Q$4)$ Fig. $1$ shows a two$-$cell tubular section whose wall thickness are as shown. If the member is subjected to a torque T$,$ determine the shear flows and the angle of twist of the member per unit length in terms of section parameters; side of member $\text{'}a\text{'}$ and thickness $\text{'}t\text{'}.$

If applied torque $T=10000Nm$; side of member $\text{'}$ a $\text{'}=100mm$ and thickness $\text{'}t\text{'}=10mm,$ find shear flows and the angle of twist of the member per unit length.

$[10]$

Fig. $1($Q$4)$