Analysis And Research On Behavior Of Connections For Concrete-Filled Steel Tube Column To Beam Frames

Concrete filled steel tubular structure is a type of new structure that can make the best of steel and concrete. Owing to its good behavior, the new structure is used more and more widely by engineering devisers and developers. On the other hand, due to the diversity of connections and their complex approaches in transferring forces, no applied and effective method to judge the behavior of connections has been found. Therefore, there is some differences in some aspects, such as the analysis method of force, estimate of structural behavior under earthquake and design of connections conformation. Based on the above-mentioned, both theoretic and experimental methods are used to analyze the tectonic, initial rigidity and local mechanics performance of connections. Moreover, criterion to distinguish the rigid connection, semi-rigid connection and flexible connection is discussed in this paper.Results can be obtained from theoretic analysis in practice. The results show that the shearing force in the end of beam can be transferred to concrete-filled steel tube effectively by the connections. However, there are some differences about moment transfer among different connections in the end of beam. Steel stiffening ring, steel corbel and reinforcing concrete hoop-beam are commonly used to transfer the moment in end of beam. Although abundant researches are carried through to discuss the capacity of connections, no agreement is come on the compute mode. The main reason is that no systemic research is processed on the rigidity of connections.Mechanics mode composed of lots of series-parallel connection springs is adopted to not only simulate the steel stiffening ring connection but deduced a formula to calculate initial rigidity of connection. Compared to the result of analysis in FEA, the theoretic formula can coincide well with FEA.ANSYS is employed to analyze the performance of steel stiffening ring. Conclusions can be draw that the wider steel stiffening is, the less rigid the performance is. At the same time, the width of beam is an important factor to decide the rigidity of connection. Three specimens of connection for concrete-filled steel tube column to WF steel beam are tested to failure using monotone static test method. Steel stiffening ring connection takes on little distortion even when the steel beam fails. In other words, the connection has a high rigidity. At the same time, the ring can reinforce the joint core and strengthen the connection. In addition, the ribbing can transfer shear force in the end of beam effectively and ensure other components working jointly. The torsion of beam plays an important influence on the rigidity of connection. Slab will restrict the torsion of beam and minimize the adverse effect in practical engineering. Finally, tolerance and disfigurement of steel components have some effects on the behavior of connection. Measures should be taken to control the influence.By virtue of the analysis of rigid frame and semi-rigid frame, a criterion to distinguish the rigid connection, semi-rigid connection and flexible connection is proposed. Moreover, primary discuss is executed to probe the design method of semi-rigid frame by theoretical analysis.