Formulas: Lateral-Torsional Buckling

Equation F5-2

M_{n}=R_{p g} F_{c r} S_{x c}

(a) When $L_{b} \leq L_{p}$ , the limit state of lateral-torsional buckling does not apply.

L_{b} \leq L_{p}

(b) When $L_{p}<L_{b} \leq L_{r}$

L_{p}<L_{b} \leq L_{r}

F_{c r}=C_{b}\left|F_{y}-\left(0.3 F_{y}\right)\left(\frac{L_{b}-L_{p}}{L_{r}-L_{p}}\right)\right| \leq F_{y}

L_{b}>L_{r}

L_{r}=\pi r_{t} \sqrt{\frac{E}{0.7 F_{y}}}

R_{p g}=1-\frac{a_{w}}{1,200+300 a_{w}}\left(\frac{h_{c}-5.7}{t_{w}} \sqrt{\frac{E}{F_{y}}}\right) \leq 1.0