The right size of rebar cages

When ordering rebar cages , it is important that you order the right one. But how do you know what you need  exactly? To arrive at the right order and assembly, "well begun is half done". Therefore read the drawing carefully and compose the correct reinforcement.

'Reading' the drawing.

Reinforcement drawings are usually drawn in 2D and a number of principles apply:

• The reinforcement is displayed as realistic as possible. Shapes, lengths, lapping lengths lengths and angles are drawn (to scale), as it will appear in practice.
• When links / bars are in the direction in which the sectional drawing is made, they are drawn as a line. The actually cut bars are shown as balls.
• The cut bars are indicated by thin reinforcement marking lines. These lines are extended to the dot, without an arrow or line.
• The link properties are indicated by reinforcement marking lines with an arrow or line.
• All values are displayed in millimeters.

To clarify the above principles an example:

Concrete beam 300 mm x 400 mm
Top reinforcement: 4 x Ø10 mm
Bottom reinforcement: 4 x Ø10 mm
Flank reinforcement: 2 x Ø8 mm
Links: Ø8 mm, placed every 250 mm (measured centre-to-centre).

The width and height of the link is not yet known in connection with the desired coverage. The coverage is shown on the drawing and is often 30 mm or 35 mm.

In the above example, the following specifications apply:

Height: 400 mm - / - 35 mm coverage top - / - 35 mm coverage bottom = 330 mm
Width: 300 mm - / - 35 mm coverage left side - / - 35 mm coverage right side = 230 mm
The overlap in one corner of the link is calculated according to the principle 15 x its own diameter. 15 x 8 mm = 120 mm.

Now that the specifications of the link and reinforcement are known, the correct lengths of the cages and connections can be determined.

Concrete dimensions of the foundation: length 7400 mm, width: 3350 mm, width concrete beam: 300 mm.

The length of the cages on the short sides is 3350 mm - / - 35 mm coverage left - / - 35 mm coverage right = 3280 mm. The standard solution for a corner connection is the following:

The cages on the short sides of the foundation are in this example carried out in Type 2 - Type 2 .

The length of the long side is too long for one cage, this in connection with lifting and transporting. That is why we opt for 2 cages with lapping bars .

The rebar cages are 7400 mm - / - 35 mm coverage left - / - 35 mm coverage right - / - 200 mm 'leeway' / 2 = 3565 mm. By removing 200 mm of the total length of 7400 mm, there is still 'room for maneuver' to easily place and position the cages. Note, never use more than the mutual link distance (in this example 250 mm).

The cages on the long sides are in this example carried out in Type 1 - Type 3 .

In order to connect the cages on the long sides, 1 x 8 lapping bars Ø10 (main reinforcement) and 1 x 2 lapping bars Ø8 (flank reinforcement) are required per connection.

The length for the bars Ø10 = 2 x 655 mm (prescribed lapping length at Ø10 mm) + 250 mm 'leeway' = 1560 mm.

The bars Ø8mm = 2 x 490 mm (prescribed lapping length at Ø8 mm) + 250 mm 'leeway' = 1230 mm.

General tips.

Consider the accessibility of the construction site. When it is difficult to reach, adjust the dimensions of your reinforcement steel order accordingly.

The ends of reinforcing bars are sharp, so use gloves when processing the reinforcing steel.

Do you have any questions or uncertainties about your situation and ordering material? Please contact us.