Bar bending schedule (BBS) of a continuous beam. (Type-2) / How to calculate the cutting length & weight of rebar's in continuous beam.

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Let us calculate the cutting length & weight of rebars in the RCC continuous beam as shown in the below-given drawing.

The schedule of the beam is given below.

Bottom bar			Top bar			Stirrup
Left	Mid	Right	Left	Mid	Right	Left L/3	Mid L/3	Right L/3
2 -25∅	2-25∅	2-25∅	2-20∅	2-20∅	2-20∅	8mm.	8mm.	8mm.
-------	2 -20∅	-------	2-20∅	-------	2-20∅	100c/c	125c/c	100c/c

 

Given data:

Beam width = 300mm.

Beam depth = 550mm.

Column width = 400mm.

Column length = 480mm.

Effective length L1= 5m = 5000mm.

Effective length L2 = 4.5m. = 4500mm.

Top continuous reinforcement = 20mm ∅ - 2nos.

Top curtail reinforcement (EOS bar) =      20mm ∅ - 2nos.

Bottom continuous reinforcement = 25mm ∅ - 2nos.

Bottom curtail reinforcement     = 20mm ∅ - 2nos.

Stirrup at zone-1 = 8mm∅ @ 100c/c

Stirrup at zone-2 = 8mm∅ @ 125c/c. 

Clear cover = 30mm.

Development length Ld = 50d

Calculation:

A. Cutting length:

a. Bottom bar:

1. Cutting length of the continuous bottom bar

= [L1 + L2+ (2nos. × development length) - (2nos. × 1/2 × column width) - ( 2nos. × 90° bend)]

= [5000mm. + 4500mm. + (2nos. × 50d) - (2nos. × 1/2 × 400mm.)  - ( 2nos. × 2d)]

= [5000mm. + 4500mm. + (2nos. ×50 × 25mm.) - (2nos. × 1/2 × 400mm.)- ( 2nos. × 2× 25mm.)]

= [ 9500mm. +  (2500mm.) - (400mm.)- ( 100mm.)]

= 11,500mm.

= 11.50m. < 12m.

The total length (11.50m.) is less than the available bar length(12m.). Hence there will be no lapping in the bar.

If the total cutting length exceeds 12m., the cutting length should be calculated as given in the below-linked article.

👀. How to calculate rebar cutting length in a beam with lapping?

2. Cutting length of the bottom mid curtail bar-1

= [L1 - {0.1L1 + 0.15L1}]

= [5000mm. - {(0.1× 5000mm. ) + ( 0.15 × 5000mm.)}]

= [5000mm. - {(500mm. ) + (750mm.)}]

= [ 5000mm. - 1250mm ]

= 3750mm.

= 3.75m.

3. Cutting length of the bottom mid curtail bar-2

= [L2 - {0.1L2 + 0.15L2}]

= [4500mm. - {(0.1× 4500mm. ) + ( 0.15 × 4500mm.)}]

= [4500mm. - {(450mm. ) + (675mm.)}]

= [ 4500mm. - 1125mm ]

= 3375mm.

= 3.375m.

b. Top bar:

4. Cutting length of the continuous top bar

= [L1 + L2+ (2nos. × development length) - (2nos. × 1/2 × column width) - ( 2nos. × 90° bend)]

= [5000mm. + 4500mm. + (2nos. × 50d) - (2nos. × 1/2 × 400mm.)  - ( 2nos. × 2d)]

= [5000mm. + 4500mm. + (2nos. ×50 × 20mm.) - (2nos. × 1/2 × 400mm.)- ( 2nos. × 2× 20mm.)]

= [ 9500mm. +  (2000mm.) - (400mm.)- ( 80mm.)]

= 11,020mm.

= 11.02m. < 12m.

5. Cutting length of the top left curtail bar

= [(L1/4) + (development length) - ( 90° bend) ]

= [(5000mm.÷ 4) + (50d) - (2d)]

= [1250mm. + (50 × 20mm.) - ( 2 ×20mm. )]

= [ 1250mm. +1000mm.- 40mm ] 

= 2210mm.

= 2.21m.

6. Cutting length of the top mid curtail bar

= [L1/4 + column width +L2/4]

= [5000/4 + 400mm. + 4500/4]

= [ 1250mm. + 400mm. +1125mm.]

= 2775mm.

= 2.775m.

7. Cutting length of the top right curtail bar

= [(L2/4) + (development length) - ( 90° bend) ]

= [(4500mm.÷ 4) + (50d) - (2d)]

= [1250mm. + (50 × 20mm.) - ( 2 ×20mm. )]

= [ 1125mm. +1000mm.- 40mm ] 

= 2085mm.

= 2.085m.

c. Stirrup:

8. The cutting length of the stirrup bar

= [{2nos. ×  (a +b )} + (2nos.× hook length) -  ( 3nos. × 90° bend) - (2nos. ×135° bend )]

Where,

  a = {beam width - (2 × cover) - (2 × 1/2 × stirrup dia.)} 

     = {300mm. - (2 × 30mm.) - ( 2 × 1/2 × 8mm.)}

     = {300mm. - (60mm.) - (8mm.)}

     = 232mm.

 b = {beam depth - (2 × cover) - (2 × 1/2 × stirrup dia.)} 

     = {550mm. - (2 × 30mm.) - ( 2 × 1/2 × 8mm.)}

     = {550mm. - (60mm.) - (8mm.)}

     = 482mm.

The cutting length of the stirrup

= [{2 nos. × (232mm. + 482mm.)} + (2nos ×10d ) - (3 nos. × 2d ) - (2 nos. × 3d) ]

To know, why we take bend deductions, Go through the article 👇

👀.  What are bend deductions for different angles in reinforcement bars?

Note:  Here, hook length is taken as 10d.

The cutting length of the stirrup

 = [{2 nos. × 714mm.} + (2nos. ×  10 × 8mm) - ( 3 nos. × 2 × 8mm ) - ( 2 nos. × 3 × 8 mm.)]

 = [1428mm. + 160 mm - 48mm - 48mm.]

 = [1588mm. - 96 mm.]

 = 1492 mm i.e. 1.492 m.

B. No. of  stirrups:

For clear span C1:

1. Stirrups in left span:

No. of stirrups

= [{( C1 /3) ÷ stirrup spacing } + 1]

Where,

C1= [(Effective span L1) - (2nos.× 1/2 of column width)]

     = [(5000mm.) - (2 × 1/2 × 400mm.)]

     = 4600mm.

No. of stirrups

     = [{( 4600mm. /3) ÷ 100mm. } + 1]

     = [{1533.33mm. ÷ 100mm. } + 1]

     =   [15.33 +1]

     = 16.33 nos. 

By rounding off = 17 nos.

2. Stirrups in mid-span:

No. of stirrups

     = [{( C1 /3) ÷ stirrup spacing } - 1]

     = [{( 4600mm. /3) ÷ 125mm. } - 1]

     = [{1533.33mm. ÷ 125mm. } - 1]

     =   [12.26 -1]

     = 11.26 nos. 

By rounding off = 11 nos.

3. Stirrups in right span:

Stirrups in right span = stirrups in the left span = 17 nos.

Note:

1. As the spacing is the same, the left & right spans have equal no of stirrups.

2. As we have added 2nos. of stirrups in the left & right span, we have to deduct 1no. from the mid-span.

Total no. of stirrups in span C1

= Stirrups in [left +mid +right]

= [17nos. + 11nos. + 17nos.]

= 45 nos.

For clear span C2:

4. Stirrups in left span:

No. of stirrups

     = [{( C2 /3) ÷ stirrup spacing } + 1]

Where,

C2= [(Effective span L2) - (2nos.× 1/2 of column width)]

     = [(4500mm.) - (2 × 1/2 × 400mm.)]

     = 4100mm.

No. of stirrups

     = [{( 4100mm. /3) ÷ 100mm. } + 1]

     = [{1366.66mm. ÷ 100mm. } + 1]

     =   [13.66 +1]

     = 14.66 nos. 

By rounding off = 15 nos.

2. Stirrups in mid-span:

No. of stirrups

       = [{( C2 /3) ÷ stirrup spacing } - 1]

       = [{( 4100mm. /3) ÷ 125mm. } - 1]

      = [{1366.66mm. ÷ 125mm. } - 1]

      =   [10.93 -1]

      = 9.93 nos. 

By rounding off = 10 nos.

3. Stirrups in right span:

Stirrups in right span = stirrups in the left span = 15 nos.

Total no. of stirrups in span C2

= Stirrups in [left +mid +right]

= [15nos. + 10nos. + 15nos.]

= 40 nos.

The total no. of stirrups in the beam

= Stirrups in [span C1 + span C2] 

= [45 nos. + 40 nos.]

= 85 nos.

Now, let us prepare a BBS table for the RCC continuous beam.

Sl. No.	Type of Bar	Dia. in mm.	Nos.	Length in m.	Total length in m.	Weight in Kg/m.	Total  bar wt. in kg.
1.	Bottom continuous bar	25	2	11.50	23.0	3.854	88.642
2.	Bottom curtail bar-1	20	2	3.75	7.50	2.466	18.495
3.	Bottom curtail bar-2	20	2	3.375	6.75	2.466	16.646
4.	Top continuous bar	20	2	11.02	22.04	2.466	54.35
5.	Top left curtail bar.	20	2	2.21	4.42	2.466	10.899
6.	Top mid curtail bar.	20	2	2.775	5.55	2.466	13.686
7.	Top right  curtail bar.	20	2	2.085	4.17	2.466	10.283
8.	Stirrup bar	8	85	1.492	126.82	0.395	50.094
9.	Total weight of bars =						263.09
10.	Add 3% wastage =						7.89
11.	The grand total wt. of rebar's =						270.98

 

To know, how to calculate the weight of rebars per RMT., Go through the article 👇

❤.  How to calculate the weight of reinforcement bars?

Continued 👉 Part-3👇

👀. Bar bending schedule (BBS) of a simply supported beam. (Type-3)

Thank you for going through these calculation steps❤. Have a good day 😄.

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