F12Unsymmetrical shapes

This section applies to all unsymmetrical shapes except single angles.

The nominal flexural strength, $M_{n}$, shall be the lowest value obtained according to the limit states of yielding (yield moment), lateral-torsional buckling, and local buckling where

(F12-1)

where

$S_{\min }=$ minimum elastic section modulus relative to the axis of bending, in. ${ }^{3}\left(\mathrm{~mm}^{3}\right)$

User Note: The design provisions within this section can be overly conserva- tive for certain shapes, unbraced lengths, and moment diagrams. To improve economy, the provisions of Appendix 1.3 are recommended as an alternative for determining the nominal flexural strength of members of unsymmetrical shape.

F12.1 Yielding

(F12-2)

F12.2 Lateral-Torsional Buckling

(F12-3)

where

$\begin{aligned} F_{c r} & =\text { lateral-torsional buckling stress for the section as determined by analysis, } \\ & \text { ksi (MPa) }\end{aligned}$

User Note: In the case of Z-shaped members, it is recommended that $F_{c r}$ be taken as $0.5 F_{c r}$ of a channel with the same flange and web properties.

F12.3 Local Buckling

F-For SFy (F12-4)

where

$F_{c r}=$ local buckling stress for the section as determined by analysis, ksi (MPa)