Formulas: Doubly and Singly Symmetric Members Subjected to Flexure and Compression

Formula 1

(a) When $\frac{P_{r}}{P_{c}} \geq 0.2$

\frac{P_{r}}{P_{c}} \geq 0.2

\frac{P_{r}}{P_{c}}+\frac{8}{9}\left(\frac{M_{r x}}{M_{c x}}+\frac{M_{r y}}{M_{c y}}\right) \leq 1.0

(b) When $\frac{P_{r}}{P_{c}}<0.2$

\frac{P_{r}}{P_{c}}<0.2

\frac{P_{r}}{2 P_{c}}+\left(\frac{M_{r x}}{M_{c x}}+\frac{M_{r y}}{M_{c y}}\right) \leq 1.0

where

$\begin{aligned} P_{r} & =\text { required compressive strength, determined in accordance with Chapter C, } \\ & \text { using LRFD or ASD load combinations, kips (N) }\end{aligned}$
$P_{c}=$ available compressive strength, $\phi_{c} P_{n}$ or $P_{n} / \Omega_{c}$ , determined in accordance with Chapter E, kips (N)
$M_{r}=$ required flexural strength, determined in accordance with Chapter C, using LRFD or ASD load combinations, kip-in. (N-mm)
$M_{c}=$ available flexural strength, $\phi_{b} M_{n}$ or $M_{n} / \Omega_{b}$ , determined in accordance with Chapter F, kip-in. (N-mm)
$x \quad=$ subscript relating symbol to major-axis bending
y = subscript relating symbol to minor-axis bending