How to calculate the lengths of steel bars
The lengths of steel bars are provided for the following items :-
- 900 Bend
- 1800 Bend
- Overlap
- For Bent up bars
- Lateral ties or vertical stirrups
- Bent-up and hook
900 Bend
- Extra length for one bend = 4D
- So, length of bar = L + 4D (Here, D denotes for Dia)
Also read : PERMISSIBLE STRESSES IN CONCRETE AND STEEL REINFORCEMENT
1800 Bend
- Cover is taken as B and diameter of bar is taken as D.
- Additional length for each hook = 9D
- If hook is located at one end, total length of bar = L + 9D
- If hook is located at both ends, total length of bar = L + 9D + 9D
Overlap
- For bars in tension
- For bars in compression
- Additional length = 40D + 9D + 9D = 58D (for mild steel bars) and 68.5D (for deformed steel bars)
- Additional length = 45D (for mild steel bars)
For bent up bars
- CD = x/sinθ - xtanθ = x[1/ sinθ - 1/tanθ]
- When the bar is bent up at 450, θ = 450
- So, CD = x [1.414 - 1.0] = 0.414x = 0.45x
- So, for bar that is bent up at 450, extra length = 0.45x
Bent-up and hook
- Length of two hooks = 9D + 9D
- Additional length for one bent = 0.45X
- So, total length of bar = L + 9D + 9D + 0.45X
Number of bars
- Space = Distance inside which bars should be placed = L - 2 x cover
- So, number of bars = (L - 2 x cover) / c/c spacing of bars
- Number of stirrups in a beam
- = Length of beam - 2 x cover / c/c spacing of stirrups + 1
Weight of the bar for 1m length
- Weight of reinforcement bar for 1m length = d2 / 162 kg
- Here, d denotes diameter of bar in mm
