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Steel Interchange


Double-Angle Compression Member
The term rib in Equation E6-2 of the AISC 360-05 Specification is defined as “radius of gyration of individual component relative to its centroidal axis parallel to member axis of buckling.” Does this mean that rib will be equal to rx of individual angle for LLBB angles, while it is equal to ry of the individual angle for SLBB angles?

Answer

No. I presume that since you are evaluating a built-up angle member with an LLBB configuration, the bolts are through the long legs. These bolts will be subjected to shear when the built-up member buckles about the Y-axis, which lies in the plane between teh long legs. Thus, Rib is equal to ry of the individual angle, since that angle axis is parallel to the Y-axis of the built-up member.

 

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


Posted on July 1, 2010


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