Experimental investigation of new internal-diaphragm connections to CFT columns under cyclic loading

• Tests on full-scale specimens of new internal-diaphragm connections to CFT columns.
• Beam failure modes dominate.
• Stable and plentiful hysteresis behavior is characterized.
• Tapered plates alleviate strain concentration.
• The connections meet the requirement for composite intermediate moment frames.

The seismic performance of a new internal-diaphragm connection is investigated in this study. The new connection effectively alleviates the stress and strain concentration at the beam-ends and largely moves the plastic hinges away from the column face by utilizing horizontal stiffeners to form tapered beam flanges. This paper reports on an investigation into the cyclic behavior of internal-diaphragm connections to concrete filled tubular (CFT) columns using tapered plates. Two full-scale connections were tested under quasi-static cyclic loading. The strength, stiffness, deformation, ductility, energy dissipation capacity and strain distribution were evaluated at different load cycles. It is shown that the connection configuration provided stable hysteresis behavior with appropriate level of strength and stiffness. The results indicate that this connection can offer ductility and energy dissipation capacity appropriate for its potential application in composite intermediate moment frames in seismic region.