A viewing platform in a wild-animal park (following figure 1) is supported by a row of aluminum pipe columns having length L = 3.25 m and outer diameter d =

100mm. The bases of the columns are set in concrete footings and the top of the columns are supported laterally by the platform. The columns are being designed to support compressive loads P = 100KN. Determine the minimum required thickness t of the column if a factor of safety n = 3 is required with respect to Euler buckling. Based on the calculated thickness, find the critical stress in the column and check if that is less/more than the proportional limit. Use: E = 72 GPa for the modulus of elasticity and 480 MPa for the proportional limit.