The Effect of Frame Action on Force Distributions in Concentric Vertical Brace Connections [N55]

Part 13 of the AISC 14th Edition Steel Construction Manual provides free body diagrams of admissible force distributions, based on the Uniform Force method, in concentric vertical braces framing into beam-column joints. At the beam-to-column connection, the axial force taken through the beam end connection is considered to be the sum of the resultant horizontal force acting on the connection (Hc) and the required transfer force. As the joint rotates due to frame action, a distortional force is induced at this location which always acts in the opposite direction of the Hc term, effectively reducing the total axial force acting on the connection. This presentation discusses how to minimize the design axial requirements on the beam end connection by accounting for such frame action.

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