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How to Calculate Steel Quantity for Beam, Column and Slab

An important structural element of a building is the slab. There are many different kinds of slabs, but ultimately each one is responsible for moving people from one floor to another in a structure.

A slab can classify as a one way or two-way slab. One-way slabs are divided by main bars running short and distribution bars running long. When the slab length and width are more than 4 meters, two-way slabs typically use, which have bars on both sides.

Proper Calculation the Quantity of Steel for RCC Slab

1. Total Number of Main & Distribution Bar

It's first necessary to determine how many bars you will need for the slabs. It is necessary to determine the number of main bars and distribution bars.

  • The slab's length is 5 meters = 5000 millimeters.
  • The slab has a width of 2 meters = 2000 mm.
  • The slab is 0.150 m thick or 150 mm thick.

Main Bar

  • In a slab with a clear cover, the number of bars equals (Total length of slab - 2 times clear cover)/ centre to centre spacing of the bars plus 1.
  • Total number of bars = (5000- 2 x 25) 100 plus 1.
  • The number of bars is 50.5, which equals 51. The slab requires 51 main bars.

Distribution Bar

  • A distribution bar is equal to (total slab length- 2x clear cover length)/center to center spacing of the bars + 1.
  • The distribution bars should be (2000- 2 x 25) /125 + 1.
  • Bars of distribution equal 16.6 = 17. The distribution bars number 17 in total.

2. Cutting Length of Bar

The slab's clear span is L. Ld is the development length of the bar which is 40 d, where d is its diameter. You can find D by calculating it. A development length is equal to the thickness of the slab minus the clear cover divided by the diameter of the bar.

Calculate the development length by multiplying 150 by 2 x 25 by 12. 88 mm is the development length.

Main Bar

In order to calculate the cutting length of a Main Bar, use the following formula:

  • Length of the main bar to be cut = 2 x Ld + (1 x 0.42 D) ? (2 x 1 d).
  • A bar's main cutting length is 2000 + (2 x 40 x 12) + (1 x 0.42 x 88) - (2 x 1 x 12).
  • The cutting length is 2972.96 millimeters. 2973 mm are the cutting lengths. 2.973 meters is the cutting length.

Distribution Bar

Calculating the distribution bar cutting length:

  • Distribution bar cutting length equals clear span + 2 x Ld.
  • In this example, 5000 plus (2 x 40 x 8) will be the cutting length of the distribution bar.
  • 5640 mm is the length of the distribution bar. 5.4 meters is the length of the cutting bar for distribution bars.

3. Total Weight of RCC Slab

Quantity Calculation of Main bar Steel

  • It requires 51 main bars (as per step 1).
  • Each main bar is 2.973 m long (step 2).
  • Steel Weight = Total Length x Length of 1 m Steel x Diameter of Steel (D2/ 162).
  • Main Bars Total Length = (51 X 2.973).
  • The main bars total 151.623m in length.
  • Main Bar Weight = Total Length x (D2/ 162).
  • The Main Bars weight is 151.623 x (122/162).
  • A main bar's weight is 134.776 kilograms.

Quantity Calculation of Distribution bar Steel

  • It is necessary to have 17 distribution bars (as outlined in step 1).
  • A distribution bar has a length of 5.64 m (as per step 2).
  • Distribution bars total length = (17 x 5.64).

  • 95.88 m is the total length of the distribution bars.
  • Distribution Bar Weight = Total Length x (D2/ 162).
  • 95.88 x (102/162) = 37.87 kg are the weight of the Distribution Bars.

4. Total Steel Weight for RCC Slab

Sum of weights of main bars and distribution bars for steel for a slab equals the total quantity needed for the slab. 133.77 kg plus 37.87 kg is the total amount of steel required for a slab.

A total of 172.646 kg of steel is required for a slab.

To get more details, watch the following video tutorial.

Video Source: We Civil Engineers

How to Calculate Steel Quantity for Beam, Column and Slab