Bar bending schedule of 2 way slab

Bar bending schedule of two way slab and How to calculate the cutting length and weight of rebar’s in 2 way slab?

In this Article we will calculate the cutting length and  prepare the B.B.S of the 2 way slab as shown below.

Let us redraw the above drawing with the dimensions for the calculation purpose as below.

Given Data.

Dimension of  slab

Lx = five m.= 5000-mm.

Ly = three m. = 3000-mm.

Thickness = 125-mm.

Main bar-One = 10mm@ 150 c/c

Main bar-Two or say distribution bar) = 10-mm @ 150 c/c

Top extra bar-One = 8-mm @ 150 c/c

Top extra bar Two  8-mm @ 150 c/c

Clear cover of the slab = 25-mm.

Development length Ld = 45-d.

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Calculation steps.

1  -The no. of the bars

a –  Main bars.

The no. of main bars – One

= [Lx ÷ bar spacing ] + One

= [ 5000 ÷ 150] + One

= 33.33 + One

= 43.33 nos.

By rounding off = 44 nos.

 b – Main bars – 2.

The no. of the main bars – Two ( or say distribution bar)

= [Ly ÷ bar spacing ] + One

= [ 3000 ÷ 150] + One

= 20 + One

= 21 nos. 

c – Top extra bars- One.

The no. of the top extra bars-One on one side

= [{(Ly ÷ Fore)÷ bar spacing} + One]

= [{ (3000 ÷ Fore) ÷ 150} +One]

= [{ 750 ÷ 150} +One]

= [{ 5} +One]

= Six nos.

The total no. of the top extra bars on both sides.

= [2 sides × Six nos.]

= 12 nos. 

Note: The top extra bars are provided at the Ly/fore span of the main bar on the both sides.

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c – Top extra bars- Two .

The no. of the top extra bars- Two on one side

= [{(Lx ÷ 4)÷ bar spacing} +One]

= [{ (5000 ÷ 4) ÷ 150} +One]

= [{ 1250 ÷ 150} +One]

= [{ 8.33} +One]

= 9.33 nos.

By rounding off = Ten nos.

The total no. of the top extra bars on both sides

= [Two sides × 10nos.]

= 20 nos. 

Note: The top extra bars are provided at the Lx/fore span of the main bar on the both sides.

2 – Cutting length.

a – Main bar- One.

 

Cutting length of the main bar- One

Here, D = [slab thickness – ( top and bottom clear cover) + bar diameter ]

= [125mm – (Two nos × 25 mm.) +Ten mm ]

=  [125mm – 60 mm]

D = 65 mm.

Cutting length of the main bar- One.

= [ 3000mm. + ( Two nos. × 45 × Ten mm. ) + ( 0.42× 65mm. ) – ( Two nos. × One × 10mm)]

= [ 3000mm. + 900mm. + 27.3mm. – 20mm. ]

= 3907.30 mm. = 3.91m.

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b – Main bar- Two.

Cutting length of the main bar – Two

c – Top extra bar – One.

Cutting length of the top extra bar- One

= [clear span Lx + (Two nos. × development length)]

= [5000mm. + ( Two nos. × 45d )]

=  [ 5000mm. + ( Two nos. × 45 × 8mm. )]

= [ 5000mm. + 720mm.]

= 5720 mm. = 5.72m.

d – Top extra bar- Two.

Cutting length of the top extra bar- Two

= [clear span Ly + (Two nos. × development length)]

= [3000mm. + ( Two nos. × 45d )]

=  [ 3000mm. + ( Two nos. × 45 × 8mm. )]

= [ 3000mm. + 720mm.]

= 3720 mm. = 3.72m.

Let us prepare the B.B.S table to calculate the weight of rebars.

Sl. No.	Type of Bar	Dia. in mm.	Nos.	Length in m.	Total length in m.	Weight Kg/m.	Total  bar wt. in kg.
1.	Main bar- One	10	44	3.91	172.04	0.617	106.15
2.	Main bar- Two	10	21	5.91	124.11	0.617	76.58
3.	Top extra bar- One	8	12	5.72	68.64	0.395	27.11
4.	Top extra bar-Two	8	20	3.72	74.40	0.395	29.39
4.	Total weight of the bars =						239.23
5.	Add three % wastage =						7.18
6.	The grand total wt. of the rebar’s =						246.41

 

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1. Brick Size and standard Brick dimensions 

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3. BBS For RCC Column

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