MOMENT-ROTATION MODEL OF EXTERNAL COVER PLATE JOINTS BETWEEN STEEL BEAMS AND CONCRETE-FILLED SQUARE STEEL TUBULAR COLUMNS WITH INNER I-SHAPED CFRP PROFILE

As a new type of beam-column joint, external cover plate joints can be used in concrete-filled square steel tubular (CFSST) structures. To accurately analyze the mechanical characteristics of this novel joint during structural design, it is necessary to investigate the moment-rotation relationships. Based on the analysis of the force-transferring mechanism, the formulas to decide the initial rotation stiffness and ultimate bending moment are founded by using the component analysis method, while the finite element analysis results are also utilized to verify these formulas. Considering the advantages and disadvantages of the existing typical moment-rotation models, a new representation for calculating the moment-rotation curve of the external cover plate joints is proposed using the ultimate bending moment and initial rotation stiffness as two basic parameters. The research reveals that the moment-rotation model proposed in this paper is able to take all loading stages of this joint into account, which facilitates the analysis of yield and ultimate loads. In addition, this model is smooth and continuous at the piecewise points to avoid numerical problems that may be caused in the calculation. Comparing the moment-rotation curves obtained by the calculation model and finite element simulation, the results show good consistency, demonstrating that the moment-rotation model presented in this paper is applicable to the analysis and design of the external cover plate joints.