Seismic behavior study on RC-beam to CFST-column non-welding joints in field construction

A newly developed reinforced concrete (RC) beam to concrete-filled steel tube (CFST) column joint without welding in the construction field is introduced in this paper. The seismic experiment is conducted on the joint, and the hysteretic curve of the specimen under cyclic loading on the top of the column is obtained. By analyzing the mechanical characteristics and the failure mode of the joint, a three-stage skeleton curve model is presented. In the elastic stage, the initial stiffness is evaluated by solving the stiffness matrix. In the perfect plastic stage and strength degradation stage, the ultimate strength and the degradation stiffness of the joint can be obtained with the limit equilibrium method. Moreover, the test is also simulated with FEM, and the results agree well with the skeleton curves obtained from the test. So this joint shows good ductility and the ability to dissipate energy, and it can be used to replace the joints welded with reinforcement on the outer annular plate. And the finite element analysis results are compared with the theoretical results, which verifies the theoretical model presented above. It is suggested that the three-stage skeleton curve model can be used to depict the mechanical behavior and bearing capacity of this new type of joint. In addition, Parametric analysis is conducted on this joint, with the consideration of different designs of beams, columns and steel brackets, and failure mode is discussed.