In the theory of bending, the assumption that the plane section before bending will remain plane after the bending is made to ensure that:

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HPPSC AE Civil 2016 (HPPTCL) Official Paper

Option 1 : strain is proportional to the distance from the neutral axis

__Explanation:__

Assumption involved in theory of pure bending:

- Material should be isotropic, homogeneous and should follow the hook's law.
- If a plane section before bending remains plane after bending, then the bending strain variation will be linear (
**strain is proportional to the distance from the neutral axis**) with zero at the neutral axis and maximum at the top and bottom fibers. - After bending all the longitudinal planes will bend about a common center of curvature.
- The magnitude of radius of curvature is very large compared to cross-sectional dimensions.
- The Young's modulus assumed to be same in tension as well as compression.