The optimum depth of a plate girder is given by the following expression:
1
\( {\left( {\frac{{Mk}}{{{f_y}}}} \right)^{1/3}}\)
2
\({\left( {\frac{M}{{{f_y}{k^2}}}} \right)^{2/3}}\)
3
\({\left( {\frac{{M{k^2}}}{{{f_y}}}} \right)^{1/3}}\)
4
\({\left( {\frac{{M{k^2}}}{{{f_y}}}} \right)^{4/3}}\)