Beam-to-column connections adjoining plastic hinges in beams are required to be designed for the overstrength plastic moment of the beam and the associated equilibrium shear force. Three factors influence this overstrength plastic moment in the beam, namely uncertainty in yield stress of steel, effect of strain-hardening on the beam cross-section, and local instability of the beam flanges and web due to slenderness. The effect of strain-hardening is different in non-seismic and seismic moment frames due to different plastic rotation demands on them. This paper presents an explicit procedure for the capacity design of welded beam-to-column connections, which accounts for the expected strain hardening for any desired level of plastic rotation. An idealised shear-moment interaction boundary is used as a guide to estimate the maximum probable bending moment expected to be developed in the beam during strong earthquake shaking, and a step-wise procedure for design of a beam-to-column moment connection is presented through a specific example of a cover-plated and ribbed connection.
Jaswant N. Arlekar, PhD Civil/Structural Engineer, Bechtel Power Corporation, Frederick, MD, USA
Prof. C. V. R. Murty, Dept of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur, India 208016