Effect of column flange flexibility on WF-beam to rectangular CFT column connections

• Out-of-plane deformation of column flange was studied.
• Out-of-plane deformation of column flange influenced shear and flexural stress distribution.
• Poisson effect and out-of-plane deformation influenced shear flow at beam end.
• Low transfer efficiency of beam web induced larger force transferred by beam flange.
• A moment evaluation method based on the out-of-plane deformation was presented.

Researches in the United States discovered different tension and shear flow patterns between wide flange (WF) column connections and box column connections. On the other hand, researches in Japan started many research on flexibility of column flange and proposed connection flexural moment strength based on the out-of-plane deformation for hollow section box column connections. However, both force flow pattern research and out-of-plane influence study in WF beam to rectangular concrete filled tube (CFT) column connections are insufficient. While due to the different composition and geometry configuration, direct extension of previous results is not feasible. This paper discusses the out-of-plane deformation at column flange, force flow pattern and shear and moment transfer efficiency of WF-beam to rectangular CFT column connection. Results show that both Poisson effect and flexibility of column flange will lead to a change on force flow pattern in beam–column junction region and inefficient moment transferring ability through beam web, resulting in a high level of hydrostatic stress demand at beam flanges. Weld access hole, thickness of column flange and diaphragm and web connection details all have certain effect on column flange bending stiffness and the transfer efficiency of beam web. A flexural strength evaluating method for the rectangular CFT column connection based on the out-of-plane deformation is also presented.