What is bending ? How bending problems prevents and what is buckling ?

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A bridge has to be designed such that it can withstand the load of the flowing traffic, the force of winds and its own weight. Means it should not bend too much or break.

Similarly, in the design of building use of beams and column is very common.

In both the cases, the overcoming of the problem of bending of beam under a load is important.

Let us consider the case of a beam loaded at the centre and supported near its ends as shown in figure $(a)$.

A bar of length $l$, breadth $b$ and depth $d$ when loaded at the centre by a load $\mathrm{W}$ sags by an amount given by,

$\delta=\frac{\mathrm{W} l^{3}}{4 b d^{3} \mathrm{Y}}$

where $\mathrm{Y}=$ Young modulus

This equation shows that,

Bending $\delta \propto \frac{l^{3}}{b d^{3} \mathrm{Y}}$

Means for reduce the bending for the given load, the distance between two support must be small or one should use a material of beam with large Young's modulus.

890-s68

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