BS 8666 Shape Codes: Best Practices and Tips for Rebar Scheduling and Bending
BS 8666 Shape Codes: A Guide for Rebar Scheduling and Bending
If you are involved in the design, fabrication or installation of steel reinforcement for concrete structures, you need to be familiar with BS 8666 shape codes. These are a set of standardised symbols and formulas that specify the dimensions, angles and bends of reinforcing bars. They are essential for ensuring that the rebar conforms to the design specifications and meets the structural performance requirements.
bs 8666 shape codes pdf download
In this article, we will explain what BS 8666 shape codes are, how they work, and how to use them effectively. We will also highlight the main changes in the latest update of BS 8666:2020, which aligns the standard more closely with BS EN 1992-1-1 (Eurocode 2). Finally, we will discuss the benefits and challenges of using shape codes, and provide some useful tips and resources for rebar scheduling and bending.
Shape codes overview
Shape codes are a way of representing the geometry of reinforcing bars using numbers, letters and symbols. They are used to communicate the required shape and dimensions of rebar between designers, fabricators and installers. They also help to avoid confusion, errors and disputes that may arise from using different terminology or units.
Each shape code consists of two parts: a number that indicates the type of shape, and a letter that indicates the grade of steel. For example, shape code 12C means a bar with two bends in opposite directions (shape code 12) made of grade B500B or B500C steel (letter C).
The shape code is followed by a series of values that specify the length and angle of each segment or bend of the bar. These values are based on standard formulas that take into account the radius, diameter and projection of the bends. For example, shape code 12C A=1000 B=500 C=135 means a bar with two bends in opposite directions (shape code 12) made of grade B500B or B500C steel (letter C) with a length of A=1000 mm between the end and the first bend, a length of B=500 mm between the two bends, and an angle of C=135 degrees between the two segments.
The following table shows a list of shape codes with diagrams and formulas according to BS 8666:2020. The table also shows the minimum values for A, B, C, D and E for each shape code.
Shape code
Diagram
Formula
Minimum values
00
L=A
A ≥ P
01
L=A
A ≥ P
11
L=A + (B) - 0.5r - d
A ≥ P, B ≥ P
12
L=A + (B) - 0.43R - 1.2d
A ≥ (R + d) + max(5d, 90), B ≥ (R + d) + max(5d, 90)
13
L=A + 0.57B + (C) - 1.6d
A ≥ P, B ≥ (R + d) + max(5d, 90), C ≥ P
14
L=A + (C) - 4d
A ≥ P, C ≥ P
15
L=A + (C)
A ≥ P, C ≥ P
63
L=2A + B + 2(C) - 4d
A ≥ P, B ≥ P, C ≥ P
Scheduling and bending requirements
Besides using shape codes, rebar scheduling and bending also need to follow some other requirements and specifications according to BS 8666:2020. These include the minimum radius, former diameter and end projection for each shape code, as well as the tolerances and deviations for bending dimensions and angles.
The minimum radius, former diameter and end projection are the values that ensure that the rebar can be bent without cracking or losing strength. The radius is the distance from the center of the bend to the center of the bar. The former diameter is the diameter of the tool or machine that is used to bend the bar. The end projection is the distance from the end of the bar to the start of the bend.
The following table shows the minimum values for radius, former diameter and end projection for each nominal size of bar and type of steel according to BS 8666:2020.
Nominal size of bar, d. mm
Minimum radius for scheduling, r. mm
Minimum diameter of bending former, M. mm
Minimum end projection, P General (min 5d straight), including links where bend 150º mm
Minimum end projection, P Links where bend 150º (min 10d straight) mm
6
12
24
110a
110a
8
Scheduling and bending requirements
Besides using shape codes, rebar scheduling and bending also need to follow some other requirements and specifications according to BS 8666:2020. These include the minimum radius, former diameter and end projection for each shape code, as well as the tolerances and deviations for bending dimensions and angles.
The minimum radius, former diameter and end projection are the values that ensure that the rebar can be bent without cracking or losing strength. The radius is the distance from the center of the bend to the center of the bar. The former diameter is the diameter of the tool or machine that is used to bend the bar. The end projection is the distance from the end of the bar to the start of the bend.
The following table shows the minimum values for radius, former diameter and end projection for each nominal size of bar and type of steel according to BS 8666:2020.
Nominal size of bar, d. mm
Minimum radius for scheduling, r. mm
Minimum diameter of bending former, M. mm
Minimum end projection, P General (min 5d straight), including links where bend 150º mm
Minimum end projection, P Links where bend 150º (min 10d straight) mm
6
12
24
110a
110a
8
16
32
115a
115a
10
20
40
120a
130
12
24
48
125a
160
50
175
350
475
725
a The minimum end projections for smaller bars is governed by the practicalities of bending bars.
NOTE 1: Due to "spring back" the actual radius of bend will be slightly greater than half the diameter of former.
NOTE 2: BS 4449:2005 grade B500A in sizes below 8 mm does not conform to BS EN 1992-1.1:2004.
Source: BSI British Standard documentation
The tolerances and deviations are the allowable variations from the specified dimensions and angles of rebar bending. They are necessary to account for the inevitable errors and uncertainties that may occur during fabrication and installation. They also help to ensure that the rebar fits within the concrete cover and does not interfere with other reinforcement or embedded items.
The following table shows the tolerances for cutting and/or bending dimensions according to BS 8666:2020. They shall be taken into account when completing the schedule. The end anchorage or the dimension in parenthesis in the shape codes specified on Typical Bend Shapes shall be used to allow for any permissible deviations resulting from cutting and bending.
Cutting and Bending Processes
Tolerance (mm)
Cutting of straight lengths (including reinforcement for subsequent bending)
+25, -25
Bending: 1000mm
+5, -5
Bending: > 1000mm to 2000mm
+5, -10
Bending: > 2000mm
+5, -25
Length of Bar in Fabric:
+25, -25, or 0.5% of the length (whichever is greater)
Tolerances for shape code 01, stock lengths, shall be subject to the relevant product standard, e.g. BS 4449:2005.
Source: BSI British Standard documentation
The following table shows the tolerances for bending angles according to BS 8666:2020. They shall be taken into account when completing the schedule. The tolerances apply to each individual bend and not to the total angle of a series of bends.
Nominal size of bar, d. mm
Tolerance on bending angles (degrees)
16
2
> 16
3
Benefits and challenges of using shape codes
Using shape codes for rebar scheduling and bending has many benefits for the construction industry. Some of the main benefits are:
Shape codes improve the efficiency, accuracy and quality of rebar fabrication and installation. They reduce the need for manual measurements, calculations and drawings, and ensure that the rebar conforms to the design specifications and meets the structural performance requirements.
Shape codes reduce waste, errors and costs. They minimise the amount of rebar that is cut off or discarded, and avoid the need for rework or correction of mistakes. They also save time and labour costs by simplifying the communication and coordination between designers, fabricators and installers.
Shape codes enable more complex and innovative designs. They allow for more flexibility and creativity in designing rebar shapes and configurations that suit different structural needs and aesthetic preferences. They also facilitate the use of advanced technologies such as 3D printing and 4D printing for rebar fabrication.
However, using shape codes also poses some challenges and difficulties for the construction industry. Some of the main challenges are:
Shape codes require training and education. They are not intuitive or easy to understand for everyone, especially for those who are not familiar with the standard or have limited literacy or numeracy skills. They also require constant updating and revision to keep up with the changes in the standard and the technology.
Shape codes depend on the availability and quality of tools and machines. They require specialised equipment and software for rebar cutting, bending and verification. These tools and machines may not be accessible or affordable for everyone, especially for small-scale or remote projects. They may also malfunction or break down, causing delays or errors.
Shape codes may not cover all situations or scenarios. They are based on general principles and assumptions that may not apply to every case or context. They may not account for all the factors or variables that affect rebar bending, such as temperature, humidity, corrosion, fatigue, etc. They may also not accommodate all the preferences or requests of clients or stakeholders.
Conclusion
In conclusion, BS 8666 shape codes are a useful and important tool for rebar scheduling and bending. They help to ensure that the rebar conforms to the design specifications and meets the structural performance requirements. They also help to improve the efficiency, accuracy and quality of rebar fabrication and installation, as well as to reduce waste, errors and costs. However, using shape codes also poses some challenges and difficulties that need to be overcome. These include the need for training and education, the availability and quality of tools and machines, and the coverage and applicability of shape codes for different situations and scenarios.
Therefore, we recommend that anyone who is involved in the design, fabrication or installation of steel reinforcement for concrete structures should be familiar with BS 8666 shape codes and how to use them effectively. We also suggest that they should keep up to date with the latest changes and developments in the standard and the technology. Furthermore, we encourage them to explore more complex and innovative designs that can be achieved with shape codes and advanced technologies such as 3D printing and 4D printing.
If you want to learn more about BS 8666 shape codes and how to use them for rebar scheduling and bending, you can download a free PDF guide from our website or contact us for more information. We are happy to help you with any questions or queries you may have.
FAQs
Here are some frequently asked questions about BS 8666 shape codes and their answers.
What is the difference between BS 8666 and BS EN 1992-1-1 (Eurocode 2)?
BS 8666 is a British Standard that specifies the requirements for scheduling, dimensioning, bending and cutting of steel reinforcement for concrete structures. It is based on BS EN 1992-1-1 (Eurocode 2), which is a European Standard that provides the general rules and principles for the design of concrete structures. BS 8666 aligns the shape codes and notation with BS EN 1992-1-1, but also provides some additional guidance and specifications that are specific to the UK context.
How to convert between different shape codes from different standards?
Different standards may use different shape codes or notation for rebar scheduling and bending. For example, ASTM A497 uses letters instead of numbers for shape codes, while ISO 3766 uses a different set of symbols and formulas. To convert between different shape codes from different standards, you need to refer to the relevant standard documents or use online tools or apps that can perform the conversion automatically.
How to check the compliance and quality of rebar bending?
To check the compliance and quality of rebar bending, you need to verify that the rebar meets the specified dimensions, angles and tolerances according to the schedule and the standard. You can use various methods and tools to measure and inspect the rebar bending, such as rulers, protractors, gauges, calipers, scanners or cameras. You can also use software or apps that can analyse the rebar bending data and generate reports or feedback.
How to use software tools or apps for rebar scheduling and bending?
There are various software tools or apps that can help you with rebar scheduling and bending. Some of them can help you create or edit rebar schedules using shape codes and notation. Some of them can help you calculate or simulate rebar bending using formulas or models. Some of them can help you verify or optimise rebar bending using measurements or analysis. You can choose the software tools or apps that suit your needs and preferences.
Where to find more resources and guidance on shape codes?
If you want to find more resources and guidance on shape codes, you can visit our website or contact us for more information. We have a range of resources available for download or purchase, such as PDF guides, books, videos or courses. We also offer consultancy and training services on rebar scheduling and bending using shape codes. We are happy to help you with any questions or queries you may have.
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