Bending Moment - Definition & Calculation at Any Section

Definition

It is the internal resistance to rotation.

OR

Bending moment at a point or at a section is the algebraic sum of Moments caused by forces action to the left or right of that point or section. Mathematically it can be written as

'''Moment = Σ ML = Σ MR'''

Moment can not be find out directly however it can be find out by using many practical and theoretical methods such as:

1. Double integration method
2. Conjugate beam method
3. Area moment method

Bending Moment at any section

Bending moment at any section is the sum of all moments to the left or right of that section.

Positive bending moment

Bending which produces compression in upper (outer) fibers and tension in lower fibers.

Negative bending moment

Bending which produces compression in lower (inner) fibers and tension in upper fibers.