3. Specify the diameter of a round column 1.5 m long that is to carry a maximum load estimated to be 22 kN. Use a design factor na=4 and consider the ends as pinned (rounded). The column material selected has a minimum yield strength of 500 MPa and a modulus of elasticity of 207 GPa. 180 1200 1100- 160 1000- 140 900- 120 100 50 S, 496 MPa 80 B Critical unit load Sc (MPa) 880 700 600 500 400- 800- Critical unit load Scr (ksi) 60 S₁ = 689 MPa Johnson, E=203 GPa, S, = 689 MPa 300- 40 10 200- Johnson, E = 71 GPa, 5, 496 MPa Tangent points Euler, E 203 GPa Euler, E 71 GPa 20 100- 0 0 20 40 60 80 100 120 140 160 Slenderness ratio Lelp Figure 3