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Let us make BBS of the pile in a pile foundation as shown below.
As we are making BBS of a pile in the foundation, let us look into the reinforcement details of the pile as shown below.
Given data:
Length of pile =18m.=18000mm.
Diameter of pile = 750mm = 0.75m
Clear cover = 50mm
Pitch = 150 mm. = 0.15m
The diameter of helical stirrup bar = 8mm.= 0.008m.
Main reinforcement. = 16mm.∅ -10 nos.
Master ring =16∅ @ 1800 c/c
Development length Ld = 50d.
Bottom anchorage = 300mm.
Calculation:
A. Cutting length:
1. Vertical reinforcement:
The cutting length of the vertical reinforcement bar
= [ pile depth + development length + bottom anchorage - clear cover - (2nos. × 90° bend )]
= [ 18000mm. + (50d )+ 300mm. - 50mm. - ( 2nos. ×2d)]
= [ 18000mm. + (50 × 16mm) + 300mm. - 50mm. - ( 2nos. ×2 × 16mm)]
= [ 19100mm.- 50mm. - 64mm.]
= 18,986mm.
= 18.986m. >12m.
Hence lapping is required.
As the total length of the bar is less than 24m., there will be 1 lapping for the bar.
The total length of the reinforcement bar required in a pile
= [ calculated cutting length of the bar + ( no. of lapping × lap length )]
= [18,986mm. + ( 1 no × 50d )]
= [18,986mm. + ( 1 × 50 × 16mm. ) ]
= 19,786mm.
= 19.786m.
Cutting length of reinforcement bar-1 = 12m.
Cutting length of reinforcement bar-2
= [19.78m - 12m.] = 7.78m.
2. Master ring:
The cutting length of the master ring
= [2πr + hook length]
Here,
Note: The radius is the pile center to the center of ring circumference ( red dotted line) as shown in the above drawing.
The radius of the master ring r
= [pile dia. - {2nos. × (clear cover + spiral stirrup bar dia. + rebar dia.+(1/2 × master ring bar dia.)}] ÷2
=[750mm. - {2nos.× (50mm. +8mm. + 16mm.+ ( 1/2 × 16mm.)}] ÷2
= [750mm. - {2nos. × 82mm.}] ÷2
= [586mm] ÷2
= 293mm.
The cutting length of the master ring
= [ (2 × 3.142 × 293mm.) + (10d)]
= [ (1841.21mm) + (10 × 16mm)]
= 2001.21mm.
= 2.001m.
3. Spiral stirrup or helix:
The cutting length of the spiral stirrup is covered in detail in a separate article as linked below.
Go through the article👇
👀. How to calculate the cutting length of spiral stirrups(ring).
The cutting length of the spiral stirrup = 255.16m. (Picked from the above article)
B. No. of master ring:
No. of master ring required
= [{( length of pile - clear cover) ÷ c/c distance } + 1]
= [ {(18000mm. - 50mm.) ÷ 1800mm } + 1 ]
= [9.97 + 1]
= 10.97 nos. say 11 nos.
Now, let us prepare a BBS table for a single pile.
|
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. |
Vertical reinforcement. |
16 |
10 |
19.786 |
197.86 |
1.578 |
312.22 |
|
2. |
Helical stirrup. |
8 |
1 |
255.16 |
255.16 |
0.395 |
100.79 |
|
3. |
Master ring. |
16 |
11 |
2.001 |
22.01 |
1.578 |
34.73 |
|
4. |
Total weight of steel bars = |
447.74 |
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|
5. |
Add 3% wastage = |
13.43 |
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|
6. |
The grand total wt. of rebar's in pile = |
461.17 |
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Thank you for going through these calculation steps❤. Have a good day 😄.
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