A sign for an automobile service station is supported by two aluminum poles of hollow circular cross section, as shown in the figure. The poles are being designed to resist a wind pressure of 75lb/ft2 against the full area of the sign. The dimensions of the poles and sign are h1 = 20ft, h2 = 5ft, and b = 10ft. To prevent buckling of the walls of the poles, the thickness is specified as one-tenth the outside diameter d.
(a) Determine the minimum required diameter of the poles based upon an allowable bending stress of 7500 psi in the aluminum.
(b) Determine the minimum required diameter based upon an allowable shear stress of 2000 psi.

Transcribed Image Text:

Wind load 12 10