Find the required outside diameter d for a steel pipe column (see figure) of length L =

Question:

Find the required outside diameter d for a steel pipe column (see figure) of length L = 20 ft that is pinned at both ends and must support an axial load P = 25 k. Assume that the wall thickness t is equal to d/20. (Use E = 29,000 ksi and (Y = 36 ksi.)