Truss stress compressive/tensile stress

[peet_dk]

Hi

I have found out which truss member that have compressive stress, and which have tensile.
Now I have to select the metal for each member, I know how to find it when it is simple tensile stress (Sigma=Force/Area) But I think there is another equation when it is compressive stress, or?

Do I have to calculate the compressive truss member as a column, and find the critical buckling load?

 

[Rothlisburger]

Yes. The buckling equation for long slender members is Pcr = (pi/L)^2 E I, where Pcr is the critical buckling force, L is the length of the column, E is the modulus of elasticity of the material you're using, and I is the minimum area moment of inertia (second moment of area) for the cross-sectional shape you're using.

-David