#### Design of RCC Structures | Basic definitions and formulas

**In this article, we will go through the basic definitions of Stress, strain, elastic materials and modulus of elasticity. This will be our first step towards understanding the design of “Singly reinforced sections”.**

#### What is stress and how does it develop?

When an object is subjected to an external force, the object tends to build up internal resistance within itself (material). This resistance is termed as “stress”.

In short, stress can be defined as load per unit area.

**Stress can be classified into four types:**

- Compressive stress
- Tensile stress
- Bending stress
- Shear stress

Stress = Load/Area = W/A = N/mm2

Where, N = Newton

#### What is Strain?

To make it easier for you to understand, let’s merge the definition of stress with strain.

When an object is subjected to an external load, the internal resistance which is built up with the object itself is not enough to withstand the external load results into deformation of the object. This alteration or deformation of the object is called strain.