Where the horizontal stiffeners are provided 'd' in mm shall be taken as a clear distance between the horizontal stiffeners and tension flange. These vertical stiffeners shall be designed so that I is not less than
1
\(1.3 \frac{d^{3} t^{3}}{C^{2}}\)
2
\(1.5 \frac{d^{3} t^{3}}{C^{2}}\)
3
\(0.87 \frac{d^{3} t^{3}}{C^{2}}\)
4
\(0.85 \frac{d^{3} t^{3}}{C^{2}}\)