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How to calculate Cutting length of Stirrups in Beam and column

How to calculate Cutting length of Stirrups in Beam and column

STRUCTURE 15 Comments

To cater the stresses and loads in RCC, Bars are bent to different shapes in the bar bending schedule.

Different shapes of bars have different cutting length. In this post, we are going to explain you about “How to calculate or find the cutting length of Stirrups for different shapes”.

Remember,

The transverse reinforcement provided in Column is called Ties and the transverse reinforcement provided in Beam is called Stirrups. But on-site, we usually call both transverse reinforcements as Stirrups.

The prime reason for providing the stirrups in the beam is for shear requirements and to keep the longitudinal bars in position. If you wanted to know more about the why stirrups & ties provided in the beam and column you can refer here

Deducting the concrete cover is most important in Bar bending, if you dont know how to deduct the concrete cover then refer this post

Concrete Cover deductions in Beams, Columns, Slab, Footings

Steps involved in finding the cutting length of stirrups:-

  1. Look at the size of column or beam from drawings
  2. Adopt Dia of the bar (generally 8mm Dia is used for stirrups)
  3. Deduct the concrete cover or clear cover
  4. Find the total outer length of stirrup after deducting concrete cover.
  5. Add the length of the hook to the length of the stirrup
  6. Deduct the length of bends
  7. Use below formula to find the total cutting length of stirrups

Formula: 

Cutting Length of Stirrups = Perimeter of Shape + Total hook length – Total Bend Length

Important Basic formulas:

Perimeter of Rectangle = 2 ( length + breadth)

Perimeter of Square = 4 x side length

Perimeter of circle or Circumference of Circle = 2πr = πd (r= radius, d= Diameter of Circle)

Typical Diagram of Stirrup:-

Refer the below image of the typical diagram of stirrup for clear understanding about x & y length, bends, hooks and concrete cover.

typical stirrup diagram

In the above image, there are 5 bends at 4 corners, 2 hooks and concrete cover around the stirrup.
x = length of the stirrup in the x-direction after deducting concrete cover &
y = length of the stirrup in the y-direction after deducting concrete cover.

Important standards used in Bends & Hooks:

The below standards are most important in calculating the hook length and bend lengths at corners while finding cutting length of stirrups.

  • 1 Hook length = 9d or 75mm
  • 45° Bend length = 1d
  • 90° Bend length = 2d
  • 135° Bend length = 3d

Remember, d = Diameter of Bar

Cutting length for Rectangular Stirrups:-

Rectangular column or rectangular beam is the most commonly used shape of the column in any construction. In this shape of beam or column, a rectangular stirrup is usually adopted.

  1. Considering the below Rectangular column size 230mm x 450mm for calculation purpose
    rectangular column details
  2. Adopting Dia of Bar used for stirrups is 8mm
  3. Deducting the concrete cover 20mm from all sides
    x = 230 – 20-20 = 190mm
    y = 450-20-20 = 410mm
    cutting length of rectangular stirrup
  4. Total Length of the hooks:
    From fig, There are two hooks which means 9d+9d = 18d
  5. Total Length of Bends:
    From above fig, There are 3 bends which are bent at an angle of 900 and two bends are bent at an angle of 1350
    Total bend length = 3 x 900 Bend length + 2 x 1350 Bend length = 3 x 2d + 2 x 3d = 12d = 12 x 8 = 96mm

Total Cutting length of Rectangular Stirrup = Perimeter of Rectangle + Total Hook length – Total Bend Length

= 2 (x+y) +18d – 12d = 2(190 + 410) + 18 x 8 – 12 x 8 = 1248mm = 1.248m

Cutting length for Square Stirrups:-

  1. Considered the column size as 450mm x 450mm
    square stirrup details
  2. Adopting Dia of Bar used for stirrups is 8mm
  3. Deducting the concrete cover 25mm from all sides (in square all sides are equal)
    x = 450- 20-20 = 410mm
    y = 450-20-20 = 410mm, Hence x = y (in square all sides are equal)
    Square stirrup deductions
  4. Total Length of the hook:
    There are two hooks which mean 9d+9d = 18d
  5. Total length of Bends:
    There are 3 bends which are bent at an angle of 900 and one is bent at an angle of 1350.
    Total bend length = 3 x 900 Bend length + 2 x 1350 Bend length = 3 x 2d + 2 x 3d = 12d = 12 x 8 = 96mm
    square stirrup details

Total Cutting length of Square Stirrup = Perimeter of Square + Total Hook length – Total Bend Length

= 4 x 410 +18d – 12d = 1648mm = 1.64m

Cutting Length for Circular Stirrup:

  1. Considered the column dia as D = 1000mm
  2. Adopting Dia of Bar used for stirrups is d =8mm
    Circular Stirrups details
  3. Deducting the concrete cover from diameter of column
    D = 1000-25-25 = 950mm
    circular stirrup with hooks and bends
  4. Circumference length of Ring = πD = 950 x 3.14 = 2983mm
  5. Total Length of the hook:
    There are two hooks which means 9d+9d= 18d
  6. Total Length of Bends:
    There are 2 bends which are bent at an angle of 1350
    Total bend length = 2 x 1350 Bend length = 2 x 3d = 6d= 6 x 8 = 48mm

Total Cutting length of Circular Stirrup or Ring = Circumference of Circle + Total Hook length – Total Bend Length
= 2983 +18d – 6d =3079mm =3.07m

Cutting Length for Triangular Stirrups:

  1. Considered the Column size 400mm x 450mm
    traingular stirrup details
  2. Adopting Dia of Bar used for stirrups is d = 8mm
  3. Deducting the concrete cover 25mm from all sides
    x = 400-20-20 = 360mm
    y = 450-20-20 = 410mm
    From Pythagorean theorem,
    Hypotenuse2=(Opposite)2 + (Adjacent)2 
    finding hypotnuse in triangular stirrup
    look at 2nd triangle in above image
    H2=(x/2)2 + y2
    H2=1802 + 4102 => =  √(447)2  = 447mm
    The total length of stirrup till now = 2 x H + 360 = 2 x 447 + 360 = 1254mm
  4. Total Length of the hooks: 
    There are two hooks which means 9d+9d= 18d
    Triangular stirrup Hooks and Bend Lengths
  5. Total length of Bends:
    There are 4 bends which are bent at an angle of 1350
    Total bend length =4 x 1350 Bend length=  4 x 3d = 12d= 12 x 8 = 96mm

Total Cutting length of Triangular Stirrup = Perimeter of Triangle + Total Hook length – Total Bend Length

= 1254+18d – 12d = 1302mm = 1.3m

Cutting Length for Diamond Stirrups:

  1. Considered the Column size 400mm x 400mm
    diamond stirrup details
  2. Adopting Dia of Bar used for stirrups is d = 8mm
  3. Deducting the concrete cover 25mm from all sides
    x = 400-20-20 = 360mm
    y = 400-20-20 =360mm
    diamond stirrups hook length and bend length
    From Pythagorean theorem,
    Hypotenuse2=(Opposite)2 + (Adjacent)2 
    H2=(x/2)2 +( y/2)2
    H2=1802 + 1802 => =  √(254)2  = 254mm
  4. The total length of stirrup = 4 x H  =4 x 254 = 1016mm
  5. Total Length of the hook:
    There are two hooks which means 9d+9d= 18d
  6. Total length of Bends:
    There are 3 bends which are bent at an angle of 900  + 2 bends which are bent at an angle of 1350
    Total bend length = 3 x 900 Bend length + 2 x 1350 Bend length= 3 x 2d + 2 x 3d = 12d = 12 x 8 = 96mm

Total Cutting length of Diamond  Stirrup = Perimeter of Diamond shape + Total Hook length – Total Bend Length
= 1016+144-96 = 1064mm = 1.064mm

 

Read more about how to Estimate the Quantities of Steel (Bar Bending Schedule) for different members of a structure:

I hope now you can easily find the cutting length for different types of stirrups.

If you have any doubts you can post them on our Forum

 

 

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15 Comments

  1. Taoheed December 23, 2018 Reply

    This is brilliant

  2. serwanga david April 13, 2019 Reply

    Thank u for the teaching to all viewers ,that tend to add on the impact to those who has taken long while missing the field works.
    For calculation on my side is not abig problem I quantify it proper.

    • Aitesham ansari March 22, 2020 Reply

      Thank you… Good information is covered in this topic…

  3. Mashud Marly June 10, 2019 Reply

    For finding the hook length and bend length, the ‘d’ used here is dia of steel for making stirrups.(8mm here)

    In actual the dia of the steel(vertical steel provided) on which the ring/stirrup is the touching has to be used(12mm 16mm 20mm as per drawing spec) , as the size of column steel differs the bend length and hook length will be changed.

  4. babu June 10, 2019 Reply

    well

  5. Paul November 13, 2019 Reply

    Thanks for the post and teaching. Please I will like to ask, how come the standard for hook length is 2/9/diameter of stirrup. What does the 2 and 9 stand for.

  6. FARHA NAZNI November 28, 2019 Reply

    Good explanation sir …but concrete cover 20mm ,25mmm actual concrete cover …I CONFUSE

  7. umesh kk January 7, 2020 Reply

    Thank you sir for the valuable informations

  8. H K Mallikarjun July 5, 2020 Reply

    Thank you so much sir for providing detailed information

  9. Ahmad Meher August 23, 2020 Reply

    Sir the db you used here is the dia of stirrups or the dia of main bars. Sir i think it will be a dia of main bars because the bend length and hook length changes with dia of main bar. Sir please inform me about this. I am confuse. Thank you.

  10. SELVAKUMAR September 11, 2020 Reply

    USEFUL ARTICLE SIR

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