Now we are going to learn how to create bbs of a slab, we have previously learnt the bbs of column, footing and beam. We are going to use all the formulae we learnt in the basics of bbs.
As you can see from the drawing above there are two kinds of bars in this slab. One bar along the main x direction and another one along the y direction. It might seem that we have 4 bars but if you look carefully the black and red bars are actually the same bar but in the opposite direction.
So lets start with the Main X bars
Length of rebar
Slab has a width of 4 m
There is cover of 25mm on each side = 25mm+25mm= 50mm = 0.05m
Effective Slab length = slab width – cover = 4m – 0.05m = 3.95m
Bar Length = Slab length + inclined length
D = Slab Height – cover = 150 – (25 +25) = 100mm
Inclined length = 0.42*D
= 0.42*100= 42mm
Total Length of Main X bar = Effective Slab length + inclined length
= 3.95 + 0.042= 3.992m
Bend Deduction
As we already have learned in the basic of bar bending schedule that for every 45 degree bend we apply a deduction equal to d( 1 times diameter)
Here we have two 45 degree bend so we must apply a deduction of d+d to the total length of the bar
Deduction = 12 +12=24mm = 0.024m
Effective Length = Total Length – Deduction
= 3.992 – 0.024
= 3.968m
Number of bars
No of bars = Distance/spacing + 1
Distance = Slab length – cover = 3.95m
Spacing = 120mm
No of Bars = 3950/120 +1
= 33+1
= 34
Unit Weight
We know that Unit weight of any bar = d2/162
Here out diameter= 12mm
Unit weicht = 12*12/162 = 0.89 kg/m
Total Weight
Total weight = Length*number*Unit Weight
= 3.968 * 33* 0.89
= 116.54 Kg
Main x rebar
Main Y rebar
Length of rebar
Slab has a width of 5 m
There is cover of 25mm on each side = 25mm+25mm= 50mm = 0.05m
Effective Slab length = slab width – cover = 5m – 0.05m = 4.95m
Bar Length = Slab length + inclined length
D = Slab Height – cover = 150 – (25 +25) = 100mm
Inclined length = 0.42*D
= 0.42*100= 42mm
Total Length of Main X bar = Effective Slab length + inclined length
= 3.95 + 0.042= 4.992m
Bend Deduction
As we already have learned in the basic of bar bending schedule that for every 45 degree bend we apply a deduction equal to d( 1 times diameter)
Here we have two 45 degree bend so we must apply a deduction of d+d to the total length of the bar
Deduction = 8 +8=16mm = 0.016m
Effective Length = Total Length – Deduction
= 4.992 – 0.016
= 4.976m
Number of bars
No of bars = Distance/spacing + 1
Distance = Slab length – cover = 4.95m
Spacing = 120mm
No of Bars = 4950/120 +1
= 41+1
= 42
Unit weight
Unit weight of any rebar = d2/162
= 8*8/162
= 0.395 Kg/m
Total Weight
Total weight =Length*number*Unit Weight
= 4.976 * 42* 0.395
= 82.55 Kg
So here is the full bbs of Slab
If you want a free software to make bar bending schedule I highly recommend you download the official BBS app
BBS App Android Google Play Link: Click here to download
iPhone AppStore Line: Click here to download
If you are a fresher civil engineer and want to know how to get a job read this article: How to get a job as a fresher civil engineer.