PROBLEM $3$: A tubular post of square cross section supports a horizontal platform. The

tube has outer dimension $b=6$ in$.$ and wall thickness $t=0\mathrm{.}5$ in$.$ The platform has

dimensions $6\mathrm{.}75$ in $x24\mathrm{.}0$ in and supports the load as shown.

$[1]$ Calculate the normal stress at A and indicate if compression or tension.

$[2]$ Calculate the normal stress at $B$ and indicate if compression or tension.

$[3]$ Calculate the shear stress at $B.$

$[4]$ Calculate the maximum in$-$plane shear stress at A$.($Hint: use Mohr's circle$)$

$[5]$ Calculate the principal stresses at B$.($Hint: use Mohr's circle$)$

ANS: $[1]4090$ psi $($C$),[2]1860$ psi, $[3]162\mathrm{.}74$ psi, $[4]2050$ psi, $[5]14\mathrm{.}14$ psi and $-1874\mathrm{.}13$

psi