High-Strength Reinforcement in Exterior Beam-Column Joints under Cyclic Loading

This paper presents cyclic responses of five exterior beam-column joints made with 100 ksi (690 MPa) longitudinal bars, 115 ksi (790 MPa) transverse reinforcement, and 10 ksi (70 MPa) concrete. The test joints satisfied the existing ACI 318 design provisions for special moment frames, except for the joint shear demands, the anchorage limitations of the maximum bar yield strength, the maximum concrete strength, and the minimum clear spacing between headed bars. The test results show that the minimum development length can be used for anchorage of closely spaced headed bars in well-confined joints. It is found that the deformation capacity of beam-column joints could be increased by reducing the joint shear demand or increasing the joint transverse reinforcement ratio. The presented test results were assembled with previous research data for assessing the design provisions. This paper proposes several modifications to the existing design provisions for beam-column joints using high-strength reinforcement and concrete.