The figure shows the cross-section of a box girder with overall dimensions given in terms of a in the figure. The thickness of the upper horizontal flange is 2t, while the thickness of the remaining three flanges is t. The cross-section is loaded by a torsion moment Mx. The material is linear elastic with shear modulus G. The cross-section is thin-walled with t « a.
a) Determine the shear flow q in the crosssection.
b) Determine the mean shear stress τm in each of the flanges of the cross-section.
c) Determine the torsion stiffness GK.
![796_87a10533-e36d-457b-8b4a-63a1c0854c4f.png](https://secure.tutorsglobe.com/CMSImages/796_87a10533-e36d-457b-8b4a-63a1c0854c4f.png)