Introduction of How to Calculate Steel in Rcc Slab
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.
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 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.
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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.
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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
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