Bar Bending Schedule – (BBS) Basic Formulas

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Bar Bending Schedule – (BBS) Basic Formulas

 

Bar bending Schedule is the process of cutting & Bending of reinforcement bar in to the required shape.

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 Importance of Bar Bending Schedule?

 

a). Location & Marking of Bar.

 

b). Type of Bar.

 

c). Size of Bar.

 

d). Cutting Length of the bar.

 

e). The number of Bar.

 

f). Bending details of Bar

 

g). Total quantity.

 

Advantages of Bar Bending Schedule?

 

1). Cutting length & bending of reinforcement can be done by Bar Bending Schedule.

 

2). B.B.S avoids wastage of reinforcement& thus saves the project cost.

 

3). It provides a better estimation of reinforcement steel requirements for each & every structure member.

 

4). B.B.S is very much useful during auditing of reinforcement & provides check or theft & pilferage.

 

5). It enables easy & fast preparation of bills of construction work for clients & contractors.

 

Why Steel is used As Reinforcement Bar?

 

i). Coefficient of thermal expansion characteristics similar to concrete.

ii). Good strength for the economic design of R.C.C structure.

 

iii). Good gripping or good bonding with concrete.

 

iv). Good resistance against corrosion for higher durability.

 

v). Good bed ability for providing required shape.

 

Standard Length of Bar -12meter or 40 feet.

 

Size & Unit Weight of Bars

 

Dia. Of Bar Unit Weight of Bar (D2/162)
8mm (8×8)/162 = 0.395 kg/m.
10mm (10×10)/162 = 0.617 kg/m.
12mm (12×12)/162 = 0.889 kg/m.
16mm (16 x16)/162 = 1.580 kg/m.
20mm (20×20)/162 = 2.470 kg/m.
25mm (25×25)/162 = 3.858 kg/m.
32mm (32×32)/162 = 6.320 kg/m.

 

Bend Deduction of bars & values

 

Bend increases the length of bars. So we need a lesser length than we see in the drawing. So, Cutting length is taken lesser than the required length.

 

For 45 degree Bend

 

Bar Bending Schedule

 

Always take – 1d

 

For 90 Degree Bend

 

Bar Bending Schedule

 

Always take – 2d

 

For 135 Degree Bend

Bar Bending Schedule

 

Always take – 3d

 

For 180 Degree Bend

 

Bar Bending Schedule

Always take – 4d

 

Clear Cover & Effective Cover

 

 

The cover is the thickness of concrete measured from the nearest outer surface of reinforcement. The cover is mainly provided to protect the reinforcement bars. In RCC structure reinforcement provided in concrete up to a specific distance from the face of the member. 

 

Clear Cover

 

The clear cover is the distance between the outer surface of the concrete to the nearest surface of the reinforcing bar.

 

 

 

Effective Cover

 

The effective cover is the distance measured from the face of the member to the center of the area(centroid) of the main reinforcement. This is the dimension mostly used for design calculation.

 

Effective cover = Clear cover + Dia of stirrups/ links + 0.5 x Dia of main reinforcement bar.

 

 

 

Values of Clear Cover

 

FOOTING 50mm
COLUMN 40mm
BEAM 25mm
SLAB 20mm
STAIRCASE 15mm
CHAJJA 15mm
PILE 60mm
PILE CAP 60mm

 

Standard Codes Used For BBS

 

IS Code: 456-2000 Plain & Reinforced Concrete

 

1S Code 2502-1963 Code of Practice for bending & fixing.

 

IS: 5525-1969 Detailing of reinforcement in RCC work.

 

SP 34-1987 Concrete Reinforcement Detailing.]

 

Symbols & Representation in BBS

 

Symbols Representation
ϴ Plain Round Bar
Plain Square Bar
# Deformed Bar
@ Center to center spacing

 

Cutting Length of Bars

 

Shape of Bar Cutting Length of Bar

CL – a + L + b – bend deduction

Bend deduction – 2 x 2d (90*).

CL – a + L – bend deduction

Bend deduction – 1 x 2d (90*).

CL – L + (2 x Hook Length)

 Hook Length = 10D

 

 

Cutting Length of Crank Bar

 

 

Crank length – 0.42d.

 

 Cutting Length – Ld + Span Length (L) + { 0.42H x 2} + Ld – Bend Deduction (2 x 90* + 4 x 45*).

 

 

Hook

 

 

 

Length of hook = 9d or 10d, (where d is the diameter of the bar)

 

Length of bar = L + 9d + 9d meter

 

Cutting Length Of Rectangular Stirrups

 

Bar Bending Schedule
Bar Bending Schedule

 

Cutting Length Of Rectangular Stirrups – (a x 2) + (b x 2) + Hook Length

 

Where, a  =  A – (2 x clear cover) – d

 

a =  B – (2 x clear cover) – d

 

Hook Length = 2 x 10D

 

Cutting Length Of Triangular Stirrups

 

 

Bar Bending Schedule

 

Cutting Length Of triangular Stirrups – (H x 2) + a + Hook Length

 

Where, H  =  (x2 + y2)⅟2  Where,  X = a/2 & Y = b

 

a =  A – (2 x clear cover) – d

 

b =  B – (2 x clear cover) – d

 

Cutting Length Of Circular Stirrups

 

Bar Bending Schedule

 

 

Cutting Length of Circular Stirrups = (Pi x d) + Hook length

 

Where d = D – (2 x clear cover) – Dia of the bar.

 

Cutting Length of Diamond Stirrups

 

Bar Bending Schedule

 

 

Cutting length of diamond stirrups = (H x 4) + Hook Length

 

Where, H = (x2 + y2)

 

Where, x = a/2 & y = b/2.

 

Cutting Length of Spiral or Helix Stirrup

 

Bar Bending Schedule

 

 

Length of Helix/Spiral Bar = n√ c2 + p2

 

So, first, we should find out the value of ‘n’ & ‘c’.

 

No. of Pitches (n) = H/p+1

 

Where, Length of pile cage  = H

 

 

Pitch or spacing of spiral = P

 

Circumstances (C) = x d

 

Where,

 

Dia of spiral Ring (d) = D – (2 x cc) – Dia of the bar.

 

Cutting Length of Chair bar

 

Bar Bending Schedule
Bar Bending Schedule

 

 

Cutting length of chair bar = 2A + 2D + B

 

Where, A = (2 x spacing) + 50

 

B = 50d

 

D = Footing height – [{ upper + lower cc} + ( Upper side main + dist bar dia + lower side main bar dia)]

 

I hope this information can be useful for you guys,

 

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Thanks For the Great Attention!

 

Good Bye & Take Care

 

Happy Learning 

 

 

Also, Read

 

Calculate Footing Bar Bending Schedule (BBS) & Steel Quantity in Footing

Bar Bending Schedule of Beam and BBS of Beam

Bar Bending Schedule of Column BBS

100 IMPORTANT TECHNICAL TERMS ABOUT REINFORCEMENT

 

     

     

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