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 140 900 800- 700 600 500- 400- Critical unit load Sy ks) 120 100 -5,-689 MPa 496 MP Johnson, E 203 GPa, 5, 689 MP 60 " Critical unit load S (MP) 60 Johnson, 300- 40 E-71 GPs. Tangent points Euler, E-203 GP 200- 3,-496 MP Euler, E-71 GPs 20 100 0 20 40 60 80 100 120 140 160 Slenderness ratio p Figure 3