Tutorials DetailCraft help Walkthroughs
Reinforce a rectangular concrete column
A worked example of detailing a rectangular concrete column in DetailCraft: place it, give it longitudinal bars and ties, read the checks, the lap above it and the bar marks, and draw its shop sheet.
Written for DetailCraft 0.9. The same help is inside the app: press F1.
This topic takes one square column from nothing to a checked, drawn and scheduled detail. The general rules for beams, slabs and walls are in Detail reinforced concrete; this is the column's side of it, with numbers you can reproduce.
What a column is here
A rectangular column has a width (along its local x) and a depth across (along its local y), a clear cover to the ties, longitudinal bars on each face and closed ties. Rotating it turns the whole thing; the faces stay "width face" and "depth face".
- The longitudinal bars are given as the number on a width face and the number on a depth face. The corner bars count on both, so 3 and 3 make 8 bars; 4 and 4 make 12.
- The ties are closed rectangles with two hooks at one corner, 135° or 90°. The first tie is a set distance above the floor (and below the next), the end zones have a closer spacing, the middle has a wider one.
- What the bars do at the top: run on and lap with the bars above, turn in with 90° hooks into the floor, or stop under the top.
The worked column
A 400 × 400 mm column, 3600 mm between the floor above and the floor below, #8 longitudinal bars, #3 ties, 40 mm clear cover, f'c 28 MPa, fy 420 MPa, ACI 318-19, interior.
- Open the Concrete tab and set up the grid lines and levels the column stands on (left panel).
- In Add by grid, choose Concrete column, pick the grid intersection and the two levels, set Width (mm) and Depth across (mm) to 400 and choose Add.
- In the Properties panel set:
- Clear cover (mm) 40;
- Longitudinal bars #8, Bars on a width face 3, Bars on a depth face 3;
- Ties #3, Hooks 135°, Spacing between (mm) 300, End zone length (mm) 600, Spacing in the end zones (mm) 150, First one from the face (mm) 50;
- Bars at the top Run on and lap with the bars above.
Each change is one undo step.
What you get
| Part | Result |
|---|---|
| Longitudinal bars | 8 bars #8 (a 3 × 3 ring), each 4375 mm long: the 3600 mm column plus a 775 mm lap above it |
| Lap | 757 mm needed for a compression lap (ACI 318-19 25.5.5.1, fy 420), 775 mm provided: the need rounded up to the next 25 mm |
| Ties | 17 ties #3, each with a cut length of about 1359 mm, spaced 150 mm in the two 600 mm end zones and 300 mm between |
| Steel ratio | 2.5 % of the gross section (limits 1 % to 8 %, ACI 318-19 10.6.1.1) |
| Clear spacing of the bars | 112 mm (needs at least 40 mm, ACI 318-19 25.2.3) |
| Tie spacing | 300 mm (allowed 400 mm: the least of 16 bar diameters, 48 tie diameters and the smaller side, ACI 318-19 25.7.2.1) |
| Tie size | #3 (allowed down to 9.5 mm, ACI 318-19 25.7.2.2) |
All of these are in the element's Checks list; the lap is also in Laps and anchorage.
Cross-ties
With one perimeter tie, only the corner bars are held. ACI 318-19 25.7.2.3 lets a middle bar on a face go without support if it is within 150 mm clear of a corner bar. With 3 bars on a face, as above, that is met. With 4 or more bars on a face it is not, and DetailCraft says so as a warning (Checks and Problems): "cross-ties" are needed. Cross-ties are not drawn yet: add them in the drawing by hand, or choose fewer bars on the face.
For EN 1992-1-1, DetailCraft checks the bar size (at least 8 mm), the number of bars (at least 4), the steel area (0.2 % to 4 % of the section), the clear spacing and the link spacing (9.5.2 and 9.5.3).
The lap, the footing and the column below
- Where a footing of the model stands under the column, the column laps with the footing's starter bars, and their lap is checked too.
- Where another column of the model stands under it, it laps with that column's bars.
- Give your own Lap length (mm, 0 = as needed) to override; one shorter than needed is a problem and is marked * in the table.
- Compression laps are used by default (Compression lap in the settings); choose Tension lap when the column can be in tension.
Marks, schedule and the shop sheet
Identical bars share one mark: the longitudinal bars of the column above are 8C1, its ties 17C2 (the number first, then the kind letter C for column and the running number). They appear in the Bending schedule tab, with the cut length and the weight, and in the CSV from Output › More › Bending.
Choose Shop drawing beside the column for a sheet with the column in elevation (every bar, its mark, the tie zones and the lap dimensioned) and a section at the middle, followed by the bar-bending sheet. Save This sheet as PDF.
What this does not do
- Round columns and spirals, and columns that are not rectangular: not built.
- Corner and cross-ties inside the section, and seismic detailing (ACI 318-19 chapter 18): not built.
- Splices at positions you choose, or staggered: all bars lap at one section.
- Whether the bars are enough for the load: that is the engineer's design.