The bars of the truss have the cross section shown. The outer radius of the hollow circular cross section is R = 15 mm. The bars consist of material with modulus of elasticity E = 70 GPa. If the force...

The bars of the truss have the cross section shown. The outer radius of the hollow circular cross section is
R
= 15 mm. The bars consist of material with modulus of elasticity
E
= 70 GPa. If the force
F
is gradually increased, at what value will the structure fail due to buckling?