Experimental investigation on built-up columns

This study presents a direct experimental verification of the AISC-LRFD slenderness ratio formulas for built-up compression members. Comparisons of slenderness ratios as specified in various design codes including the AISC-ASD, the AISC-LRFD, the AS-4100 and the CSA S16-01, are also provided. Test results concluded from this study show that the 1999 LRFD formulas generally result in conservative design strengths. However, the 2005 LRFD yields slightly higher strength due to the use of a higher resistance factor of 0.9 instead of 0.85. The design strengths determined based on the slenderness ratio formulas of the Australian Code (AS-4100) are even more conservative. For back-to-back snug-tight bolted sections, the Canadian Code (CSA S16-01) gives virtually the same design outcome as the LRFD. While for back-to-back welded sections, the CSA S16-01 tends to yield a less conservative design.