BBS of Beam | Bar Bending Schedule of Beam

BBS in civil engineering stands for bar bending schedule of the rebar for different structural members like beam, column and, slab. Here we will discuss about BBS of beam. Before this let us discuss, why we need BBS of beam, column, slab etc in short.

Why BBS of Beam is necessary?

Bar bending schedule of the rebar is required due to the following reasons.

• It shows information on the types of rebar used for different portions of the structure.
• It helps to know the cutting length and total length of the rebar used for the structure.
• It helps to estimate the weight of the rebar.
• It helps to know the shape and size of the rebar.

Now, let us see stepwise calculation of bbs for beam with example.

How to Calculate BSS of Beam?

Let us we have section of the beam having width x depth as 250 mm x 300 mm respectively. Rebar used in beam are 4 nos. of 16 mm at corners and 2 nos. of 12 mm as top and bottom extra. Clear Cover provided is 25 mm each side. The clear span of the beam is 23 feet.

The stirrups used in the beam are of diameter 8 mm. Now Calculate the BBS of Beam.

Here we Have,

Diameter of Corner Rebar is 4 Nos. of 16 mm.

Diameter of Top and Bottom extra Rebar is 2 Nos. of 12 mm.

Diameter of Stirrups is of 12 mm.

Step 1:- Calculate total length of Main/Corner rebar, Top/Bottom extra rebar and stirrups.

Corner Bar (4 – 16 mm)

Cutting length of Single Rebar,

= Length of the beam + Development length- Bend

Here, Development length is the embedded part of rebar in column which should be added in clear span of beam and Bend is the stretched part of rebar while bending which should be deducted.

Generally, we provide 50D as a development length where D is the diameter of the rebar. and Bend length deduction depends upon the angle of rebar bending given as below.

(Read about Development length in Detail)

= (23/3.28*1000 )+ 2*50*16 – 2*2*16

=8548.2 mm or 8.54 m

So, Length of Total Corner Rebar,

= 8.54 m x 4 = 34.2 meter

Simillarly,

Top and Bottom Extra Bar (2- 12 mm)

Cutting length of Single Rebar,

= Length of the beam + Development length- Bend

= (23/3.28*1000 )+ 2*50*12 – 2*2*12

=8164.19 mm or 8.16 m

So, Length of Total Corner Rebar,

= 8.16 m x 4 = 16.3 meter

Now,

For Stirrups (8 mm)

Cutting length of Single Rebar,

= 2 x (Width of Beam-Clear Cover)  + 2 x (Height of Beam Beam-Clear Cover )+ 2 x Hook Length – Bends

(Here, we have clear cover of beam is 25 mm)

= 2 x (250-25)  + 2 x (300-25 )+ 2 x 70 – (4 x2D+2 x 3D)

= 2 x (250-25)  + 2 x (300-25 )+ 2 x 70 – (4 x2 x8 + 2 x 3 x 8)

= 1030 mm = 1.03 meter

Here,

Total No of stirrups,

= Span/150 = (23/3.28*1000 )/150

= 46.74  = 47 Nos.

Total Length of Stirrups,

= No of stirrups x Length of single stirrups

= 47 x 1.03

= 48.41 meter

Step 2:- Calculate total Weight of Main/Corner rebar, Top/Bottom extra rebar and stirrups.

Now Calculate Total Weight of Rebar,

Weight of 16 mm corner rebar,

Wc = L x D x D/162.25

= 34.2 x 16 x 16/ 162.25

= 53.96 Kg

lly,

Weight of 12 mm extra rebar,

Wc = L x D x D/162.25

= 16.3 x 12 x 12/ 162.25

= 14.4 Kg

Weight of Stirrups,

Ws = L x D x D/162.25

= 48.41 x 8 x 8/ 162.25

= 19 Kg.

Step 3:- Add all weight and calculate total Weight of Rebar

Summary,

Weight of 16 mm rebar = 53.96 Kg.

Weight of 12 mm rebar = 14.4 Kg

Weight of 8 mm rebar = 19 Kg.

Total = 53.96 Kg. + 14.4 Kg + 19 Kg. = 87.36 Kg.

Summary Table of BBS of Beam

I hope this article on BBS of Beam remains Helpful for you.

Civil Concept

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