Question

Consider a simply supported beam with a uniformly distributed load having a neutral axis (NA) as shown. For points P(on the neutral axis) and Q (at the bottom of the beam) the state of stress is best represented by which of the following pairs?

• A.
• B.
• C.
• D.

Answer 1

The correct option is B

In a simply supported beam two types of stress acts


1. Flexural stress

$\sigma =\frac{MY}{l}$ &

2. Shear stress

$\tau =\frac{VA\overline{Y}}{I_b}$

All the symbols have their usual meaning
Point P
$\therefore$ Point P lies on NA
$\therefore y=0$
$Hence,\sigma =0$
Point P also lies at mid span, So shear force,
V = 0
Hence, $\tau =0$
Point Q
At point Q flexural stress is acting and nature of which is tensile due to downward loading.
As the point Q lies on bottom of beam


So V = 0
$Hence,\tau =0$
Hence, state of stress should be as shown.