What Is a Bar Bending Schedule | Preparation as Per Bs 4466 | Tolerances as Per Bs 4466
Civil

What Is a Bar Bending Schedule | Preparation as Per Bs 4466 | Tolerances as Per Bs 4466

Bar Bending Schedule

What Is a Bar Bending Schedule?

Bar bending is calculating of steel quantity that calls bar bending schedule.

The preparation of bar bending schedules is one of the final stages in any concrete design following the preparation and detailing of the working drawings.

Whereas the procedure is generally straightforward, it does require a certain amount of calculation which can readily be carried out with the aid of a computer program.

The program in this section calculates the lengths of reinforcing bars required and outputs a bar bending schedule table together with the total weight of steel.

Also, read: What is Plum Concrete | Application | Mix Design | Methodology

 

Why Calculating of Bar Schedule?

  • A requirement of steel in the project
  • Labor cost
  • Project monitoring
  • Material reconciliation
  • Contol of Wastage in steel etc..

As per the above point reason of bar bending schedule.

Also, read: Lab Test on Aggregates at Site

Preparation of Bar Bending Schedule as Per Bs 4466

As per BS (British Standard) 4466:1989

    • Form of Schedule as Per Bs 4466
    • Form of Fabric Schedule
    • Preferred Shapes, Their Method of Calculation and Measurement of the Length
    • Other Shapes, Their Method of Calculation and Measurement of the Length
    • Minimum Former Radii, Book and Bend Allowances
    • Scheduling 
    • Bends and Hooks
    • Tolerances on Cutting and Bending Dimensions
  • Form of Schedule as Per BS 4466

 

BS 4466

From of Bar Schedule

  • Form of Fabric Schedule as Per BS 4466

Form of fabric schedule

Form of fabric schedule

Also, read: Concreting in Construction | Classification | Properties | Grades | Advantage & Disadvantage | Quality Control

  • Preferred Shapes, Their Method of Calculation and Measurement of the Length

Shape codeMethod of measurement of bending dimensionsTotal length of bar (L) measured along centreline
20AA
32bA + h
33CA + 2h
34DA + n
Where the overall dimension of the bob is critical, use shape code 37
3535A + 2n
Where the overall dimension of either bob is critical, do not use this shape code
3737A + (B) –½r–d
This formula is approximate Where r is greater than the minimum value inTable 3 use shape code 51
3838A + B + (C) –r –2d
4141If angle with the horizontal are 45° or less,A + B + (C)
length formula is near about and when bending angles exceed 45 ° the length could be calculated more accurately allowing for this difference between the specified overall the true length and dimensions measured along the central axis of this bar or wire.
4343If angle with the horizontal are 45° or less,A + 2B + C + (E)
length formula is near about and when bending angles exceed 45 ° the length could be calculated more accurately allowing for this difference between the specified overall the true length and dimensions measured along the central axis of this bar or wire.
5151A + (B) –1/2R – d
This formula is approximate R is minimum, use shape code 37If R is greater than 200 mm
61612(A + B)+ 12d
Neither A nor B are to be less than 12d or 150 mm, whichever is the greater, for grade 460 in size not exceeding 20 mm nor less than 14d for size of 25 mm and over Neither A nor B are to be less than 10d for grade250 with a minimum value of A and B of 100 mm
6262If angle with the horizontal is 45° or less,A + (C)
82822A + 3B + 18d
If B is greater than 400 + 2 d

Table: 1

Also, read: Total Station in Surveying | Operations | Advantage & Disadvantage | Types

  • Other Shapes, Their Method of Calculation and Measurement of the Length

Shape codeMethod of measurement of bending dimensionsTotal length of bar (L) measured along centreline
3939A + 0.57B + (C) –1.57dIf B is greater than400 + 2d,
If B is greater than 400 + 2d
4242If the angle with horizontal is 45° or less,
A + B + C + n
4545If the angle with horizontal is 45° or less
A + B + (C) –1/2r –d
4949If the angle with horizontal is 45° or less,
A + B + (C)
5252A + B + C + (D) –11/2r–3d
5353A + B + C + D + (E) –2r –4d
5454A + B + (C) - r + 2d
5555A + B + C + D + (E) - 2r - 4d
6565A
77772A + B + 20d
78782A + B + C +3d
79792A + 3B + 10d
Neither A nor B aren't to be more than 12dor150mm, whichever is the greater, for grade460in sizes not exceeding 20 mm more than 14d for sizes of 25 mm and over. Neither A nor B aren't to be more than 10d for grade250 with a minimum value of A and Bof100mm
85
85A + B + 0.57 C + (D) – 1/2r –2.57d
IfCisgreaterthan 400 + 2d
8787Where B is not greater than A/5
(C/B)π(A-d) (L≤12m)

where
A is the external dia (in mm)B is the pitch in helix (in mm)C is the overall height in helix (in mm)there B is greater than A/5 the formula doesn't apply. There may be at least two full turns in the helix.

Table: 2

Also, read: What Is Raft Foundation | Type of Footing | Detail of Raft Footing

  • Minimum Former Radii, Book and Bend Allowances

table

 

Bar size Grade and Type  R and type and grade S Grade and Type  T and type and grade S Fabric complying from BS 4483
d r n h r n h d r n h
6a 12 100 100 18 100 100 5 15 100 100
8 16 100 100 24 100 100 6 18 100 100
10 20 100 100 30 100 110 7 21 100 100
12 24 100 110 36 100 140 8 24 100 100
16 32 100 150 48 100 180 9 27 120 135
20 40 100 180 60 110 220 10 30 120 135
25 50 130 230 100 180 350 12 36 130 145
32 64 160 290 128 230 450
40 80 200 360 160 280 560
50a 100 250 450 200 350 700

Table: 3

Also, read: What is Chain Surveying (Principal, Procedure, Method, Instrument)

Scheduling

    • Each sheet or bar of fabric should be scheduled completely and without any reference to earlier schedules. Such as descriptions  “See schedule 12” or “As before” shall not be used
    • The preferred shape codes to be used shall be as given in Table 1. Table 2 gives other shape codes that may be required. Shapes that do not have a specific shape code number given in Table 1 or Table 2
    • For shapes without an end anchorage, the
      dimension shown in parentheses in Table 1 and Table 2 shall be the variable dimension to allow for the permissible deviations
    • No dimension given in Table 1 or Table 2 shall be given a zero value, as this changes the basic shape.
    • If the angle between both portions of the shaped meeting at a bend isn’t a right angle, it should be given and shall be defined by co-ordinates and not by degrees of arc.
    • The overall off-set dimension of a crank should be not less than twice the size of the bar or wire. The angled length as shown in Figure 6 shall be not less than 10d for grade 250 nor less than 12d for grade 460 in sizes of less than 20 mm nor less than 14d for grade 460 in sizes of 25 mm and over.
    • Or all shapes with two or more bends into the same or opposite directions, the overall dimension is given on the schedule shall always include a minimum straight of 4d between the curved portion of the bends, as shown in as per below figure. The value of x in as per below figure  shall be not less than the following:

Example of bar with more thanonebend

Example of a bar with minimum than one bend
a) 10 d for grade 250 material;
b) 12 d for grade 460 material not exceedingly sizes of 20mm;
c) 14 d for grade 460 material in sizes of 25mm and over.
    • The minimum length of material to be given on this schedule to form a hook or bend shall be as given for n or h respectively inTable 3.

Also, read: What Is Bulkage of Sand (Fine Aggregate )

Bends and Hooks

  • Before taking into account the cumulative cutting tolerances, the nominal value for in table 3 shall be calculated as follows:
    • For a bend, n – 0.57r+ 0.21d;
    • For a hook, h–2.14r– 0.57d

Tolerances on Cutting and Bending Dimensions

  • The tolerances given in Table 4 shall apply for cutting and/or bending dimensions and should be taken in the account then completing the schedule. The end anchorage or the dimension in parentheses into the shape codes given inTable 1 and Table 2 shall be used to allow for any permissible deviations resulting from cutting and bending.
Description Tolerance in mm
Cutting of straight lengths (including reinforcement for + 25
Subsequent bending) — 25
Bending < 1 000 +5 up to -5
> 1 000 mm to < 2 000 mm +5 up to -10
> 2 000 mm +5 up to -25

Cutting and bending tolerances

Also, read: Soundness of Cement Test

Radius of Bending in Reinforcement

  • Reinforcement to be formed into a radius exceeding that given in Table 5 shall be supplied straight.
Bar size (mm) 6 8 10 12 16 20 25 32 40
Wire size (mm) 5 6 7 8 9 10 12
Radius (m) 2.4 2.5 2.6 2.8 3.0 3.5 4.3 7.5 14.0 30.0 43.0 58.0

About the author

Krunal Rajput

Hey, I am Krunal Rajput. The Man Behind CivilJungle. I started this site to spread knowledge about Civil/Mechanical/Electrical Engineering. I am a Degree Holder in Civil Engineering.

Add Comment

Click here to post a comment