Structura is a calculation engine, not an assistant. The design code is implemented in plain, deterministic code — the same inputs give the same answer every time, and nothing in the calculation path is generated by a model. That matters for the only test that counts: you have to be able to check the sheet by hand, because you are the one signing it.
1. What you enter
Geometry and loading, in the units a Nigerian office already works in. A slab wants its panel dimensions, thickness, finishes and imposed load; a beam wants its span, section and support condition; a whole-building takedown wants the grid, the storey heights and what sits on each floor.
Concrete grade, steel grade, cover and your preferred bar size are yours to set; the engine works out the arrangement that meets the area required. Defaults are the ones common in Nigerian practice, not the ones that make a section pass.
2. What comes back
A calc sheet, in the order you would have worked it. Every step is one of two things — a line, which states a value and how it was arrived at, or a check, which compares a demand against a capacity and returns PASS or FAIL:
Design moment M M = nL²/8 = 29.88 x 4.00²/8 = 59.76 kNm
K K = M/(bd²fcu) = 0.087
Lever arm z z = d[0.5 + sqrt(0.25 - K/0.9)] = 312 mm
As required As = M/(0.87 fy z) = 478 mm²
Provide 2T20 (628 mm²)
K <= K' = 0.156 0.087 <= 0.156 PASS
Actual span/d 11.4 <= 18.4 PASS
Shortened, but not made up: work those five lines through and they agree. A real sheet carries every intermediate value, the clause it came from, and the assumptions it made.
Failures are loud
A design that does not work says so, and says what to change. It never quietly returns steel that will not do the job, and it never rounds a failure away. Warnings sit at the top of the sheet, not in a footnote.
3. One member, or the whole building
| Run | What it does |
|---|---|
| A single member | Slab, beam, column, footing, stair, lintel, raft or wind, on its own. Free, however many you run. |
| Building takedown | One column line carried from the roof down: slab to beam to column to footing, with loads accumulating storey by storey. |
| Column grid | Every column in the building at once, grouped by the tributary it actually carries — which on a plain grid is the familiar corner, edge and interior families, each with its own sheet. |
Imposed floor loads carried by columns and footings take the BS 6399-1 Table 2 reduction, which you can switch off per design. Slabs and beams are always designed unreduced.
The columns do not have to be a rectangular array
A stairwell where a column would be, an open bay across a living room, an L-shaped footprint, bays of three different widths: the layout is read off the plan and every column is designed where it stands, on half the distance to its nearest neighbour each way. You can fit that layout over the architect's drawing, have the drawing read for you, or type the bay dimensions straight in with no plan on screen at all. See the plan underlay tutorial.
A building may also step in. A column stops at the storey the building stops at, each floor is accumulated against the tributary the storey framing it gives — a storey with fewer columns hands the survivors a larger share — and the bill is counted level by level rather than the ground floor multiplied up. A stepped building is designed for gravity alone, so it caps at three suspended floors; and a column that stops while the floor above still spans over it is a transfer beam, which is refused rather than designed as an ordinary span.
The floor, not a typical member of it
A column grid designs every slab panel between adjacent setting-out lines and every beam span between adjacent standing columns, for each suspended floor and for the roof, with marks — P1, FB.1, RB.1 — that are unique within a level. The typical slab and typical beam are still worked and still shown, because they are the calculation an engineer checks by hand; the typical beam is the worst beam, not an average one.
Two spans, and it is worth not confusing them: a slab panel is measured between setting-out lines, a beam span between columns. Take a column out and the beam over it doubles while the panels either side are untouched, because the beam is still there.
4. Schedules, quantities and drawings
Bar bending schedule
Every member that gets steel gets a schedule to BS 8666 — bar mark, type, size, number, length and shape code. Anchorages and laps use simplified assumptions, which are stated on the sheet and are for you to confirm at detailing.
Bill of quantities
Excavation, blinding, formwork, concrete and reinforcement, as quantities. The rates are yours: prices live in the app's settings, in naira, and are applied at display time. Nothing is priced on our side, so nothing goes stale on our side either.
Drawings
A foundation general arrangement, a column application plan, a layout per floor and a detail sheet per member, exported as DXF for CAD or PDF for the site. Members that would draw identically are folded into one typical sheet that lists the positions it covers — except that a failing member is never folded into a passing typical detail.
The setting-out comes from the layout that was designed, so a pad is drawn under every column there is and nowhere else. A building that steps in gets a column application plan per storey, with the columns that have stopped below drawn dashed and unmarked — a gap where the sheet below shows a column is indistinguishable from one somebody forgot to draw. An unstepped building keeps the single plan it always had.
Report
The whole project as one branded PDF: sheets, schedules, quantities and the disclaimer, in a form you can attach to a submission.
5. Where the work lives
Projects are saved on your device and backed up to your account, so a project designed on a phone opens in the browser. Revising a project, re-running it and re-exporting it are free forever — a credit unlocks a project, not a calculation.
Plan underlays are the exception and deliberately so: an image or PDF you calibrate and measure against never leaves the device, and the engine never sees it. See the privacy policy, and the plan underlay tutorial for how to import, calibrate and map one.
See a sheet for yourself
Structura runs in the browser — nothing to install, and single members are free however many you run.
Open Structura in your browser
On Android, get it on Google Play; on iPhone and iPad, get it on the App Store — same account as the browser.
Read next
- What Structura designs — every member, and the checks each one runs
- What Structura will not do — the exclusions, and why each one is there
- Worked examples — the same calculations done by hand, step by step
- Approval drawings — what a structural submission contains, and where these outputs fit into it