Load Capacity of Nested, Laterally Braced, Cold-Formed Steel Z-Section Beams

Cold-formed steel Z-purlins were tested in combining bending and shear to evaluate the behavior of lap joints. The tested sections covered a range of web depth-to-thickness ratios ( h /t) from 79 to 131 and lap-to-span ratios from 0.25 to 1.0. The results indicated that the lapping process significantly enhances the load capacity for beams with lap-to-span ratios up to 0.5. Little or no further enhancement was noted for higher ratios. A bending buckling pattern governed the failure of all beams at stresses close to the steel yield stress. Failure was encountered in the single-section zone for beams with lap-to-span ratio less than 0.5, and in the lap zone for higher ratios. Correlations were established to predict the load capacity of lapped beams and were found in agreement with the results of a study cited in the literature. Current American Iron and Steel Institute specifications were also found to be adequate to predict the strength of the single Z-section.