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AutoCAD in Rebar Detailing

Aljosa Vukovic on October 12, 2017

We all know that AutoCAD is the most precise drafting software in the engineering world, especially for 2D drafting.

Civil Engineering, Mechanical Engineering, Electrical Engineering are just some of the many branches that use this incredible software, and Rebar Detailing is one of those departments.

What is Rebar Detailing?

Rebar Detailing is just a small part of the Civil Engineering project, in which it is possible to draw precise reinforcement for concrete walls, beams slabs, columns, and other elements.

AutoCAD is ideal for this kind of drafting because everything is done in units – millimeters, and there must not be a place for error. Length of rebar, minimum hooks, laps, gaps, covers, anchorage, diameters, and other technical parts must be precisely shown on Shop Drawings because engineers and workers will use them on the construction site.

First, architectural and structural plans are provided for the object for work in AutoCAD. The concrete element is then provided with information about its dimensions and what rebar needs to be used for it (cover, diameters, number of layers, anchorage, laps, gaps, and minimum size of hooks for each diameter).

While drawing a concrete beam, if the user needs to start drawing reinforcement, this process should begin from cover. It is important to offset the beam by the thickness of the cover. After that, it is possible to draw the first line using the command Line (which presents the bar) and use the command Array for creating multiple lines that annotate (bars). The command Extend provides the extension of the bar by anchorage, lap, or gap. It’s easy. The same case goes for drafting the beam itself. The command Rec is used for rectangular beams. In the case of a curved beam, it is possible to use the Arc command by specifying the start or center point of the arc – curve of the bar in this case. 

In cases when it is needed to draw the beam on the precise location of the object, the Line command can be used. The process is to use this command and to type the coordinate position when the first point is specified. If stirrups are needed either for beam or column, the main step is to draw the first one, use the Array command, and specify the space between them.

Drawing precise elevation views or sections and other details is crucial in Rebar Detailing, and it was never easier thanks to this software. 

During drafting beams, there are elevation views and sections (in some cases, top view or bottom view if top or bottom bars don’t have the same lengths). When drafting walls, the first step should be drafting of two elevations, in locations near the face and far from the face of the wall. After that, drafting can continue with sections for the side view and top view.

In cases where there are openings in the wall, additional elevation and section for that opening must be placed. The reason for that is if the main wall rebar and additional opening rebar are placed in the same sections, the situation becomes complicated. Now that there are ready elevations and sections ready drafting the wall’s main rebar can begin. It can be done in one, two, three, or more layers, depending on wall thickness and its function in construction.

Situations with external walls and inner walls

External walls are usually supporting structures, and they have a greater thickness and more layers of rebars than internal walls. The same principle is used when drafting one or another. Starting from elevation view, near and far face (they are usually the same), first, horizontal or vertical rebar can be done (depending on the project). After that, the user can apply the Array command.

For side and top views, the same method is valid. In other words, it is possible to draw the first bar and use the Array command. The wall is usually built on another wall or a slab, and that means there are starter bars or couplers which start from the slab or wall below.

Those bars are usually drafted in a grey color. Bars continue by lapping them with those starter bars (or users can continue bars if there are couplers) and Arraying them. All of this is easy. If there is an opening in the wall, things get a bit more complicated.

It is not possible only to use the Array command for bars like in previous examples. These bars need to be stopped before opening. The user should cut the part under and above the opening. In case of bigger openings, bars above and below, it must be anchored into the wall.

The following step is drawing additional bars around openings, horizontal bars, and diagonal bars. This is the reason for having that section and elevation view for additional bars around the opening.

That is why AutoCAD is best for this job. Fast copying of bars, drawing in all that mess is much easier and faster using this software.

Slabs are very similar to walls. First, the user should draw a slab plan and a few sections just to cover all parts. A slab plan is used for drafting top and bottom bars, chair bars, starter bars, and other bars.

Sections are used as details, especially in places where the slab changes its thickness. And again, if there are openings in the slab, then the user must draw additional details for bars that go around that opening.

When there are no openings, the drafting of main layers and other bars is easy because there is only an Array command, just like on wall drawings.

Columns are probably the easiest for work. Rectangular or round columns are pretty easy for drafting. Also, reinforcement is simple for drafting. Drafting vertical bars and stirrups using the Array command is a pretty fast job. Most of the columns are the same, so it is only important to write their number next to the annotation.

So, this was a little tour through drafting reinforcement for concrete elements, but that is not all. It is also essential to draw dimension lines, mark all rebars, and show their shape code. Again, this is not a hard job, thanks to AutoCAD.

The user has to place dimension lines for concrete elements, including their thickness, length, height, cover, and other dimensions. For rebar, the user has to draw dimension lines for their anchorage, lap, and gap.

Their lengths and hooks are not shown because we have shape codes for each bar, making everything more transparent and easier to see.

There are shape codes for every shape of bars. They are placed next to the annotation text. Using the Copy command, this part of drafting can be done very fast. It is only essential to make small changes in the text because each group of bars has its bar mark when they are the same.

This is just a short explanation of how Rebar Detailing works using AutoCAD software, mostly for cast-in-situ elements. There will be more articles on this topic and in the meantime, feel free to read our blog about Precast Concrete Elements.

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