Bend Deduction length of steel bar as per IS Code 2502-1963

Bend Deduction length of steel bars as per IS Code 2502-1963 as follows

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Bend Deduction as per IS Code

1. How to Calculate Bend deduction in bars as per IS Code 2502-1963?

Fig. 1 shows Value of Radius of arc in IS Code 

calculation is for values

Diameter of bar = 10mm

Angle of bend     = 90 °

By Center line method

Sample calculation is explained 

this shows inner, center and outer arc at corners

Fig. 2 sample calculation by Center line method

 2. How much Bend deduction should we take in BBS for Reinforcement of steel?
for, 8mm, 10mm, 12mm, 16mm = 1*d 20mm, 25mm, 32 mm = 2*d where, d= Diameter of bars

 -After calculation for all the diameter bars, comparison is done for constant values such as 0.9mm, 1.1mm, 1.2mm, 1.5mm, 1.9mm, 2.3mm and 2.9mm

And as per practical experience, is code values, generalized the value for bend Deduction as shown 1d and 2d

This is approximate values because practical for every bars exact value calculation is not possible

-for Bar Bending Schedule BBS bend Deduction is small value so it is not affecting for large quantities

Fig. 3 shows Value of constant for all the bars 

3. Bend Deduction Formula?

Bend Deduction formula 

This is the bend Deduction formula

Where, x= 90° bend distance at corners as shown in figure

Fig.4 shows curve length at corners

4. Why for calculation we are taking centre or neutral axis?

Fig.4 shows inner, Centre and outer arc 

Calculation for 10mm dia,90° bend by Center line method calculation done by taking inner side bar, centre of bar and outer face of bar 

Fig.5 shows calculation for inner, center and outer face of the bars

In this average of value outer and inner face i.e.  (0.86+1 .29)/2 = 1.075 is same as centre value i.e. 1.075

This is the proof as per IS code why we are always taking calculation from Centre of bar or Neutral Axis of bar 

5. Bend Deduction is not about the elongation of the bar 

-as per IS code Bend in corners of the ring/stirrups is because of arc, steel bar is not elongating at all

- this is basic simple mathematics by this we have prooved by sample calculation