# Brief Introduction to Reinforced Concrete Design

• What is concrete?
• What is reinforced concrete?
• Strength of concrete.
• Concrete mix ratio for reinforced concrete.
• Types of Steel used for reinforced concrete.
•  letter codes for reinforcement steel.
• Code of practice.
• Structural layout.
• Prior mathematical knowledge.

## What is concrete?

Concrete is produced by the mixture of cement, sand, graded stones and water. It hardens to a solid mass in 28 days.

## What is reinforced concrete?

Reinforced concrete is simply concrete structure that has been strengthened with steel.

## Strength of concrete ( for reinforced concrete)

The strength  is  concrete that  is the accepted standard for reinforced concrete is 24 kN/mm²

## Concrete mix ratio for reinforced concrete

The standard mix ratio for reinforced concrete is 1:2:4. That is, 1 part of cement to 2 parts of fine aggregates (sand) to 4 parts of coarse aggregates ( graded stones/gravel/granite)

## Types of steel used for reinforced concrete.

1. Mild steel: have strength (fy) of  250 N/mm²
2. High yield steel: have strength (fy) of 460 N/mm²

High yield steel is more economical and is mostly used for reinforced concrete design.

## Letter codes for reinforcement steel

R for mild steel

Y for high yield steel  (type 1 bars)

T for high yield steel (type 2 bars)

Square twisted high yield bars are type 1 while ribbed bars are type 2.

## Code of practice

There are many codes of practice for reinforced concrete however the code used in this article is BS 8110.

BS 8110 is the former British code used for reinforced concrete design.

Every country or region has their own design code or uses adopted code from other countries or regions.

## Structural layout

Structural layout is the drawing derived from architectural drawing. It shows  the arrangement of reinforced concrete structural elements such as slabs ,beams and columns and how these elements support the building structure. Structural layout must is done in such a way that it is;

1.Sensible

2.the structural elements are economically arranged.

3. It does not distract or change the original design of the architect except where absolutely necessary and that is after consultation with the architect.

## Prior mathematical knowledge

You should have learnt how to calculate shear forces and moments of framed structures.