Test Research On The Behavior Of The Penetration Connections Between Composite Beams And Concrete Filled Tubular Columns

The composite beam and CFT columns frame system has a wide application prospect, while the construction and the mechanical state of the moment-resisting connection are very complicated. The current domestic and foreign design codes have not yet make any design instructions about the connection between composite beams and CFT columns, while some relevant researches are concentrated on stiffening rings connections and inner diaphragm joints and no researches on penetration connections between composite beams and CFT columns at all. As a result, a new type of connection which is penetration connection between composite beams and CFT columns is enhanced to be discussed. To decrease the influence on the core concrete, we weakened the steel beam’s flange before being penetrated to the CFT column.Static load test and low cyclic load test on four different weaken degree connections are performed to discuss the connection’s static behavior and the seismic behavior. The test result infers as follow.The shear forces of the penetration connection between composite beams and CFT columns is transmitted to the core CFT column through the penetration steel beam, while the moment is transmitted to the core CFT column through the main bar in the concrete bar and the bottom flange of the steel beam. The failure of the connection appears on the composite beam is8-12cm away from the column, which is proved to be a bending failure of the composite beam. The static bearing capacity, rigidity, ductility are all very large, but with a decrease as the steel beam’weakens.The load-displacement hysteresis curve and moment-rotation angle hysteresis curve of the penetration connections between composite beams and CFT columns are plump that proved good hysteresis behavior. The displacement ductility and rotation ductility are good, while the energy dissipation coefficient is very large, which are all proved a good seismic behavior for the connection. On the contrast, the ductility, rigidity, energy dissipation ability all decrease as the steel beam’flange weakened, and those decreased quite a lot after0.4weakens.Considered the static and seismic behavior, we suggest that the upper steel beam flange weaken as large and the penetration degree of the steel beam keep1～0.7.