Experimental and Theoretical Study on Cold-Formed Steel Box Stub Columns Under Uniaxial Compression

Abstract

Compression tests were carried out on pin-ended cold-formed steel box stub columns subjected to uniaxial moments. Twenty stub columns with flat width-to-thickness ratio less than the limiting value and twenty stub columns with flat width-to-thickness ratio greater than the limiting value was tested up to collapse. The effect of shape, flat width-to-thickness ratio, slenderness ratio and the eccentricity of loading on the ultimate load-carrying capacity of the box stub columns were studied. It was observed that AISC method of estimating the ultimate load is conservative. Load versus axial shortening behaviour, load versus lateral deflection behaviour and load versus strain behaviour were also studied. The change in eccentricity from r_min/4 to r_min/2 decreases the ultimate load-carrying capacity by 15% for square box stub columns and 20% for rectangular box stub columns in uniaxial loading and increase in slenderness ratio from 15 to 20 does not significantly reduce the ultimate load-carrying capacity. The change in flat width-to-thickness ratio for less than the limiting to a greater extent is uneconomical for both square and rectangular sections with side ratios of 1:1.5 and 1:2. Initial stiffness was more for columns loaded with an eccentricity along major axis. There was reversal of strain from compression to tension for rectangular box columns beyond 75% of ultimate load.