Elastoplastic behavior of through-diaphragm connections to concrete-filled rectangular steel tubular columns

• Two mechanical models were proposed to predict flexural and shear strength of the through-diaphragm connection.
• The influence of axial force was explored on the contribution of both steel tube and through-diaphragm.
• The contribution of steel frame mechanism was taken into account.
• Modification has been made to the principal compression angle of the concrete core.
• A theoretical method for evaluating the shear strength of the concrete compression struct at the yielding was presented.

Two analytical models are presented to predict the flexural and shear strengths of through-diaphragm connections between concrete-filled rectangular steel tubular (CFRST) columns and steel beams, respectively. The first phase of this research program was to assess the moment transfer mechanism at the through-diaphragm connections using the analytical yield line method, which accounts for the influence of the axial load on the moment transfer in panel zone. The use of the proposed theoretical equations led to good agreement between predicted and experimentally measured strength. As the second phase of the research program, an analytical model for shear strength was presented according to the simplified trilinear shear–deformation relationship for connections. A theoretical method was proposed to evaluate the shear strength of the concrete compression strut at the yielding point of the steel tube. In addition, the contribution of steel frame mechanism in the panel zone was taken into account in the proposed model. Excellent agreement was found between theoretical and experimental results for both yield and ultimate shear strengths for connections.