Studies On Seismic Behavior Of Steel Beam To Concrete-filled Steel Tubular Column Connections With Through Diaphragms

Concrete-filled steel tubular structure which used in multi-storied buildings can reduce steel quantity and achieve good economic benefits, so as to heavy applications in market. The characters of multi-storied buildings of large column net composed of i-shaped beams and concrete-filled steel tubular columns are large section of beam, thick plate and thin wall of steel pipe. Though, the connections with inner or outer diaphragms both have the problem of welding the thick plate to the thin plate, which may lead to large welding deformation and large welding residual stress, reducing the transfer reliability of the connections. It can be avoided with through diaphragms that the columns broken and welded to the through diaphragms. But the type of connection has not been mentioned in our current specifications. National standards atlas Construction of Concrete-filled Steel Tubular gives the basic construction of the through diaphragms. For the details of the connection construction such as overhanging length of through diaphragms, lacking background information and there is seldom relative research in our country.In the paper, based on a six-storey frame with concrete-filled steel tubular column and 10.8 meters column net, the mechanical behavior of the joints with through diaphragms is investigated by finite element analysis considering monotonic load and cyclic load, and further discussion is carried out regarding the effects of the details on the seismic resistance behavior. The research content and results are presented as follows:1. Finite element modeling for the experimental joints are set up and the comparison between finite element calculations and test results are carried out. It is concluded that finite element modeling can simulate the hysteretic curves and the ultimate load bearing capacity well.2. The joints with through diaphragms of project size are investigated by finite element analysis considering monotonic load and cyclic load. We get a set of data such as the process of plastic zone and hysteresis loops, analyzing the mechanical behavior and destructive process of every parts of the joint, and giving the evaluation of the seismic behavior.3. Based on the joints with through diaphragms of project size, using the shape given by Construction of Concrete-filled Steel Tubular, the finite element modeling set up in order to analyze if the connection with bolt will affect the mechanical behavior of the joint. Give the evaluation of the seismic behavior.4. Design parameter analysis for the joints is carried out through finite element method so as to find out the influence of diaphragm thickness, extend length, axial compression ratio on joint behavior. A few guidelines are suggested for the design of the joints between steel beam and concrete-filled steel tubular columns.5. A few guidelines are suggested for the design of the joints between the steel beams and concrete-filled steel tubular columns.