Should I Use ACI 318 or LRFD for Designing Composite Columns?

Abstract

Steel-concrete composite columns may be designed either by requirements of the American Concrete Institute Building Code ACI 318-99 or by the American Institute of Steel Construction Specifications for Load and Resistance Factor Design, 2nd Edition (1995). Each design standard is described for application to a concrete filled steel tube and to a concrete encased structural shape as each is designed for the same dimensional and service load conditions. These "standard" type column sections are used for the comparison, as the LRFD specification can be used directly only for such standard sections. The design exercise demonstrates that (a) the LRFD specification requires fewer computational steps and is therefore easier to apply, (b) the ACI rules tend to exaggerate the influence of slenderness, and (c) different but very similar results were obtained for the two methods applied to the same design problem.