The optimum thickness of web, tw, of a plate girder is given by
1
\( t_w = \left [ \frac{M_z{}}{f_y{k^{2}}} \right ]^{0.33}\)
2
\(t_w=\left [ \frac{f_y{k^2{}}}{M_z{}} \right ]^{0.33}\)
3
\(t_w=\left [ \frac{M_z{}}{f_y{k^2{}}} \right ]\)
4
\(t_w=\left [ \frac{f_y{k^2{}}}{M_z{}} \right ]\)