steel box beam is installed by bolts instead of welding.The transfer bracket joint is to introduce a transfer bracket between steel box beam and concrete-filled steel tubular column.The basic components of transfer bracket include a short middle coupling beam,and two plates which are welded at both ends of the middle coupling beam,including the front plate connected with steel box beam and the endplate connected with concrete-filled steel tubular column.According to the different connection modes,the transfer-bracket type joint can be divided into two forms:corbel type and extended endplate type.
Firstly,the detailed structure of the joint is given,and the effectiveness of the joint finite element model is verified;detailed parametric analysis is carried out to study the influence of the length of coupling beam,flange thickness and width,and endplate thickness on the joint performance;the failure modes of the two types of joints are compared and analyzed.
The results show that the possible failure modes of transfer-bracket joints include large area yield failure of coupling beam,compression buckling of lower flange,yield failure of steel box girder,tensile failure of front end plate,excessive tensile yield deformation of rear end plate and tensile yield of bolts.The increase of the length of the coupling beam has little effect on the initial stiffness and bearing capacity of the joint,but the length of the coupling beam will affect the stress distribution on the beam.With the increase of the length,the stress level on the beam will decrease.But the long coupling beam can not effectively improve the performance of the joint.The minimum length of the coupling beam should ensure the operation space of the torque wrench,and the maximum length should not affect the mechanical properties of the steel box beam.Increasing the section size of the coupling beam can improve the bearing capacity of the joint.With the increase of the section size,the plastic hinge of the beam will gradually transfer to the steel box beam.By changing the section size of coupling beam,the position of plastic hinge can be controlled.The thickness of the endplate of corbel joints and the front endplate of extended endplate joints has little influence on the joint performance.The thickness of the front plate of corbel joints and the endplate of the extended endplate joints have great influence on the joint performance.When the plate thickness is different,the bearing capacity curve of the joints is often quite different.