An I-section with flanges 60 mm X 6 mm and web 168mm X 3.6mm is subjected to a twisting moment of 0.24 kNm. Find the maximum shear stress and twist per unit length neglecting stress concentration. G=80000 N/mm. In order to reduce the stress and the angle of twist per unit length, the I-section is reinforced by welding steel plates 168 mm X 6mm parallel to the web and at the ends of flanges. Find the maximum shear stress due to same twisting moment and also the value of angle of twist per unit length.