Formulas: design of members for flexure

Formula 1

For all cross sections covered in Chapter F, the highest possible nominal flexural strength is the plastic moment, $M_{n}=M_{p}$.

Formula 2

For $C_{b}$ greater than 1.0, members with larger unbraced lengths can reach $M_{p}$, as shown by the dashed curve for $C_{b}>1.0$ in Figure C-F1.2.

Formula 3

| Slenderness ($\lambda = b_f / 2t_f$) | Nominal Flexural Strength ($M_n$) | Flange Classification |

Formula 4

| $\lambda_{pf} = 0.38 \sqrt{E/F_y}$ | $M_p$ | Compact flange boundary |

Formula 5

| $\lambda_{pf} < \lambda < \lambda_{rf}$ | $M_p - (M_p - 0.7 F_y S_x \frac{\lambda - \lambda_{pf}}{\lambda_{rf} - \lambda_{pf}}$) | Noncompact flange (Linear transition) |

Formula 6

| $\lambda_{rf} = 1.0 \sqrt{E/F_y}$ | $0.7 F_y S_x$ | Noncompact flange boundary |

Found in

• DESIGN OF MEMBERS FOR FLEXURE