(Solved): 8. An 8m long column is constructed from two 400mmx250mm I-section joists as shown in Figure ...

8. An $8\mathrm{m}$ long column is constructed from two $400\mathrm{mm}\mathrm{x}250\mathrm{mm}$ I-section joists as shown in Figure $\mathrm{Q}8$ below. One end of the column is arranged to be fixed and the other end free. Determine the critical Euler buckling load and the buckling stress. $(1.79\mathrm{MN})$ For each joist: ${\mathrm{I}}_{\max }=213\times 10^{?6}{\mathrm{m}}^4,{\mathrm{I}}_{\min }=9.6\times 10^{?6}{\mathrm{m}}^4,\mathrm{A}=8.4\times 10^{?3}{\mathrm{m}}^2$, with web and flange thicknesses of $20\mathrm{mm}$. For the material of the joist, $\mathrm{E}=208\mathrm{GN}/{\mathrm{m}}^2$.