Tests on Built-Up Columns of Structural Aluminum Alloys

Results from tests on fifteen built-up column specimens of structural aluminum alloys and on two of structural steel are presented in this paper. The investigation was a study of the effect of the shape of section on the strength of built-up columns. All specimens had maximum slenderness ratios of about 40 and cross-section areas of 7 or 8 sq in. Strains and deflections were measured under various loading conditions. In the range of working lo ads the shape of the cross-section has no significant effect on the ratio of the measured to computed deflections of the axis of the specimen nor on the magnitude of the transverse shear indicated by the· l acing-bar stresses. The shape of the cross-section has a significant effect on the ratio of the measured to computed stresses, the local deflections under higher loads, and on the type of failure, whether by buckling of a component part or by bending as a unit. Short built-up columns of high-strength aluminum alloys are likely to fail by local buckling at average stresses less than the yield strength of the material when the width-to-thickness ratio of outstanding plates and legs of angles exceeds about 12 and when the width-to-thickness ratio of the cover-plates exceeds about 40.