Test And Analysis On Joint Between Concrete-filled Steel Tubular Column And Steel Beam

In recent years, the concrete-filled steel tubular structures have been gradually adopted in high-rise buildings, and have achieved a fast development. As we know that joint is a key technical problem in design process. It will be useful for the popularization of the CFST to understand the behavior of the joint between the concrete-filled steel tubular column and the steel beam.In this paper, the past theory analysis and experiment results have been tallied up systematically, then according to the demand of the research, a series of certain experiments have been completed.Firstly, the mechanical property of the general CFST itself has been analyzed simply in theory. Because of the difference of the Poisson ratio between the steel and the concrete, the wall of the concrete-filled steel tubular will be in tension when the concentrate force exceeds the specific value. At the same time the core concrete will be in three-dimensional stress state. Based on the principle which has said above, the load-carrying ability of the concrete-filled steel tubular structures will be improved greatly. The mechanical behaviors of the specific CFST in this experiment have been discussed subsequently, and this paper put forward the effective height of the wall. Generally speaking, the effective height of the wall is limited to 100mm.Subsequently, the high stress areas and the stress distribution of the joint have been found out by handling and analyzing the large quantity data. For the sake of obtaining the continuous stress distribution of the joint, the numerical computing has been also fulfilled. It is found that no matter what the unidirectional loading or the bidirectional loading the stress at the striking angle of the ring-flat plate is far greater than other areas. Obviously, the high stress is due to stress concentration. For so many reasons above, it is necessary to attach great importance to the design of the striking angle of the ring-flat plate. Naturally one of the best ways to reduce the stress concentration is increase the radian of the striking angle.Secondly, the rigidity of the joint is another key problem in this paper. Based on the means of deflection, the rigidity of the joint has been judged by fitting curve line gained from a large quantity experimental data and the criteria for judging the rigidity of the joint has been also obtained.Finally, the pilot study of the seismic behavior of the joint has been achieved in thispaper. Based on the experimental results, the hysteresis loops under reversed cyclic loads has been depicted. In addition, the failure mode of the joint has been also discussed because it has the important relation with the general seismic design principle. From which it has been shown that the static strength and the rigid of the joint put forward in this paper satisfy the design demand. By analyzing some seismic indexes and the failure mode of the join, it has discussed the seismic behavior of the joint. In terms of its principal indexes of the ductility and the energy dissipation, the seismic behavior of the joint is good. While the only flaw of the joint is its failure mode under reversed cyclic loads, because of which the seismic behavior of the joint is insufficient.From what discussed above it suggests that the striking angle of the ring-flat plate be design carefully. Concretely, the radian of the striking angle must be increases and the quality of the weld should be assured, furthermore the thickness of the wall which is adjacent to the joint must be increased too. By the measures suggested above the strength of the joint can be strengthened, but whether the plastic hinge can be occurred at the end of beam is an uncertain problem.