How to Calculate Steel in RCC Slab?

How to Calculate Steel in RCC Slab?

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 about 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 an RCC slab.

A slabis 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 bar is provided in the shorter direction, and the distribution bars are provided in the longer direction.

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

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

The extra bar 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.

Also Read: Lumens Vs Luminous Flux

Example of Calculate Steel in Rcc Slab

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 bar of 12mm diameter with a spacing of 100 mm c/c.

The length of the distribution bar will be 8 mm in diameter, and the spacing between the two bar 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 Steel Quantity

Data of Calculate Steel in Rcc Slab-

Data of Calculate Steel in Rcc Slab

  • Length of the Slab = 5 m = 5000 mm
  • Width of the Slab = 2 m = 2000 mm
  • Thickness of Slab = 0.150m = 150 mm

Step 1. Number of Main Bar & Distribution Bar:

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

Number of Main Bar

Formula for calculating a number of bar 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 Bar = (5000- 2 x 25 ) 100 +1
  • Number of Bar = 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 Bar = (2000- 2 x 25) /125 +1
  • Distribution Bar =  16.6 = 17 bar
  • The number of distribution bar are 17 no.

Step 2. Calculate the Cutting Length  of Bar:

Calculate the cutting length  of bar

For the main bar

  • 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 bar 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 (D2/ 162)

  • Total Length of the Main Bar = ( 51 X 2.973)
  • Total Length of the Main Bar = 151.623m
  • Weight of the Main Bar = Total Length x ( D2/ 162)
  • Weight of the Main Bar =  151.623 x (122/162)
  • Weight of the Main Bar = 134.776 kg 

Distribution Bar 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 Bar = 95.88 m
  • Weight of the Distribution Bar = Total Length x ( D2/ 162)
  • Weight of the Distribution Bar = 95.88 x (102/162) = 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

Also, Read: Calculator for Cutting Length of Stirrups | Cutting Length of Rectangular Stirrups | Cutting Length of Square Stirrups | Cutting Length of Circular Stirrups | Cutting Length of Helical Stirrups | Cutting Length of Diamond Stirrups


FAQ

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/m3. 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.

How to Calculate Steel in Rcc Slab?

The Thumb rule to calculate steel in slabs is 3.5 kg to 4 kg/sq. ft of built-up area. On the whole, approximately 3500 kg to 4000 kg of steel is required to build a 1000 square feet structure.

Steel Required for Slab

The Thumb rule to calculate steel in slabs is 3.5 kg to 4 kg/sq. ft of built-up area. On the whole, approximately 3500 kg to 4000 kg of steel is required to build a 1000 square feet structure. This is one of the most basic important information that one must be aware of before building his/her own dream house.

Rcc Slab Steel Calculator

Determine the dimensions of the slab (Length, Width, and Thickness).
Let’s assume the dimensions of the slab are:

Length = 6 meters
Width = 4 meters
Thickness = 0.15 meters

Steel Calculator for Slab

Determine the steel reinforcement required for the slab.

The amount of steel reinforcement required for a slab is usually expressed as a percentage of the total cross-sectional area of the slab. The percentage varies depending on the type of slab and the loads it will be subjected to. For a general-purpose RCC slab, we can assume a steel percentage of 1%.

Area of the slab = Length x Width = 6 x 4 = 24 square meters

Steel reinforcement required = 1% of the area of the slab = 1/100 x 24 = 0.24 square meters

Roof Slab Steel Calculation

Calculate the volume of the slab.

  • Volume = Length x Width x Thickness
  • Volume = 8 x 6 x 0.15
  • Volume = 7.2 cubic meters

Area of Steel Formula in Rcc

As per thumb rule steel quantity required in the formation of RCC beam should be 2% of total volume of concrete. To calculate the steel quantity in beam as 2% of volume of concrete = 0.02 x 7850 x 5.29 = 830 kg.

Slab Steel Calculation

The total steel quantity per slab must be equal to the total amount of main steel and stirrup steels. In simple terms, one can just multiply the length of the slab by its width and then divide the area by 12.5.

Roof Rod Calculation

Calculate the total surface area of the roof slab in square meters.
The surface area of the roof slab can be calculated as follows:
Total surface area = Length x Width
Total surface area = 10 x 8
Total surface area = 80 square meters

Tmt Bar Calculation for Roofing

The area of each TMT bar can be calculated as follows:
Area of each bar = (pi x diameter^2)/4
Let’s assume we are using 12mm diameter TMT bars.
Area of each bar = (3.14 x 12^2)/4
Area of each bar = 113.1 square millimeters

Steel Calculation for Slab Online

  1. Open your preferred search engine and search for “Online Steel Calculation for Slab” or similar keywords.
  2. From the search results, select a reliable and trustworthy website that offers a steel calculation tool for slabs.
  3. Once you are on the website, enter the required details of the slab such as length, width, thickness, and spacing between the steel bars or rods.
  4. The online steel calculation tool will then automatically calculate the amount of steel required for the slab and display the results on the screen.

Slab Size in Mm

In a residential building it is 9 ʺ × 12 ʺ or 225 mm × 300 mm standard size according to (IS codes). The minimum RCC beam size should not be less than 9 ʺ × 9 ʺ or 225mm × 225mm with the addition of a 125mm slab thickness. The size of the columns depends on the total load on the columns.

Rcc Slab Calculation Formula

To calculate the amount of concrete required for an RCC (Reinforced Cement Concrete) slab, you can use the following formula:

Volume of concrete = Length x Width x Thickness

Where:

  • Length is the length of the slab in meters
  • Width is the width of the slab in meters
  • Thickness is the thickness of the slab in meters

Steel Required for Slab Per Square Feet

The amount of steel required for an RCC (Reinforced Cement Concrete) slab per square feet depends on several factors such as the design, thickness, and the spacing of the steel bars. As a general rule of thumb, the amount of steel required for an RCC slab is typically between 0.5% to 2% of the total volume of concrete.

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