Steel Interchange

Minimum Composite Shear Connection

Answer

This is discussed in the Commentary to Section I3.3 of the 2005 AISC Specification as follows:

“There is no minimum requirement for the amount of shear connection. Design aids in the U.S. often limit partial composite action to a minimum of 25% for practical reasons, but two issues arise with the low degree of partial composite action. First, less than 50% composite action requires large rotations to reach the available flexural strength of the member and can result in very limited ductility after the nominal strength is reached. Second, low composite action results in an early departure from elastic behavior in both the beam and the studs. The current provisions, which are based on ultimate strength concepts, have eliminated checks for ensuring elastic behavior under service load combinations, and this can be an issue if low degrees of partial composite action are used.”

Kurt Gustafson, S.E., P.E.