Experimental Study Of Semi-connected Concrete Filled Steel Tubes - Core Steel Tube Side Node

This article was the further research to the new type of column-beam joint of concrete filled steel tubular (CFST), which Prof Wang yihong presented. Some problems were discovered in this unconnected side column-beam joint. So a new test research was carried out for the improved half-connected side column-beam joint. The character of this improved joint is that the outer steel tube is half-connected in the joint zone, and the without beam side of the steel tube is connected. The other three sides that have beams are notched. The rest settings act in accord with the unconnected side column-beam joint. The static behavior and effects to the joint zone under low-cyclic reversed load of the beam were analyzed to examine the destroyed shape and the mechanism of the joint through 2 improved side column joints. The test indicated that the beam ruptured from its root under low-cyclic reversed load, and the restriction of the joint zone from beams is minished. But the carrying capacity at the joint zone was still higher than the beam and column connected by joint. Comparing the new test results with the former test results, the new test results verified that the half-connected side column-beam joint was better than unconnected side column-beam joint's in the terms of continuity of CFST and the core concrete restriction. The new productions were gained for the series of study on this new type of column-beam joint of concrete filled steel tubular, and it was the advancement based on the unconnected side column-beam joint.The inner mechanism was studied by using nonlinear finite element analysis (FEA) of the side joint specimens. The FEA showed that the potential carrying capacity of the core steel tube of the joint zone was high when beams were destroyed and CFST was close to the limited intension. It accords with the design requirements of "the column is stronger than the beam; the joint is stronger than the frame member". The FEA results concorded with the test results. It verified the rationality and reliability of the new joint design.