# Bending stiffness: Definition, Units, Formula, of beam [with Pdf]

Contents

## What is bending stiffness?

Bending stiffness is the resistance offered by the body against bending. It depends on the modulus of elasticity and the area moment of inertia of the object.

As we increase the value of bending stiffness, the strength of an object to resist bending stress also increases.

The bending stiffness of the object can be increased with an increase in the Modulus of elasticity (E) and Moment of inertia (I).

## Bending stiffness equation:

The formula of the Bending stiffness is given by,

Bending stiffness = E × I

Where,
E = Modulus of elasticity
I = Moment of inertia

## Bending stiffness units:

The SI and FPS units of the Bending stiffness are as follows:-

In SI unit:

In the SI system, the unit of modulus of elasticity is N/m² and the unit of moment of inertia is m^{4} therefore unit of bending stiffness is given by,

Bending stiffness = E × I = [\frac{N}{m^{2}}\times m^{4}]=N.m^{2}

Therefore the SI unit of bending stiffness is N.m².

In FPS unit:

In the FPS system, the unit of modulus of elasticity is lb/ ft² while the unit of moment of inertia is ft^{4}. Hence the unit of bending stiffness is given by,

Bending stiffness = E × I = [\frac{lb}{ft^{2}}\times ft^{4}]=lb.ft^{2}

Therefore the FPS unit of bending stiffness is lb.ft².

## Beam bending stiffness:

The bending stiffness of the beam is also known as the flexural rigidity of the beam.

Therefore bending stiffness of the beam at any point is given by the product of modulus of elasticity and moment of inertia about a neutral axis at that point.

Bending stiffness = E × I