How to Make Bar Bending Schedule for Pile Foundation Reinforcement  BBS for Pile  Pile Ring Calculation Formula  Spiral Length Calculation Formula  Pile Helical Reinforcement Formula  BBS of Pile Cap:
In this post, we are going to see Bar Bending Schedule for Pile Foundation Reinforcement  BBS for Pile  Pile Ring Calculation Formula  Spiral Length Calculation Formula  Pile Helical Reinforcement Formula  BBS of Pile Cap.
Pile Foundation Basics
Pile foundations are used in the below situations where the deep foundation is required.
 The Soil is highly compressible and too weak to support the load so we have to reach the hard strata
 The structure has horizontal forces which occur in skyscrapers (wind force)
 Uplifting Force by the excess water table.
 Presence of Expansive soils where soil constantly swells and shrinks like below
Pile Foundation Diagram
Be familiar with typical pile foundation diagram.
It consists of
 Structure
 Pile Cap (supported by number of piles)
OTHER POSTS:

Column Reinforcement Detail  Lateral Reinforcement for Columns  Steel Reinforcement

Bar Bending Schedule Formulas  What is BBS  Bar Bending Schedule with MS Excel
Bar Bending Schedule for Pile Foundation Reinforcement:
We have omitted the pile cap part since is a simple rectangular concrete slab which can be calculated by rectangular volume formula (L X B X h)
As you see in the above diagram
 The pile column should be tied by inner spacer ring and outer helical or spiral ring.
 The Anchorage bar will be bend into the column at bottom
 The Development length is provided outside at top of the column (which will be later inserted into Pile Cap)
From the diagram,
 Height of the pile – 20m or 20000 mm
 Diameter of Pile – 600 mm
 Clear Cover of the pile – 75mm
 Column has 12 numbers of 12mm dia bars
 Inner Spacer Ring (circular ties) – 16mm @ 2000 mm C/C
 Outer Helical Ring – 8mm @ 200mm C/C
 Development Length (Ld) – 40d
 Bottom anchorage length – 300 mm
The Pile has three sections
 Vertical bar
 Inner Spacer Ring
 Outer Helical Ring
Step 1 – Calculate the Length of Vertical Bar:
Cutting length of vertical bar = Pile anchorage length Bottom + Height of Pile + Development Length Upper + Lap Length(50d) – Clear Cover bottom
Formula Explanation:
 As you know from the BBS for Column post, Each rod will be 12.2 m or 39 Feet length. So we have to lap additional bars in order to meet our requirement of 20 m height. That’s why we have added lap length (40d). Always tie the bars at middle, not at upper or bottom where the stress is high
Back to Formula,
Cutting length of vertical bar = Pile anchorage length Bottom + Height of Pile + Development Length Upper + Lap Length(50d) – Clear Cover bottom
= 300mm + 20000 mm + 40d + 50d – 75mm = 300mm + 20000 mm + (40X12) + (50X12) 75mm
= 21.30 m or 21305mm
Total Length of Vertical bar = 21.30 m
Step 2 – Calculation of Number of Inner Spacer Ring & Length of Each Ring:
 Number of Inner Ring = ( Length of Pile / Spacing )+ 1 = (20000 mm/2000 mm) + 1 = 11 Numbers
Length of Each Ring,
Since it is circular figure we have to find the circumference of ring
 Length of Inner spacer ring = Circumference of Inner Ring = 2丌r (where R – Radius)
Now we need to know the radius of inner spacer ring
We already know the diameter of the pile(600mm) so it is easy to find the diameter of inner ring and the radius
Diameter of Inner Ring = Diameter of Pile – Clear Cover – Dia of outer spiral ring – Diameter of vertical bar
= 600mm – 75mm – 8mm – 12mm
Diameter of Inner Ring = 505 mm
Radius of Circle (R) = D/2 Therefore radius of Inner ring = 505mm/2 = 252.5 or 253 mm
Length of Inner Spacer Ring = Circumference of Inner Ring = 2丌r (where R – Radius) = 2 X 3.14 X 253mm
Length of Inner Spacer Ring = 1588 mm or 1.59 m
Step 3 – Calculation of Number of Outer Helical Ring & Length of Each Ring:
From the Diagram,
 Length of Pile – 20 m or 20000 mm
 Diameter of Pile – 600 mm
 Spacing of Outer Helical Ring – 200 mm
 Diameter of Helical Ring – 8mm
Again as above in order to find the length of the helical outer ring we have to find the circumference of the ring
 Length of Inner spacer ring = Circumference of Inner Ring = 2丌r (where R – Radius)
We already know the diameter of the pile(600mm) so it is easy to find the diameter of inner ring and the radius
Diameter of outer spiral ring = Diameter of Pile – Clear Cover = 600mm – 75mm = 525mm
Therefore Radius of spiral ring (R) = D/2 Therefore radius of Inner ring = 525mm/2 = 262.5 or 263 mm
Length of One spiral ring = Circumference of Inner Ring = 2丌r (where R – Radius) = 2 x 3.14 X 263mm
Length of one spiral ring = 1652 mm or 1.65 m
Now we have to find how many number of spiral ring we need
Required Number of Spiral Rings = ( Length of Pile / Spacing ) + 1 = (20000 / 200) + 1 = 101 spirals or numbers
Bar Bending Schedule Table for Pile Reinforcement:
Conclusion:
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