Figure 2 shows the cross-section of a thin-walled beam. The thickness of the walls is constant throughout. AS, JR 3 a't Sin B 12 1.5 mm 1.5 mm (b) Give the definition of shear centre. Total 1.5 mm 6 60 mm Figure 2: cross-section of a thin-walled beam. 1, -a't Cos B, 1 = 24 12 5 17 mm (a) Calculate the position of the shear centre from wall 3-4 (i.e. 5) of the thin- walled section shown in Fig. 2. 15 mm 30 mm To calculate the second moments of area of the inclined walls, use the following expressions. ta' Sin2 B I 24