For understanding the topic of cutting length of stirrups firstly we should know the briefing about what is stirrups ? Stirrups are the rings that are used in column and beam to hold in place the primary reinforcement bar. Actually the rings which are placed in columns are also known as Ties. The use of stirrups is needed to prevent the columns and beams from buckling.
Different types Of Stirrups :-
- Rectangular stirrup
- Circular stirrup
- Diamond stirrup
- Triangular Stirrup
- Hook Bar
Calculation of different Stirrups for length calculation with some imaginary values:-
- Rectangular stirrups
Given:
A = 300 mm , B = 400 mm
Clear cover = 40 mm , Diameter of stirrups = 8 mm
Formula to find cutting length of stirrup = 2 ( l + b ) + 20 D
where D is diameter of bar
A = length of column ( cover is deducted from both side )
B = breadth of column ( cover is deducted from both side )
l = length of stirrups
b = breadth of stirrups
l = A – 2 X cover = 300 – 2 x 40 = 220 mm
b = B – 2 x cover = 400 – 2 x 40 = 320 mm
So put these value in the formula = 2 ( l + b ) + 20 D
Cutting length of stirrup = 2 ( l + b ) + 20 D
= 2 ( 220 + 320 ) + 20 x 8
= 1240 mm or 1.24 m
- Circular Stirrup
GIVEN –
D = Diameter of column = 300 mm
Cover = 40 mm
Diameter of Stirrups = 8 mm
d = Diameter of stirrups
FORMULA TO FIND OUT CUTTING LENGTH OF CIRCULAR STIRRUPSS = (CIRCUMFERENCE OF CIRCLE + 20D) OR (2 PIE R +20D)
CIRCUMFERENCE OF CIRCLE = 2 PIE R OR PIE D
WHERE D = DIAMETER OF COLUMN – 2 X COVER BOTH SIDE
= 300 – 2 X 40
= 220MM
SO PUT THIS VALUE IN THE FORMULA:
CUTTING LENGTH OF STIRRUPS = PIE D + 20D
= 3.14 X 220 + 20 X 8
= 851MM OR 0.851M
- Diamond Stirrups
Given:
A = 400 mm , Clear cover = 40 mm
Diameter of stirrups = 8 mm
Formula to find cutting length of stirrups = 4C + 20 D
where D is diameter of bar
A = length and breadth of column ( cover is deducted from both side )
b = A – 2 x cover = 400 – 2 x 40 = 320 mm
So the value of b is dividing by 2 = b/2 = 320/2 = 160 mm
ACCORDING TO PYTHAGORUS
b/2 = 320/ 2 = 160 mm
C is the inclined length of Diamond Stirrups
C= √ ( 160^2 + 160^2 ) = 226 mm
So put these value in the formula = 4C + 20 D
Cutting length of diamond stirrups = 4C + 20 D
= 4 x 226 + 20 x 8
= 1064 mm or 1.064 m
- Triangular Stirrups
Given:
A = 300 mm , B = 600 mm
Clear cover = 40 mm , Diameter of stirrups = 8 mm
where D is diameter of bar
A = length of column ( cover is deducted from both side )
B = breadth of column ( cover is deducted from both side )
Formula to find cutting length of triangular stirrups = 2C + l + 20 D
l = length of main stirrups
b = breadth of main stirrups
Find out the value
l = A – 2 x cover = 300 – 2 x 40 = 220 mm
e = B – 2 x cover = 600 – 2 x 40 = 520 mm
So the value of e is dividing by 3 portion = e/3 = 520/3 = 173 mm
And also the value of l is dividing by 2 = l/2 = 220/2 = 110 mm
ACCORDING TO PYTHAGORUS
l/2 = 320/ 2 = 160 mm , e/3 = 520/3 = 173 mm
C is the inclined length triangular of Stirrups
C= √ ( 173^2 + 110^2 ) = 205 mm
So put the above value in the formula = 2C + l + 20 D
Cutting length of diamond stirrups = 2C + l + 20 D
= 2 x 205 + 220 + 20 x 8
= 790 mm or 0.79 m
Deduction DONE ON SITE
When we bend the reinforcement bars upto some angle, the bars get stretched and results in the length of the bar getting increased. So we need to deduct the increased length otherwise our steel consumption is more than the required steel as per drawing. We will make this deduction on-site for finding the exact cutting length of the bar. The deduction that we do is according to bend angles.
Different Types Of Bar Bending :-
- Bars with 45º Bend :-
We deduct 1D from the cutting length, i.e. 1D for 45º bend, where D is the diameter of the bar will be deducted from the cutting length.
- Bars with 90º Bend :-
For bars with 90º bend, we deduct 2D from the cutting length, i.e. 2D for 90º bend, where D is the diameter of the bar.
- Bars with 135º Bend :-
For bars with 135º bend, we deduct 3D from the cutting length, i.e. 3D for 135º bend, where D is the diameter of the bar.
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