Design for Shear of Prestressed Concrete Beam-Column Joint Cores

Reversed cyclic loading tests of eight prestressed and two nonprestressed concrete exterior beam-column joint assemblies that failed inside the joint cores were conducted. The test results revealed no significant difference in the maximum story shear force between the prestressed and nonprestressed concrete test units although the horizontal input shear forces of the joint cores at the maximum story shear forces of the prestressed concrete units (calculated based on the column shear force and the forces in the reinforcing and the prestressing steels) were greater than those of the nonprestressed concrete units. On the basis of this result, the writers have concluded that prestressing force does not play a major role on the ultimate shear strength of beam-column joint cores. In addition, the design shear force acting on a beam-column joint core should be determined using the average shear force calculated from the bending moment at the beam-column interfaces, not by the horizontal input shear force. These conclusions led the writers to develop design equations for estimating design shear forces and ultimate shear capacities of prestressed concrete interior and corner joints. The equations were compared with test data on 51 beam-column joint assemblies that failed in shear in the joint cores. The test results agreed well with the estimations.