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Title: Simplified Design Equation of Minimum Interior Joint Depth for Special Moment Frames with High-Strength Reinforcement

Author(s): Hung-Jen Lee,Hsi-Ching Chen,Tsung-Chieh Tsai,

Publication: IJCSM

Volume: 12


Appears on pages(s):

Keywords: beam-column joint, bond, cyclic testing, high-strength reinforcement, slip

DOI: https://doi.org/10.1186/s40069-018-0303-2

Date: 11/30/2018

To avoid excessive slip of beam longitudinal bars at the joints of an earthquake-resisting moment frame, ACI 318 Building Code set a minimum joint depth of 20 times the diameter of the largest longitudinal beam bars passing through the joint, which is based on prior experimental verification of beam-column joints with Grade 420 MPa reinforcement. In view of that the 20-bar-diameter criterion cannot be simply extended for concrete frame joints with higher grade reinforcement, this paper summarizes international existing design criteria and proposes a simplified equation for the minimum joint depth. The equation applicability is assessed by evaluating the cyclic testing results of beam-column joints conducted in East Asian and Pacific Countries, where Grade 490, 590, and 690 MPa reinforcement have been used for earthquake-resistant concrete structures. Beam-column joints that satisfy the proposed equation can demonstrate satisfactory hysteresis behavior at an interstory drift of 4%.