# Difference Between Main Bars And Distribution Bars

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• 0:0 min

• 26 Aug 2024

In any reinforcement detailing there are two sizes of bars used in the slab. That is main reinforcement bars and distribution bars. In this article, we will discuss the difference between main bar and distribution bar.

To understand properly we need to know the bending moment on slab.

Let’s take an example.

When load is applied to a slab the bottom of the slab will experience positive moment (Sagging) and the supports will experience negative moments (Hogging). The bottom part, as well as the top part of the slab, will experience high tension at the same time.

The deflection will be very high in shorter span and low in longer span. High amount of tension will be acting in the support which is near than the other one.

## Function Of Main Reinforcement Bars:

Main reinforcement bar is provided at the shorter span direction in order to transfer the bending moment developed at the bottom of the slab. The purpose of providing main bar is to transfer the bending load developed at the bottom of the slab to the beams.

1. Main reinforcement bar is provided at the bottom of the slab at the shorter direction.

2. Stronger dimension bar is used as main bar.

In one way slab, the slab is supported by beams on the two opposite sides where main reinforcement bar is provided.

In two way slab, the slab is supported by beams on all four sides. So there will be no difference in bar size because each side will have to transfer equal amount of stress evenly.

### Function Of Distribution Bars:

• Distribution bars are provided to resist the shear stress, cracks developed in the longer span.
• Distribution bars are provided perpendicularly with the top of the main bar.
• Lesser dimension bars are used.
• Distribution bars are provided in the longer span direction.

### Difference Between Main Bars And Distribution  Bars:

• Main reinforcement bar is normally used at the bottom of the slab.

Distribution bars are placed on the top of the main bar.

• Main bar is used in shorter direction but distribution bar is used in longer span.
• Higher dimension bar is used as main reinforcement bar.

Lower dimension bar is used as distribution bars.

• Main reinforcement bar is used to transfer the bending moment to beams.

Distribution bars are used to resist the shear stress, and cracks developed at the top of the slab.

## FAQ

### What is the difference between main steel and distribution steel in slab?

Main steel reinforcement is the one place along shorter direction and the distribution steel is place along longer side. Moreover, they both vary in many situations, like design in which the main steel was provided with more stress and distribution was provided with less strength

### What is the difference between main bar and secondary bar?

Here is the difference between them. Main Reinforcement – They are used to take the bending moment produced in the slabs. Distributive(Secondary) Reinforcement – They are provided to support the main bars and to hold the main bars in their position

### How to calculate main bars and distribution bar?

Where, d = diameter of bar. = 2838 mm = 2.838 m. Weight of main bars = [d2×L162]×34=[122×2.838162]×34 = 86 kg. Weight of distribution bars = [d2×L162]×14=[82×5.64162]×14 = 31 kg

### What is the main bar of a column?

The main bar’s length runs parallel to the floor’s height. The length of the main bar is calculated by adding the height of the column, the height of the top slab and the overlap length, which is added to the top end of the column for the next floor. Length of each main bar= Floor Height + Slab Height + Overlap Length

### Why distribution steel is provided above the main steel?

Distribution steel in slabs is provided for the following reasons: To prevent formation of cracks due to shrinkage and temperature stresses. To hold the main bars

### What are the main steel bars in a slab?

Main bars are always placed at the bottom part of the slab reinforcement and distribution bars rest over the main bar as shown in the above drawing. The diameter of the main bar should not be less than 8mm for the HYSD bar and 10mm for plain bars

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