Experimental Study of Rigid Connection of Beam to Concrete-Filled Tube Column with Stiffened Internal Diaphragm

Concrete-filled tube (CFT) columns are a favorable and economical option for designing mid-height and tall buildings. However, using internal continuity plates in conventional moment frames will weaken the panel zone since infill concrete is present inside the steel tube column. Due to perforation of the continuity plate, stress distribution in this plate changes, and its strength and stiffness decrease. The proposed method in this study is aimed to strengthen the continuity plates with shear stud so as to transfer a part of the high force of continuity plates to the concrete. In this regard, two different full-scale specimens of rigid connections of I-shaped beam to CFT column were tested under cyclic loading. In the other part, using the finite element method in Abaqus software, the experimental specimens were modeled and analyzed. As a result of the stiffening of the continuity plates, the connection's bending capacity and cumulative dissipated energy increased by 7% and 4%, respectively. Additionally, the stiffening moved the highest rupture index by approximately 20% of the beam flange width from the outer edge of the flanges of the beam to the longitudinal axis of the beam. The proposed connection was approved for use in seismic zones' intermediate moment frames.