# What is EI in Civil Engineering | What is meant by EI constant in a given structure

What is EI in Civil Engineering | What is meant by EI constant in a given structure... EI is the product of the materials modulas of elasticity (E)...

## What is EI in Civil Engineering

EI is the product of the materials modulas of elasticity (E) and the elements second moment of area (I).

• E is a function of how stiff the material is.
• I is a function of the elements shape.

### What is meant by EI constant in a given structure

The EI value defines how stiff a structure is.

For example in an EI of the simple concrete beam with width b and depth d, the value of I is equal to b*d^3/12.

The deflection can be calculated as 5/384 * w*length^4 / EI.

In this example, the variables are

• The span of the beam (length),
• The weight that the beam carries (w),
• The beam properties (EI).

The EI constant is often an expression in the engineering world to explain the stiffness of a structural element. E is the Modulus of Elasticity, and I is the second moment of inertia.

EI is most often used in FEM (Finite Element Modeling). This expression is a fundamental building block for analyzing complex structures and is a property for many FEM elements (Beams, Bars, Rods, etc.)

Also ReadWhy are I beams shaped like an I?