How to calculate bar Bending Schedule for Slab | One way and Two way

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Before calculation of bar bending schedule for one way and two-way slab, I would like to suggest you read the article “What makes one-way slab and two-way slab different from each other

If you have already read you can proceed to the calculation otherwise it will be difficult for you to know some technical terms related to one-way and two-way slab.

Now, let us how to calculate bar Bending Schedule for Slab.

A) Bar Bending Schedule of One way Slab

How to calculate bar Bending Schedule for Slab | One way and Two way

Before bar bending schedule of Slab first of you should know that in one way slab the main bars ie. The cranked bar is provided in shorter direction and distribution bar is provided in longer direction but in two way slab, the cranked bars is provided in both direction.

Bars used in one way and two way slab.

Distribution bars:- 

These bars are straight bars.


Main bars:- 

These bars are cranked bars. Main bars are cranked at an angle of 45 Degree with the length of 0.42D

Where, D = Depth of Slab- Top cover – Bottom cover

Extra Bars:-

The extra bar is provided at the bottom of Cranked bars to maintain the framework of the slab.
The length of Extra bar is L/4.

Steps to calculate the Reinforcement required for Slab:-

  1. Calculate the length of distribution and main bars subtracting the clear cover of the slab.
  2. Calculate
  3. Calculate the Value of ‘D’ (Depth of slab- Top cover- Bottom cover)
  4. Find out the No. of Bars
  5. Compute the Total weight of steel required for slab reinforcement.
How to calculate bar Bending Schedule for Slab | One way and Two way
How to calculate bar Bending Schedule for Slab?

One way slab Reinforcement Detailing

Given,

  1. Cranked bars or Main bar of diameter 16 mm and center to center spacing 150 mm.
  2. Distribution bars of diameter 12 mm and center to center spacing 150 mmm.
  3. Top and bottom clear cover of slab is 20 mm.
  4. Side clear cover of slab 25 mm
  5. Thickness of slab is 150 mm.
  6. Length of slab is 5000 mm (longest side along beam)
  7. Width of slab (Clear Span) without beam is 2000 mm. (shortest side perpendicular to beam)
  8. Length of top extra bar = L/4 = 2000/4 = 500 mm
  9. No. of top extra bars = No. of Main bars
  10. Diameter of top extra bars

Now,

For Main bars,

How to calculate bar Bending Schedule for Slab | One way and Two way

Step:- 1 Calculate numbers of main rods.

No. of Main rods = (Length of Slab)/ Spacing + 1

No. of Main rods = (5000)/150 + 1

No. of Main rods = 34.33 No. = Say 35.

Step:- 2 Calculate cutting length of one main rods.

Cutting length of one crank bars = Clear span of slab + ( 2 x Development length) + (1 x inclined length) – (2 x 45 Bend)

Cutting length of crank bars = 2000 + ( 2 x 40d) + (1 x 0.42D) – (2 x 1d)

(Since, Development length = 40d, inclined length = 0.42D, 45 Bend= 1d)

Where,

D = Thickness of slab – 2 x Side clear cover – diameter of bars

D = 150 – 2 x 25 – 16 = 84 mm

Cutting length of one crank bars = 2000 + ( 2 x 40 x 16) + (1 x 0.42 x 84) – (2 x 16)

Cutting length of one crank bars = 3283.28 mm

Step:- 3 Calculate Total length of main rods.

Therefore Total length of crank bars = Length of one crank bar  x  No. of crank bars

Total length of crank bars = 3283.28 x 35 = 114914.8 mm = 114.9148 meter.

Step:- 4 Calculate total weight of main rods.

W1 = (d2 / 162.25) x Length

W1 = (162 / 162.25) x 114.9148

W1 = 181.31 kg

For Distribution bars,

Step: – 1 Calculate numbers of distribution rods.

No. of Main rods = (Width of Slab/Spacing) + 1

No. of Main rods = (2000)/150 + 1

No. of Main rods = 14.33 No. = Say 15.

Step: – 2 Calculate cutting length of one distribution rods.

Cutting length of one distribution bars = Length of Slab + 2 x development length

Cutting length of one distribution bars = 5000 + 2 x 40d

Cutting length of one distribution bars = 5000 + 2 x 40 x 12

Cutting length of one distribution bars = 5960 mm = 5.960 meter

Step:- 3 Calculate Total length of distribution rods.

Therefore Total length of crank bars = Length of one crank bar  x  No. of crank bars

Total length of crank bars = 5960 x 15 = 89400 mm = 89.400 meter.

Step:- 4 Calculate total weight of distribution rods.

W2 = (d2 / 162.25) x Length

W2 = (122 / 162.25) x 89.400

W2 = 79.34 kg

For Top Extra bars,

Length of top extra bar = L/4 = 2000/4 = 500 mm

No. of top extra bars = No. of Main bars = 35

Total length of Top extra bars = 500 x 35 = 17500 mm = 17.500 meter

Therefore total weight of top extra bars = W3

W3 = (162 / 162.25) x 17.500

W3 = 27.61 Kg

Final Step,

Hence,

Total Weight of Steel Rod = Total Weight of crank bars + Total Weight of Distribution bars + Total weight of extra top bars

Total Weight of Steel Rod = 181.31 kg + 79.34 kg + 27.61 kg = 288.26 kg

B) Bar bending schedule of two-way Slab

How to calculate bar Bending Schedule for Slab | One way and Two way

Two way slab Reinforcement Detailing

How to calculate bar Bending Schedule for Slab | One way and Two way
How to calculate bar Bending Schedule for Slab?

Given,

  1. Length of slab (along X-Direction) is 3000 mm (longest side)
  2. Cranked bars or Main bar (along X-Direction) of diameter 16 mm and center to center spacing 150 mm.
  3. Width of slab (along Y-Direction) is 2000 mm. (shortest side)
  4. Cranked bars or Main bar (along Y-Direction)of diameter 16 mm and center to center spacing 150 mm.
  5. Top and bottom clear cover of slab is 20 mm.
  6. Side clear cover of slab 25 mm
  7. Thickness of slab is 150 mm.
  8. Length of top extra bar = L/4 = 2000/4 = 500 mm
  9. No. of top extra bars = No. of Total Crank bars
  10. Diameter of top extra bars = 16 mm.

Now,

For Main bars along X-Direction,

Step: – 1 Calculate numbers of main rods.

No. of Main rods = (Length of Slab) / Spacing + 1

No. of Main rods = 2000/150 + 1

No. of Main rods = 14.33 No. = Say 15.

Step:- 2 Calculate cutting length of one main rods.

Cutting length of one crank bars = Clear span of slab + ( 2 x Development length) + (1 x inclined length) – (2 x 45 Bend)

Cutting length of crank bars = 3000 + ( 2 x 40d) + (1 x 0.42D) – (2 x 1d)

(Since, Development length = 40d, inclined length = 0.42D, 45 Bend= 1d)

Where,

D = Thickness of slab – 2 x Side clear cover – diameter of bars

D = 150 – 2 x 25 – 16 = 84 mm

Cutting length of one crank bars = 3000 + ( 2 x 40 x 16) + (1 x 0.42 x 84) – (2 x 16)

Cutting length of one crank bars = 4283.28 mm = 42.832 meter

Step:- 3 Calculate Total length of main rods.

Therefore Total length of crank bars = Length of one crank bar  x  No. of crank bars

Total length of crank bars = 4283.28 x 15 = 64249.2 mm = 64.249 meter.

Step:- 4 Calculate total weight of main rods.

W1 = (d2 / 162.25) x Length

W1 = (162 / 162.25) x 64.249

W1 = 101.37 kg

For Main bars along Y-Direction,

How to calculate bar Bending Schedule for Slab | One way and Two way

Step:- 1 Calculate numbers of main rods.

No. of Main rods = (Length of Slab) / Spacing + 1

No. of Main rods = 3000/150 + 1

No. of Main rods = 21 No.

Step:- 2 Calculate cutting length of one main rods.

Cutting length of one crank bars = Clear span of slab + ( 2 x Development length) + (1 x inclined length) – (2 x 45 Bend)

Cutting length of crank bars = 2000 + ( 2 x 40d) + (1 x 0.42D) – (2 x 1d)

(Since, Development length = 40d, inclined length = 0.42D, 45 Bend= 1d)

Where,

D = Thickness of slab – 2 x Side clear cover – diameter of bars

D = 150 – 2 x 25 – 16 = 84 mm

Cutting length of one crank bars = 2000 + ( 2 x 40 x 16) + (1 x 0.42 x 84) – (2 x 16)

Cutting length of one crank bars = 3283.28 mm

Step:- 3 Calculate Total length of main rods.

Therefore Total length of crank bars = Length of one crank bar  x  No. of crank bars

Total length of crank bars = 3283.28 x 21 = 68948.88 mm = 68.948 meter.

Step:- 4 Calculate total weight of main rods.

W2 = (d2 / 162.25) x Length

W2 = (162 / 162.25) x 68.948

W2 = 108.78 kg

For Top Extra bars,

Length of top extra bar along X-Direction = L/4 = 3000/4 = 750 mm

No. of top extra bars = 15 Nos.

Total Length = 750 x 15 = 11250 mm = 11.250 meter

Length of top extra bar along Y-Direction = L/4 = 2000/4 = 500 mm

No. of top extra bars = 21 Nos.

Total Length = 500 x 21 = 10500 mm = 10.500 meter

Therefore,

Total length of Top extra bars = 11.250 meter + 10.500 meter = 21.75 meter.

Therefore total weight of top extra bars = W3

W3 = (162 / 162.25) x  21.75

W3 = 34.31 Kg

Final Step,

Hence,

Total Weight of Steel Rod = Total Weight of crank bars (along X-direction) + Total Weight of main bars (along X-direction) + Total weight of extra top bars

Total Weight of Steel Rod = 101.37 kg + 108.78 kg + 34.31 kg = 244.46 kg

I hope this article on “How to calculate bar Bending Schedule for Slab” remains helpful for you.

Happy Learning – Civil Concept

Contributed by,

Civil Engineer – Ranjeet Sahani

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