# Definition of Shear Force and Bending Moment | What Is Shear Force | What Is Bending Moment | Relation Between Loading, Shear Force & Bending Moment Important Point

## Definition of Shear Force and Bending Moment

### Shear Force Shear force is the unbalanced vertical force which is acting on to the right or left of the section.It’s also termed as aligned forces pushing one part of the body in the specific direction, and the other part of the body is another direction.

Sometimes, a crack is developed in a body from the parallel shear force acting in a different direction at another point of the body. Colinear forces are also termed as compressive forces.

### Bending Moment Bending moment is the algebraic sum of all the moment of forces, according to the right or left of the section. It’s the reaction which is induced in a structural element due to external force or moment is applied.

In the equilibrium position, the moment which is created by external forces is balanced by the couple induced by the internal load; this internal couple is called a bending moment.

## What Is Shear Force : Sign Convention of Shear Force: Shear force is an unbalanced vertical force, so it tends to slide one portion of the beam upward or downward with respect to the other.

Shear force at a section is considered as positive when the left-hand portion tends to slide upward, or the right-hand portion tends to slide downward.

Same as a shear force at a section is negative when the left-hand portion tends to slide downward, or the right-hand portion tends to slide upward.

## What Is Bending Moment : Sign Convention for Bending Moment: We considered bending moment at a section is positive when it tends to bend the beam at a point to a curvature having a concavity at the top or when the moments are acting clockwise direction to the left or anti-clockwise direction to the right.

On the other hand, we considered bending moment at a section is negative when it tends to bend the beam at a point to a curvature having convexity at the top or moments are taken anti-clockwise direction to the left or clockwise direction to the right.

Sometimes the positive bending moment is termed as sagging moment, and the negative bending moment is termed as a hogging moment. The following relations are essential for loading, shear force and bending moment relation-

If there is a point load at a section on the beam, then the shear force suddenly changes(i.e. the shear force line is vertical). But the bending moment remains the same.

If there is no load between two points, then the shear force does not change (I.e. shear force line is horizontal) but the bending moment changes linearly (I.e. bending moment line is an inclined straight line).

If there is a uniformly distributed load between two points, then the shear force changes linearly (I.e. shear line is an inclined straight line). But the bending moment changes according to the parabolic law(i.e. bending moment line will be parabola).

If there us a uniformly varying load between two points then the shear force changes according to the parabolic law(i.e. shear force line will be parabola) but the bending moment changes according to the cubic law.

Where shear force changes, it’s sign there bending moment is maximum.

Where bending moment changes, it’s a sign that point is known as the point of contra flexure or inflation point.

Short Note

### What Is Shear Force and Bending Moment?

Shear and bending moment diagrams are analytical tools used in conjunction with structural analysis to help perform structural design by determining the value of shear force and bending moment at a given point of a structural element such as a beam.

### Definition of Shear Force and Bending Moment

Shear force is taken +ve if it produces a clockwise moment and it is taken -ve when it produces an anticlockwise moment. Bending moment at any point along a loaded beam may be defined as the sum of the moments due to all vertical forces acting on either side of the point on the beam.

### What Is Meant by Shear Force?

Shearing force is defined as the force transverse to the beam at a given section tending to cause it to shear at that section.

### Shear Force

shear force is a force applied perpendicular to a surface, in opposition to an offset force acting in the opposite direction. This results in a shear strain. In simple terms, one part of the surface is pushed in one direction, while another part of the surface is pushed in the opposite direction.

### Bending moment

In solid mechanics, a bending moment is the reaction induced in a structural element when an external force or moment is applied to the element, causing the element to bend. The most common or simplest structural element subjected to bending moments is the beam.

### Shear Force and Bending Moment:

Its baseline is equal to the span of the beam, drawn on a suitable scale. For point loads S.F. diagram has a straight horizontal line, for UDL( Uniformly Distributed Load), It has straight inclined lines, and for uniformly varying loads it has a parabolic curve.

### Shear Forces

Shear force is a force acting in a direction that’s parallel to (over the top of) a surface or cross section of a body, like the pressure of air flow over an airplane wing. The word shear in the term is a reference to the fact that such a force can cut, or shear, through the surface or object under strain.

### What Is Shear Force?

Shear force is the force acting on a substance in a direction perpendicular to the extension of the substance, acting in a direction to a planar cross section of a body. Shear force is also known as shearing force.