Introduction to Rebar Detailing
Rebar Detailing is a detailed construction engineering process, usually done by the Rebar fabricators, structural engineering consultants or the contractors to prepare a Rebar placing drawing and a Bar Bending Schedule. Qualified and experienced Rebar Detailers are required to do Rebar Detailing. A Rebar Detailing software like RGS REBAR or VISKAR BIM is also required to complete this job with quality and promptly.
Rebar Detailing is called in different names like Rebar scheduling, RC Detailing and Bar Bending schedule predation, RC Drafting, etc in various countries.
Bar Bending schedule is a significant headache in every construction project. Many construction project managers think that Bar Bending schedule preparation can be done in the site. They also want to use Excel sheets or hand calculations in a paper. Bar Bending schedule is too expensive to use all such primitive methods for preparation. This happens mainly because, in many countries, Rebar Placing drawing preparation is not in practice and hence the Proper way to prepare a Bar Bending schedule is not known to them.
I request the readers to understand why Rebar detailing is a mandatory process in many countries and what are the accrued benefits. To reiterate, If your company is not preparing Rebar placing drawings, you are wasting a lot of Rebar and the quality of your structure is questionable. I am only trying to emphasize the importance.
What is the purpose of doing Rebar Detailing?
The main objectives of doing 2D Rebar detailing are as follows:
a) To Prepare an error-free Bar bending schedule, when fabricated should fit in the concrete formwork without any issue. The same Bar Bending Schedule will be used for accounting and invoicing.
b) To prepare a detailed Rebar placing drawing (Erroneously called as Rebar Shop drawings). This Rebar placing drawing guides an Ironworker in such a way that the Rebar can be placed correctly in the site without any issues.
c) To let the structural engineer, verify and approve if the structural design intent is properly converted into the Rebar Placing drawings and Bar bending schedules.
d) To do a Rebar wastage analytics and reduce potential scrap existing in the Drawing level.
What are the skill sets required to do Rebar Detailing?
Rebar detailing is a meticulous and involved job that will have a significant impact on the construction. To do Rebar detailing the following skills are required.
1. To read the structural drawings and understand how an engineer intent to construct the structure with various structural elements like Footings, Slabs, walls, Beams, staircases etc. For doing Infrastructure projects a knowledge on Pile caps, piers, segments, Abutment walls, phylon’s etc are needed.
2. To read and understand the notes, Schedules and other information that are relevant for Rebar detailing of the various elements.
3. To read the construction drawings from other trades like Architectural and MEP to check the consistency, clash and any other ambiguities that will affect Rebar detailing.
4. To raise a Request for Information (RFI) to the Relevant stakeholder and get replies for the missing info, ambiguous situations, conflicts etc.
5. To have a fundamental understanding of how various structural elements are reinforced. For example, we will take a BEAM
- What are the dimensions of the Beams and the supports?
- What will be the General cover to be followed on Top, Bottom and side faces of the Beam?
- Are there any complications in the element like Steps, Size variations between continuous beams, Depth variations etc.,? The detailer has to check for the existence of such complications and provide proper detailing.
- What is the various Rebar in a Typical continuous Beam?
Where you can Lap Top and Bottom Bars? Where you cannot Lap? (This is a Basic knowledge that a detailer must possess. He should be aware of the Stress and compression zones and at least should know how to draw a Bending moment diagram. These basics will help in the long run)
- What would be the Lap length to be followed? Is it from the code (ACI defines Class A class B Tension/compression Laps etc) or is it provided by the structural engineer in the structural drawing?
- What are the Bar supports and other accessories to be provided? / How to calculate their quantities?
- Generally, where will the congestion of Rebar occur? (In beams the column- Beam junction.) How to resolve these congestion issues?
- Will the Element be poured separately or with any other element? In that case is there any Dowels(Startup Bars in Middle East language) required to be provided?
- Is any Rebar needs to be provided with special treatments like Epoxy coating, End Threads for couplers etc?
6. To have a strong Rebar detailing knowledge
- What is the detailing code to be used?
- What are the different standard Bend Shapes defined in the code?
- What is the Pin Diameter recommended by the Code?
- What are the standard Hook lengths for different angles?
- What are the lap lengths to be used?
- How to calculate development lengths?
- What is the Cut length calculation to be followed?
- How to Calculate Bar sizes and quantity from the Areas of Steel provided by the structural engineer. This skillset is required when you work for U.K projects and in many countries, this knowledge is required to choose alternate Bar sizes, based on site requirement. Please note that the structural engineers should approve the alternate Bar sizes.
7. To have a proper understanding of the Rebar Fabrication process (Cutting & Bending)?
- What are the Different Bar sizes available?
- What would be the regular stock lengths that are readily available to fabricate?
- Is Rebar Bent in Shop or Site?
- Do they use CNC machines or not?
- What would be the preferred format for Bar bending schedule?
- If CNC Bar list is required, what is the format required?
- What are the length limitations in shipping L Bars and Arc Bars etc?
- What would the maximum shipping length?
- What will be maximum Truckload allowed to Transport Rebar?
8. To have a proper understanding of the Rebar Placing drawing presentation style to suit the Contractors Placing crew.
- The Placing drawings are prepared in different ways.
- The detailer should know the expectations of the client and prepare Rebar Placing drawings in that format.
- It's also better to know the approval process for the Rebar Detailing and Rebar placing drawings.
9. To do Rebar Detailing using a 2D Rebar detailing software like RGS REBAR or a 3D Rebar Detailing software like VISKAR BIM
- The Rebar detailer should first know How to manually detail Rebar using Paper and pencil. The basics must be understood. This should be done before even learning any software.
- Doing Rebar detailing in an Excel sheet or a piece of paper is undoubtfully a wrong approach. I will explain separately on how this leads to Rebar wastage in the site and how the Structures Quality is devastated due to lack of professional practices.
- Rebar detailing with plain CAD software will be laborious, error-prone and usually end up in a big Mess.
I am planning to share the knowledge I have gathered in the past 20 years in Rebar Detailing in this blog. I am also going to share a Rebar detailers self-learning Training program. Starting from Rebar detailing to 3D Virtual Construction of Concrete structures, a lot of knowledge is going to be shared in this Blog. The world is going to be needing more Rebar detailers in the future.