Buckling Strength of Single Angle Compression Members in K-Series Joists

Abstract

Single angle web members in open web steel joists are typically crimped to facilitate web placement and maintain a constant chord gap with varying web angle size. If the web members are not crimped force eccentricity will exist between the web member's area centroid and the vertical plane of symmetry for the joist. The analytical consequence of this eccentricity is that uncrimped single angle web members must be designed as eccentrically loaded columns. The resulting interaction design strength is significantly less than the concentric column analysis design strength used for crimped web members of identical cross section and slenderness. This study compares the measured and analytical strengths of like single angle L1x1x7/64 inch crimped and uncrimped web members in steel joists. Experimental results from 18 joist samples show that existing analytical assumptions associated with end fixity and beam-column interaction result in an overly conservative design methodology for both crimped and uncrimped web members.