The following formulas apply to members in which the resultant of all loads acting on a member is an axial load passing through the centroid of the effective section (calculated at the nominal buckling stress Fn, ksi). The axial load should not exceed Pa, kips, calculated from
where K effective length factor
L unbraced length of member, in
r radius of gyration of full, unreduced cross section, in
E modulus of elasticity of the steel, ksi
Moreover, angle sections should be designed for the applied axial load P acting simultaneously with a moment equal to PL/1000 applied about the minor principal axis and causing compression in the tips of the angle legs.
The slenderness ratio KL/ r of all compression members preferably should not exceed 200, except that during construction only, KL/ r preferably should not exceed 300.
For treatment of sections that may be subject to torsional or torsional-flexural buckling, refer to AISI Specification for the Design of Cold-Formed Steel Structural Members, American Iron and Steel Institute, 1101 17th St., NW, Washington, DC 20036.