Design of Split-Tee Connections for Special Composite Moment Frames

The beam-to-column connections of special composite moment frames (C-SMFs) serving as the primary seismic force resisting system (SFRS) of a building structure are required to meet the performance criteria specified in the 2010 AISC Seismic Provisions. Chapter K of the Seismic Provisions states that experimental results should be used to provide evidence that the specific beam-to-column connection satisfies the requirements for strength and story-drift angle. This paper focuses on the split-tee connection for C-SMFs with wide flange (WF) beams and rectangular concrete-filled tube (CFT) columns. The paper provides a general description of the split-tee connection identifying its key features and components. This is followed by discussion of expected behavior in the elastic and inelastic ranges of cyclic loading. This discussion is based on prior research and large-scale testing, and it focuses on the various limit states controlling the strength and deformation capacity of the connection. The paper includes the complete design procedure for split-tee connections along with a detailed design example. The information presented in this paper can be used to create a body of evidence to apply for prequalification of similar split-tee connections in C-SMFs.