Bar Bending Schedule Basic Formulas | BBS Formula | What is BBS | Hook Length | Cut Length of Straight Bar | Cut Length of Bend up Bar or Crank Bar | Length of Extra Bars | Hook’s Length Formula for Stirrups | Lap Length:
In this Article today we will talk about the Bar Bending Schedule Basic Formulas | BBS Formula | Hook Length | Cut Length of Straight Bar | Cut Length of Bend up Bar or Crank Bar | Length of Extra Bars | Hook’s Length Formula for Stirrups | Lap Length. These are the important Tips to make and find the steel cutting length.
What is Bar Bending Schedule?
In Civil Engineering Bar Bending Schedule is the important part of Estimation chart. In the Bar Bending schedule provides the reinforcement (steel) calculation for reinforcement of concrete column , beam and slab cutting length and also use to find the types of bends of length which we provide in steel structures.
BBS is used in finding cutting length of steel and total weight of steel per unit area. and we can make the bar bending schedule in Ms office Excel software.
Bar Bending Schedule Basics Formula | Calculation of Reinforcement Shape, Cutting and Bending Lengths:
1. Hook Length:-
The hook length is commonly provided for stirrups
Hook Length = 9D [D is Diameter of the Bar]
Total Length of stirrup = Total length of Bar + 2 x Hook Length (Two hooks)
Total Length = L+2(9D)
Therefore Total length = L+18D (D is Diameter of bar)
2. Length of Straight Bar with Bends:-
Total Length = Length of Straight Portion + 2(Hook Length)
3. Additional Length for Bent up or Crank Bar with Bends:-
The additional length (la) that is introduced in the simple, straight end-to-end length of a reinforcement bar due to being bent up at (Theta) say 30o to 60o, but it is generally 45o = l1 – l2 = la
Giving different values to respectively), we get different values of la, as tabulated below:
Figure 2 presents the procedure to arrive at the length of hooks and the total length of a given steel reinforcement.
For 45 Deg | Crank length is provided in Slab Shear stress is maximum at supports in Slab. So, to resist this stress we usually crank the bars at the ends of supports in slab.
Crank bar is bent up at an angle of 45 degree with the length of 0.42D
D = Depth of Slab-Top Cover-Bottom cover
4. Length for Extra Bars:-
Now a days Extra bar is also provided under every crank bar. To keep crank bar in position. (Refer above image for clear idea).
5. Bend Hook Length Formula for Column:-
Bend Length is usually provided in columns at ends to tie the columns to the footings.
Bend Length = 16D [D is Diameter of the Bar]
7. Hook’s Length Formula for Stirrups:-
Hook’s Length for Stirrups are mostly equal to 10d, Where d is dia of bar.
Rectangular Stirrups | Length of Stirrups = 2A + 2B + (2 x 10d)
Triangular Stirrups | Length of Stirrups = 3H + (2 x 10d)
Circular Stirrups | Length of Stirrups = (3.142 x Dia of Steel Ring) + (2 x 10d)
Diamond Stirrups | Length of Stirrups = 4H + (2 x 10d)
Spiral Stirrups | Length of Stirrups = Length of Spiral or Helix Bar = n x (C2 + P2)^0.5
- n = No. of Pitches = n = H/p + 1
- C = 3.142 x d
- P = Pitch or Spacing between spirals
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