# Hollow section (EN 10219-2 SHS / RHS)

Cold-formed welded structural square (SHS) and rectangular (RHS) hollow sections at any size, wall and length; and
sharp-cornered light tubes (`corners = "sharp"`), the catalogue's generic square and rectangular tubes.

## Geometry

Outside width **B** (`width`) along X, outside height **H** (`height`) along Y, wall thickness **T** (`wall`),
centred on the origin and extruded along +Z by `length`. The corners are rounded with the outside radius ro and the
inside radius ri that EN 10219-2 uses to calculate the sectional properties of its tables:

| Wall T | ro | ri |
|---|---|---|
| T ≤ 6 mm | 2.0 T | 1.0 T |
| 6 mm < T ≤ 10 mm | 2.5 T | 1.5 T |
| T > 10 mm | 3.0 T | 2.0 T |

so the section area and mass agree with the tables. (Real corner profiles vary within the standard's tolerance:
1.6 T to 2.4 T outside for T ≤ 6 mm, 2.0 T to 3.0 T for 6 < T ≤ 10 mm, 2.4 T to 3.6 T above.) With `corners =
"sharp"` the corners are square inside and out.

## Parameters

| Parameter | Meaning |
|---|---|
| `width` | Outside width B, mm |
| `height` | Outside height H, mm (equal to B for a square section) |
| `wall` | Wall thickness T, mm |
| `length` | Length, mm |
| `material` | `steel-s355` (S355J2H), `steel-s235` (S235JRH), EN 10219-1; `stainless-304` (1.4301); or `unspecified` (no material assigned) |
| `corners` | `en-10219` (the radii above) or `sharp` |

## Source

EN 10219-2:2006, *Cold formed welded structural hollow sections of non-alloy and fine grain steels — Part 2:
Tolerances, dimensions and sectional properties*, read from a full copy of BS EN 10219-2:2006 (<https://icdn.tradew.com/file/201801/1572618/pdf/6800507.pdf>):

- corner radii for the sectional properties: Annex B, clause B.3 (printed p. 21): outside ro = 2.0T / 2.5T / 3.0T and
  inside ri = 1.0T / 1.5T / 2.0T for T ≤ 6, 6 < T ≤ 10 and T > 10 mm;
- tolerance on the external corner profile: Table 3 (1.6T to 2.4T, 2.0T to 3.0T, 2.4T to 3.6T); the same in the 2019
  edition's Table 3 (SIST EN 10219-2:2019 preview, <https://cdn.standards.iteh.ai/samples/38063/99682514fcf94faabd079f41b1a7854e/SIST-EN-10219-2-2019.pdf>);
- sizes B × H × T: Table C.2 (square) and Table C.3 (rectangular); every preset is a row of these tables.

The radii rule is cross-checked by Roymech's cold-formed SHS / RHS tables (<https://roymech.org/Useful_Tables/Sections/SHS_cf.html>,
<https://roymech.org/Useful_Tables/Sections/RHS_cf.html>). EN 10219-2 was revised in 2019 (formulae then in Annex A,
tables in Annex B); its radii text was not available, so the edition matched is 2006.

Generic square tubes of the catalogue (side and piece length only) become presets only where EN 10219-2 lists the
section their own reference model has: 25 × 25 × 2 (EN 10219-2:2006 Table C.2; copy consulted:
https://icdn.tradew.com/file/201801/1572618/pdf/6800507.pdf, page 29), at the entry's length. Their other sizes
(10 × 1, 15 × 1.2, 20 × 1.6, 30 × 2.4, 40 × 3.2) are not EN 10219-2 sections: they are sharp-cornered presets
measured from their own models (below).

## Sources: generic light tubes

No standard covers the catalogue's generic light tubes (their walls are in neither EN 10219-2 nor EN 10305-5).
**Their geometry was measured from the published reference models** below: each model's mid-length section (outside
extents, inside extents; wall = the difference / 2; all corners square) and is checked preset by preset against its
own model (bounding box within 0.05 mm, 0.5 % over 100 mm, and volume within 2 %). Their models name no material, so
these presets have `material = "unspecified"`.

| Tube | Wall | | Tube | Wall |
|---|---|---|---|---|
| 10 × 10 | 1.0 | | 20 × 10 | 1.0 |
| 15 × 15 | 1.2 | | 30 × 15 | 1.2 |
| 20 × 20 | 1.6 | | 40 × 20 | 1.6 |
| 30 × 30 | 2.4 | | 60 × 30 | 2.4 |
| 40 × 40 | 3.2 | | | |

- **step.parts**, `square_tube_side<s>_l<length>` and `rectangular_tube_size<w>x<h>_l<length>`
  (https://www.step.parts, repository https://github.com/earthtojake/step.parts, commit c6113328, `catalog/step/`):
  step.parts' own "analytic simplified" models, original project material under the repository's **MIT** licence
  (© 2026 earthtojake).

Simplifications (the models'): square corners, no weld seam.

Preset list: sizes of the step.parts catalogue (MIT), see `library/NOTICE.md`; EN 10219 presets are 1000 mm long,
generic ones have the catalogue's length.