Important Point

## Introduction of How to Calculate Steel in Rcc Slab

The slab is one of the most important structural elements in the construction of buildings.

Many of us are confused that** how to calculate steel in** **RCC slab**. In this article, we will get to know about the step-by-step procedure to calculate steel in RCC slab.

Slab is a structural member which enables to move from one place is floor to another floor in the structure.

The slabs are basically categorized into two types, **one** **way slab **and **two-way slab**. In one way slab the main bars are provided in the shorter direction and the distribution bars are provided in the longer direction.

In case of the two-way slab the main bars are provided in both directions and two-way slab is generally adopted for the construction when the length and the breadth of the slab are more than 4 meters.

Distribution bar are straight bars and the Main bars are the crank the bars at an angle of **45 degrees** with a **length of 0.42D**

The extra bars are also provided at the bottom of the current bus which is used to maintain the framework of the slab and the** length of the extra bar is L/4**.

## Example of Calculate Steel in Rcc Slab

Let us understand it by taking one example of a one-way slab having **5m length and 2m width**. Take main bars of **12mm diamete**r with a spacing of **100 mm c/c**.

The length of the distribution bars will be 8 mm in diameter and the spacing between the two bars is 125 mm c/c. The overall thickness of the slab is 150 mm with a clear cover of 25 mm on both sides top and bottom.

Also, Read: How to Calculate Slab Steel Quantity from Drawing | BBS of Slab

### Data of Calculate Steel in Rcc Slab-

**Length of the Slab** = 5 m = 5000 mm

**Width of the Slab** = 2 m = 2000 mm

**Thickenss of Slab** = 0.150m = 150 mm

**Step 1. Number of Main Bars & Distribution Bars:**

First upon we have to calculate the number of bars required for the slabs. Here we have to calculate the number of main bars and distribution bars.

**Number of Main Bars**

Formula for calculating a number of bars is as follows.

**Number of Bars = ( Total length of the slab – 2 x clear cover)/ centre to centre spacing of the bars + 1**

**Number of Bars **= (5000- 2 x 25 ) 100 +1

**Number of Bars **= 50.5 = 51 nos

There are **51 nos** of main bars are required for the slab.

**Distribution of Main Bars**

Calculation of number of distribution bars

**Distribution Bars= (Total length of the slab – 2 x clear cover)/center to center spacing of the bars + 1**

**Distribution Bars **= (2000- 2 x 25) /125 +1

**Distribution Bars **= 16.6 = 17 bars

The number of distribution bars are** 17 no**.

### Step 2. Calculate the Cutting Length of Bars:

**Calculate the cutting length of bars**

**For the main bars**

**L**= Clear span of the slab

**Ld **= Development length which is 40 d where d is the diameter of the bar

Calculate the value of D

**Development Length = Thickness of slab – 2 x clear cover – diameters bar**

**Development Length** = 150 – 2 x 25 -12

**Development Length** = 88 mm

**Main Bar Cutting Length **

Formula for calculating the cutting length of **Main Bars** are as follows

**Main Bar Cutting Length **= Length – 2 x Ld + ( 1 x 0.42 D ) – (2 x 1 d)

**Main Bar ****Cutting Length** = 2000 + ( 2 x 40 x 12) + (1 X 0.42 X 88)- ( 2 x 1 x 12)

**Cutting Length** = 2972.96 mm

**Cutting Length **= 2973 mm

**Cutting Length = 2.973 m**

**Distribution Bar Cutting Length **

Calculating the cutting length of distribution bars

**Distribution Bar Cutting Length** = clear span + 2 x Ld

**Distribution Bar Cutting Length** = 5000 + (2 x 40 x 8 )

**Distribution Bar Cutting Length **= 5640 mm

**Distribution Bar Cutting Length** = 5.64 m

### Step 3. Total Weight of Slab Steel :

#### Main Bars Steel Quantity Calculation

The number of main bars required are **51** nos ( as per step 1)

The length of one main bar = **2.973 m** ( as per step 2)

**Weight of Steel = Total Length of Steel x Length of 1 m Steel as per dia of steel (D ^{2}/ 162)**

**Total Length of the Main Bars** = ( 51 X 2.973)

**Total Length of the Main Bars = 151.623m**

**Weight of the Main Bars** = Total Length x ( D^{2}/ 162)

**Weight of the Main Bars** = 151.623 x (12^{2}/162)

**Weight of the Main Bars** = **134.776 kg**** **

#### Distribution Bars Steel Quantity Calculation

The number of distribution bars required are **17** nos ( as per step 1)

The length of one distribution bar =** 5.64 m **( as per step 2)

**Total Length of the Distribution Bars **= ( 17 X 5.64 )

**Total Length of the Distribution Bars **= 95.88 m

**Weight of the Distribution Bars** = Total Length x ( D^{2}/ 162)

**Weight of the Distribution Bars** = 95.88 x (10^{2}/162) = **37.87 kg**

#### Total Weight of Steel

**Total Quantity of Steel Required For Slab = Weight of the Main Bars +Weight of the Distribution Bars**

**Total Quantity of Steel Required For Slab =**** 134.776 kg + 37.87 kg**

**Total Quantity of Steel Required For Slab = 172.646 kg**

### BBS for Slab-

Bar bending schedule or **bbs** plays a significant role in estimating the quantity of steel for beams, columns, and **slab**. It helps to find out bar shape, size, length, weight, bending dimension, etc. In two way **slab**, the **slab** is supported by four sides and loads are carried along with both directions.

### How to Calculate Steel Quantity for Slab:

**Step 1. Number of Main Bars & Distribution Bars.****Step 2. Calculate the Cutting Length of Bars.****Step 3. Total Weight of Slab Steel.**

### Steel Quantity-

This can be done by multiplying cross-section area of steel by its **total length** by density of steel which **7850 kg/m ^{3}**. Total steel quantity of column equal to the sum of both main and stirrup steels.

### Steel Required Per Square Feet-

If we take last thumb rule point, thumb rule for **steel** in RCC structure is **3.5 Kg to 4 kg/ sq.ft. **of built-up area. 3500 Kg to 4000 Kg of **Steel** quantity is **required** for construction of 1000 **square feet** house.

### Reinforcement in Slab-

Structural **reinforcement** is typically placed in the bottom portion of the **slab** thickness to increase the **slab’s** load capacity. Most structural **slabs**-on-ground have both top and bottom layers of **reinforcement** for controlling crack-widths and increasing load capacities.

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