For the same cross-sectional area, which column provides the higher buckling load: a circular bar or a circular tube?

Circular tube

Explanation:

Now for better understanding lets take an example

Lets take

Diameter of solid bar= cm

Outer diameter of tube =6 cm

Inner diameter of tube=2 cm

So from we can say that both tubes have equal cross sectional area.

We know that buckling load is given as      

If area moment of inertia(I) is high then buckling load will be high.

We know that  area moment of inertia(I)

For circular tube

For circular bar  

Now by putting the values

    For circular tube

  For circular bar

So we can say that for same cross sectional area the  area moment of inertia(I) is high for tube as compare to bar.So buckling load  will be higher in tube as compare to bar.