Slab reinforcement drawing from a DXF background

Not every project starts with a 3D model. If you have a floor plan in a DXF file, you can prepare the reinforcement drawing of a slab in IgentDraw without working in IgentForm. This tutorial shows the whole way: from importing the background, through reinforcement regions, openings and bar laps, to a DXF file ready to be opened in a CAD program.

The most important thing, however, is what happens along the way: the drawing is not drawn but generated from parameters. Why this makes such a big difference is explained in the last part of the tutorial. The video and the screenshots come from the Polish version of the program — IgentDraw is also available in English and French.

Step 1. Importing the DXF background

You start by loading a DXF file with the plan of the slab. In the import window you:

• choose the layers to be loaded,
• set the drawing units,
• indicate the storey on which the background will be placed.

The DXF file should be saved in the V12 format — this is the format in which the program imports and exports drawings.

The slab contour can have any shape and can contain openings. The program can also recognize contours from a selected layer automatically.

The slab contour with an opening after import from the DXF file.

Step 2. Reinforcement regions

On the basis of the contour you define reinforcement regions. A region can be, among others, a slab, an opening, a ring beam, a shaft or a slab thickening. For a slab you give the thickness and the material.

In the example three regions are created:

• base mesh — covers the whole slab,
• opening — with its own reinforcement around the edges,
• additional reinforcement — a rectangular region with extra bars.

Regions can be indicated with snap points or with lines from the DXF background.

Step 3. Reinforcement parameters — the drawing creates itself

Every region has its own reinforcement parameters. For a slab these include:

• the reinforcement type (bottom or top),
• the bar diameter and spacing — separately in the X and Y directions,
• the bar shape, for example a straight bar or a bar with hooks at the ends,
• the bottom and side cover,
• the reinforcement angle and the division of bars into zones.

When the reinforcement is switched on, the program immediately generates the drawing with descriptions, the summary reinforcement table and the 3D reinforcement. After any parameter is changed — diameter, spacing or bar shape — all three are generated again.

The reinforcement drawing generated for the whole slab. On the left, the parameters of the region: reinforcement type, diameters, spacings and covers.

3D reinforcement of the same slab — the bars are cut to the contour and to the opening.

Step 4. Openings and edge reinforcement

The program cuts the bars at openings by itself. An opening is at the same time a separate reinforcement region in which you define the reinforcement around the edges: bars parallel to the edges and diagonal bars at the corners, top and bottom, with their diameter, spacing, number and length beyond the edge of the opening.

The position of the opening is a parameter. When you change its coordinates, the drawing is generated anew — with the bars cut to the new position of the opening.

Reinforcement of an opening: bars parallel to the edges and diagonal bars at the corners.

Step 5. Bar lengths and laps

In the reinforcement options you set the code, the steel grade, the maximum and minimum bar length and the lap length. Bars longer than the maximum length are divided automatically, with laps taken into account. The position of the laps can be shifted.

Division of bars with laps. On the left, the reinforcement options: maximum bar length, lap length and lap shift.

Step 6. Summary reinforcement table

The reinforcement table is created together with the drawing and always corresponds to what is on the drawing. It contains the bar marks together with their shapes.

The summary reinforcement table generated automatically.

Step 7. Descriptions

The program places the bar descriptions by itself. When they clash with each other or with the drawing, you move them manually. For legibility, the bars can also be distinguished by colors according to their diameters.

Bar descriptions after manual correction of their position.

Step 8. Export to DXF

You save the finished drawing in DXF format (V12) and load it into your CAD program, for example AutoCAD or ZWCAD. The reinforcement, descriptions, dimension lines and the table go to separate layers, which makes the final touches easier.

The reinforcement drawing and the table after the DXF file is opened in a CAD drawing viewer.

Parametric work versus traditional drawing

This is the most important part of this tutorial. In traditional reinforcement drawing every change to the design means manual corrections in several places at once. In parametric work you change one value and the program does the rest.

Change in the design	Traditional drawing	Parametric work in IgentDraw
An opening is moved	Manual cutting of bars, redrawing the reinforcement of the opening, correcting the descriptions and the schedule	Change the coordinates of the opening — the bars are cut again
A different diameter or spacing	Redrawing the bars, correcting the descriptions and recalculating the schedule	Change one parameter of the region
A different bar shape, e.g. with hooks	Redrawing the bars and correcting the lengths in the schedule	Choose a different bar shape
A different lap length	Dividing the bars again on the whole drawing	Change one reinforcement option

The decisive advantage of parametric work: a change to the design does not mean drawing again. The drawing, the summary reinforcement table and the 3D model are created from the same parameters, so after every change they stay consistent with each other.

In practice this gives three benefits:

1. Speed of changes. A correction that in traditional drawing requires redrawing a part of the documentation comes down to changing a parameter here.
2. Consistency of the documentation. The reinforcement table cannot drift apart from the drawing, because both are created from the same model.
3. Control in 3D. The 3D reinforcement is available all the time, so the arrangement of bars can be checked before the drawing is issued.

What next

• Are you designing a whole building? See how to reinforce slabs, beams, columns and walls on the basis of a model from IgentForm: Reinforcement drawings of a reinforced concrete building.
• Would you like to try this on your own floor plan? Download the IgentDraw demo version — it works with full functionality for 30 days.