Research On Hysteretic Behaviour Of The Connection Between Steel Tube-reinforced Concrete Column And RC Beams

Steel tube-reinforced concrete (STRC) column has been gradually applied to bridges and building structures for its high strength, good ductility and good fire resistant property. Meanwhile, the reinforced concrete (RC) beam has been widely used in building structures. However, the connection between column and beam is the key part of the building structure. Thus, it is necessary to study the behaviours of STRC column and RC beam joints. In this paper, the experimental and finite element (FE) studies were used to study the seismic performance of this kind of connection. The main research works were summarized as follows:(1)This paper systemically summarized the current situation of the relevant research at home and abroad and fully demonstrated the necessity of this research.(2) Four joints between STRC column and RC beam were tested under cycle loading. All these specimens were tested under axial force and lateral reverse cyclic loading which were applied on the top of the column and the end of beams respectively. The main parameters were axial compression ratio and whether working with concrete floor. Based on these test results, the influences of these parameters on seismic behaviours were discussed so that a quantitative estimation on the seismic behavior could be concluded. The result showed that the load versus displacement curve of this kind of connection was plump. Stable strength and stiffness degradations were also observed. The failure models were all flexural failure at the end of beams. Thus, it can be concluded that this kind of joints had a good seismic performance.(3) FE models were established. The effect of the material nonlinearity, the geometric nonlinearity, the concrete damage, the interaction between the steel tube and concrete, the bond performance of steel bars and concrete, Baugtsziger effect, the unloading stiffness degradation of steel bars were fully considered in this FE model. The correctness and effectiveness of the model have been verified by the tests in this paper. Based on this FE model, the working mechanism of this connection was also analyzed.(4) Based on this FE model, a large number of parameters analysis were carried out. The parameters included the strength of core concrete, the width of the external reinforcing ring, the strength of the hidden corbel, the length of the hidden corbel, the width of the RC slab, the reinforcement rate of the RC slab, the axial load ratio of the column and the flexural bearing capacity of RC beam. The study showed that the key factors which affect the hysteretic behaviour of this kind of joint were the axial load ratio of the column and the flexural bearing capacity of RC beam, while other factors had relatively little effect.