The sign is $\backslash (3\backslash$mathrm$\{$~m$\}\backslash$times $2\backslash$mathrm$\{$~m$\}\backslash )$ and will be subjected to a wind pressure of $0\mathrm{.}7$ kPa $($see Fig. $\backslash (1(\backslash$mathrm$\{$a$\})\backslash )).$ The sign is connected to a $10$ m high support column which will be a circular hollow steel tube of unknown diameter $\backslash ($ D $\backslash )($Fig$.$ l$($b$)).$

The steel has the following properties:

Tensile yield strength $\backslash (=350\backslash$mathrm$\{$MPa$\}\backslash )$

Shear strength $\backslash (=60\backslash \%\backslash )$ of tensile strength

Elastic shear modulus $\backslash (=70\backslash$mathrm$\{$GPa$\}\backslash )$

The thickness of the tube is $\backslash (5\backslash \%\backslash )$ of the diameter.