The three-cell structure shown below uses stiffeners connected with shear panels. Note that the curved panel between stiffeners 1 and 3 is semi-circular. The structure is under the action of forces and moments as shown. Assume the shear panels do not carry any direct stress. The material properties are: E = 72 GPa, G = 28 GPa, ty = 270 MPa, cy = 240 MPa, y = 170 MPa. The values of a, b, B, D, F are taken from Question 0.
(a) Calculate the shear flow in each panel and determine the critical margin of safety in shear .
(b) Re-size the thickness of the shear panels to reduce the cross-sectional area to achieve the following design requirements : 1. area fraction A/A0 less than 0.30 2. all margins of safety greater than or equal to 0.0 3. no panel thickness less than 0.2015 mm
