Wide Beam-Column Connections under Earthquake-Type Loading

Wide beam-column connections, whose beams are wider than their supporting columns, are often found in one-way concrete joist systems and in other buildings where floor-to-ceiling heights are restricted. Research into the seismic behavior of these connections stems from the recommendation by ACI-ASCE Committee 352 (Monolithic Connections in R/C Framed Structures) that these connections be evaluated for use in high seismic zones. Four exterior 3/4-scale specimens, including transverse beam with reinforcement, were tested at the University of Michigan Structural Engineering Laboratory. The effects of joint shear stress level, fraction of beam longitudinal reinforcement anchored in the column core, and beam-width to column-width ratios (bw/bc) were explored as part of this research. The experiments show that wide beam-column connections can be used in high seismic zones if they are detailed correctly. If they are not detailed correctly, the exterior connections will be incapable of transferring the plastic hinge bending moments to the column because the transverse beam cracks in torsion. To prevent this cracking of the transverse beam, limits on the torque applied to the transverse beam are proposed.