Experimental Investigation of the Cyclic Behavior of Concrete Frame Joints Reinforced with Double-Headed Studs

Current ACI and CSA code provisions recommend large amount of shear reinforcement for concrete frame joints in the form of closed hoops and cross ties to ensure confinement of the joint core. This reinforcement, along with the bends required for anchoring the beam bars, lead to significant congestion within the joint. Double-headed studs are proposed as shear reinforcement in lieu of conventional closed hoops and cross ties. Five full-scale frame joint specimens were tested under cyclic loading. One control specimen was designed without shear reinforcement within the joint. Another control specimen was reinforced with closed hoops and cross ties in the joint according to the Canadian Code provisions. The joints of the remaining three specimens were reinforced with two different arrangements and amounts of double-headed studs. In comparison with the joint without shear reinforcement, the specimens reinforced with headed studs exhibited considerable enhancement in the behavior, in terms of strength, ductility, and energy dissipation.