Structural Cross Sections

Appendix B

Torsional Constant Factors

$K=K_1+K_2+\alpha D^4$
$K_1=h{b_{\mathrm{w}}}^3\left[\frac{1}{3}-0.21\frac{b_{\mathrm{w}}}{h}\left(1-\frac{{b_{\mathrm{w}}}^4}{12h^4}\right)\right]$
$K_2=\left(b_{\mathrm{f}}-b_{\mathrm{w}}\right){h_{\mathrm{f}}}^3\left[\frac{1}{3}-0.105\frac{h_{\mathrm{f}}}{\left(b_{\mathrm{f}}-b_{\mathrm{w}}\right)}\left(1-\frac{{h_{\mathrm{f}}}^4}{192{\left(b_{\mathrm{f}}-b_{\mathrm{w}}\right)}^4}\right)\right]$
$\alpha =0.07\frac{h_{\mathrm{f}}}{b_{\mathrm{w}}}$

$K=K_1+K_2+\alpha D^4$
$K_1=b_{\mathrm{f}}{h_{\mathrm{f}}}^3\left[\frac{1}{3}-0.21\frac{h_{\mathrm{f}}}{b_{\mathrm{f}}}\left(1-\frac{{h_{\mathrm{f}}}^4}{12{b_{\mathrm{f}}}^4}\right)\right]$
$K_2={b_{\mathrm{w}}}^3{h}_{\mathrm{w}}\left[\frac{1}{3}-0.105\frac{b_{\mathrm{w}}}{h_{\mathrm{w}}}\left(1-\frac{{b_{\mathrm{w}}}^4}{192{h_{\mathrm{w}}}^4}\right)\right]$
$\alpha =0.07\frac{t}{}$