Civil Engineering - Strength of Materials - Discussion

Bending stress is more at top and bottom fibres, so there should be more materials needed. And in circular section less material at top and bottom as compared to rectangular section so it is safe against bending stress and economical too.

Circular section is good in shear as compared to rectangular section because shear stress is more at centre and lower at top and bottom fibre.

Thanks for giving more clarity.

M.I. of the square beam is more than the circular beam, therefore, bending stress is lower in the square for the same cross-section area. You can find the dia of the circular section by equating both areas. Lower the bending stress better than the cross-section.

In rectangular beam, more particles are concentrated on extreme fibre than the circular beam. So they can take up maximum stress occuring at extreme fibres.

Nice explanation, thanks.

Moment of inertia of square beam is more than that of circular beam by keeping same side/diameter. As M.I. increases, square beam is more economical.