HOW TO CALCULATE STEEL QUANTITY FOR SLAB WITH BAR BENDING SCHEDULE
Hi before going to calculate bar bending schedule for slab you should know to find your slab is whether oneway slabÂ orÂ twoway slab.Â If not itsÂ okÂ we will guide through this
One Way Slab  Ly/Lx > 2 
Two Way Slab  Ly/Lx < 2 
In oneway slab,Â Main bars are provided in shorter direction (Cranked bars) and distribution bars are provided in Longer direction (Straight bars).
in Twoway slabÂ Main bars (cranked bars) are provided in both directions.
Distribution bars:Â These bars are straight bars.
Main bars:Â These bars are cranked bars. Main bars are cranked at an angle of 45 Degree with the length of 0.42D
therefore,
D = Depth of Slab – Top cover â€“ Bottom cover
Extra Bars:Â The extra bar is provided at the bottom of Cranked bars to maintain the framework of the slab. The length of Extra bar is L/4
OKÂ We Think You Got A Clear Picture Of Slab ReinforcementsÂ Now Take Look Of This DetailingÂ
Let We Work On This Detailing So You Can Get Clear Picture
GIVEN DATA FOR FLOOR SLAB 1
SIZE OF FLOOR SLAB 1
Length= 2950mm
Breadth= 6000mm
Beam size = 225x300mm
Main bars are 12 mm in diameter @ 150 mm centre to centre spacing
Distribution bars are 8 mm in diameter @ 150 mm centre to centre spacing. (Main Bar & Distribution Bar Difference)
Top and Bottom Clear Cover is 25 mm
Thickness of Slab â€“ 150 mm
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Therefore, To Find ItsÂ One WayÂ OrÂ Two Way Slab
Lx = 2950mm (shorter span)
Ly = 6000mm (Larger span)
Ly/Lx= 6000/2950 = 2.033
One Way Slab  Ly/Lx > 2 
Hence itsÂ onewayÂ slab
So, We need to find
 Main barÂ for shorter span
 Distribution barÂ for longer span
 Top barÂ for main rod on both sides for critical structure
LCETEDÂ TRIVIA
 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
STEP 1
Find Cutting Length OfÂ Main BarsÂ ForÂ Floor Slab 1
Length Of Main BarsÂ = (depth of beam/2) + (width of beam/2) +Â (1 x inclined length) â€“ (45Â° bend x 2)Â Â +Â length ofÂ Â shorter spanÂ + width of beam + (0.3 x intermediate slab length)
Inclined length = 0.42D
D = Slab thickness â€“ 2 side clear cover (top cover + bottom cover)
D = 150 â€“ (2 x 25) = 100mm
Inclined length = 0.42 x 100 = 42mm
45Â° bend = 1d
d = diameter of bar
45Â° bend = 1 x 12 = 12mm
Intermediate slab
L = 3100mm
Therefore,
Length Of Main BarsÂ = (300/2) + (225/2) + (1 x 42) – (12 x 2)Â Â + 2950 + 300 + (0.3 x 3100) =Â 4730.5
Cutting length Of Main Bars forÂ floor slab 1= 4.8m
STEP 2Â
No Of Bars Required For Cutting Main Bars
No of bars = (opp length/spacing) + 1
Opposite length of bar = 6000
Spacing = 150mm c/c as per given details
= (6000/150) + 1
No of bars = 41 nos
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STEP 3
Total Length Of Bar Required ForÂ Main BarsÂ OfÂ Floor Slab 1
= no of bar x total length of bar
= 41 x 4.80 = 196.8m = 197m
Total length of bar required for main bars of
Floor Slab 1 =197m of 12mm rod
STEP 4
Find Cutting Length Of Distribution Bars ForÂ Floor Slab 1
Length of distribution bars =Â (breadth of beam/2) + length of longer span + (breadth of beam/2)
Length of distribution bars = (225/2) + 6000 +(225/2) = 6225mm
Length of distribution bars = 6.225m
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Estimate this Slab (Drawing Included)
STEP 5
No Of Bars Required For Cutting Distribution Bars
No of bars = (opp length/spacing) + 1
Opposite length of bar = 2950
Spacing = 150mm c/c as per given details
= (2950/150) + 1
= 20.6666666667 = 21 nos
No of bars = 21nos
STEP 6
Total Length Of Bar Required ForÂ Distribution BarsÂ OfÂ Floor Slab 1
= No Of Bar X Total Length Of Bar
= 21 x 6.225 = 130.725m
Total length of bar required for distribution bars ofÂ Floor Slab 1 = 131m of 8mm rod
STEP 7
Top Bar (Extra):Â Top Bars Are Provided At The Top Of Main Bar As Critical Length (L/4) Area
Number of top bars = (Lx/4) / spacing + 1
Number of top bars = ((2950/4) / 150) + 1 =5.91 = 6 nos of bars x 2 sides =Â 12 nos
Number of top bars = 12 nos of bars
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STEPÂ 8
Total Length Of Bar Required ForÂ Top BarsÂ OfÂ Floor Slab 1
Length of top bars = Length of Distribution Bars
Cutting Length Of top Bars =Â 6.225m
Total length of top bars =Â 6.225Â x 10 = 27.25m
Total length of top bars ofÂ Floor Slab 1= 63 m of 8mm rod
GIVEN DATA FOR FLOOR SLAB 2
SIZE OF FLOOR SLAB 1
Length= 3100mm
Breadth= 6000mm
Therefore,
Lx shorter span = 3100mm
Ly larger span = 6000mm
Beam size = 225x300mm
Main bars are 12 mm in diameter @ 150 mm centre to centre spacing
Distribution bars are 8 mm in diameter @ 150 mm centre to centre spacing. (Main Bar & Distribution Bar Difference)
Top and Bottom Clear Cover is 25 mm
Consider Development length as 40 d
Thickness of Slab â€“ 150 mm
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Therefore, To Find ItsÂ One WayÂ OrÂ Two Way Slab
Lx = 3100mm (shorter span)
Ly = 6000mm (Larger span)
Ly/Lx= 6000/3100 = 1.93
Two Way Slab 
Ly/Lx < 2 
Hence itsÂ TwowayÂ slab
So, We need to find
 Main barÂ for shorter span
 Main barÂ for longer span
 Top barÂ for main rod on both sides for critical structure
STEP 1
Find Cutting Length OfÂ Main BarsÂ ForÂ Floor Slab 2Â (A2B2 direction)
Length Of Main BarsÂ (A2B2)Â = (depth of beam/2) + (width of beam/2) +Â (1 x inclined length) â€“ (45Â° bend x 2)Â Â + length of span + width of beam + (0.3 x intermediate slab length)
Inclined length = 0.42D
D = Slab thickness â€“ 2 side clear cover (top cover + bottom cover)
D = 150 â€“ (2 x 25) = 100mm
Inclined length = 0.42 x 100 = 42mm
45Â° bend = 1d
d = diameter of bar
45Â° bend = 1 x 12 = 12mm
Intermediate slab
L = 3000mm
Therefore,
Length Of Main BarsÂ (A2B2)Â = (300/2) + (225/2) + (1 x 42) – (12 x 2)Â Â + 3100 + 300 + (0.3 x 3000) = 4580.5
Cutting length Of Main Bars forÂ floor slab 2= 4.6m
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STEP 2Â
No Of Bars Required For Cutting Main Bars
No of bars = (opp length/spacing) + 1
Opposite length of bar = 6000
Spacing = 150mm c/c as per given details
= (6000/150) + 1
No of bars = 41 nos
STEP 3
Total Length Of Bar Required ForÂ Main BarsÂ OfÂ Floor Slab 2
= no of bar x total length of bar
= 41 x 4.6= 188.6m = 190m
Total length of bar required for main bars of
Floor Slab 2Â =190m of 12mm rod
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STEP 4
Find Cutting Length OfÂ Main BarsÂ ForÂ Floor Slab 2Â (C2D2 direction)
Length Of Main BarsÂ (C2D2)Â = (depth of beam/2) + (width of beam/2) +Â (1 x inclined length) â€“ (45Â° bend x 2) + length of span + (width of beam/2)
Inclined length = 0.42D
D = Slab thickness â€“ 2 side clear cover (top cover + bottom cover)
D = 150 â€“ (2 x 25) = 100mm
Inclined length = 0.42 x 100 = 42mm
45Â° bend = 1d
d = diameter of bar
45Â° bend = 1 x 12 = 12mm
Intermediate slab
L = 3000mm
Therefore,
Length Of Main BarsÂ (C2D2)Â = (300/2) + (225/2) + (1 x 42) – (12 x 2)Â Â + 6000 + (225/2) = 6393m
Cutting length Of Main Bars forÂ floor slab 2= 6.4m
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STEP 5 eÂ
No Of Bars Required For Cutting Main Bars
No of bars = (opp length/spacing) + 1
Opposite length of bar = 3100
Spacing = 150mm c/c as per given details
= (3100/150) + 1
No of bars = 21.6666666667 = 22
STEP 6
Total Length Of Bar Required ForÂ Main BarsÂ OfÂ Floor Slab 2
= no of bar x total length of bar
= 22 x 6.4= 140.8m = 141m
Total Length Of Bar Required For Main Bars Of
Floor Slab 2Â =141m Of 12mm Rod
STEP 7
Top Bar (Extra)Â (A2B2): Top Bars Are Provided At The Top Of Main Bar As Critical Length (L/4) Area
Number of top bars = (Ly/4) / spacing + 1
Number of top bars = ((6000/4) / 150) + 1 = 11 nos of bars x 2 sides = 22 nos
Number of top bars = 22 nos of bars
Top Bar (Extra)Â (C2D2): Top Bars Are Provided At The Top Of Main Bar As Critical Length (L/4) Area
Number of top bars = (Lx/4) / spacing + 1
Number of top bars = ((3100/4) / 150) + 1 =6.16 = 7 nos of bars x 2 sides = 14 nos
Number of top bars = 14 nos of bars
STEPÂ 8
Total Length OfÂ Bar Required ForÂ Top BarsÂ OfÂ Floor Slab 2Â (A2B2)
Length of top bars = Length of Opposite BarsÂ (C2D2)
Cutting Length Of top Bars =Â 3.325m
Total length of top bars =Â 3.325Â x 14 = 46.55m
Total length of top bars ofÂ Floor Slab 2= 47 m of 8mm rod
Total Length Of Bar Required ForÂ Top BarsÂ OfÂ Floor Slab 2Â (C2D2)
Length of top bars = Length of Opposite BarsÂ (A2B2)
Cutting Length Of top Bars =Â 6.225m
Total length of top bars =Â 6.225Â x 14 = 87.15m
Total length of top bars ofÂ Floor Slab 1= 88m of 8mm rod
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RESULT,
FLOOR SLAB 1,
Main Bars = 185m Of 12mm Rod
Distribution Bars = 131m Of 8mm Rod
Top Bars = 63m Of 8mm Rod
FLOOR SLAB 2,
Main Bars = 190m of 12mm rod
Main Bars = 141m Of 12mm Rod
Top Bars = 88 m of 8mm rodÂ (A2B2)
Top Bars = 47m of 8mm rodÂ (C2D2)
TOTAL
12mm rod required = 516m
8mm rod required =Â 329m
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