P5 The figure shows the cross-section of a thin-walled beam in the form of a

channel with lipped flanges. The lips are of constant thickness 1.27mm, while

the flanges increase linearly in thickness from 1.27mm where they meet the

lips to 2.54mm at their junctions with the web. The web has a constant

thickness of 2.54mm. The shear modulus G 26700MPa throughout. The

beam has an enforced axis of twist RR and is supported in such a way that

warping occurs freely but is zero at the mid-point of the web. If the beam

carries a torque of 100Nm, calculate the maximum shear stress according to

the theory of torsion for thin-walled sections. Ignore any effects of stress

concentration at the corners. Skip the distribution of warping.