BOXCULVERT generates the whole detail for a cast-in-place reinforced concrete box. From thirteen numbers you get a complete, dimensioned sheet.
What BoxCulvert does
Sectional plan through the walls, dimensioned inside and out. Roof plan of the slab over. Section 1 through the side walls, with reinforcement and dowels. Section 2 through the end walls, likewise. And pipe connections on any of the four sides, set out from their inverts.
How to use it
- Load the routine with
APPLOAD, or put it on your support file search path. - Type
BOXCULVERT. - Pick the point to draw at.
- Give the thirteen dimensions, in feet — see below.
- Add pipe connections on any side, set out from their inverts.
How it works
It is self-contained. The routine this was rebuilt from inserted three blocks from hard-coded paths — a wall shear key, a slab key and a reinforced concrete pipe, all under /acad/strblk/. None of those blocks exist any more, so it could not complete a single culvert without erroring at the first key. All three are now drawn as geometry from dimensions already to hand. Nothing has to be installed and nothing can go missing.
The two sections are one function called twice. Section 1 cuts the long way and Section 2 the short way, but a box culvert is symmetrical — both are the same drawing with a different clear span and a different pair of dowel lengths. They were two near-identical 200-line blocks. As one function, the reinforcement cannot drift between them, which is exactly the sort of discrepancy that reaches site.
It draws where you pick. The original always drew at 10,5 regardless, so a second culvert landed on top of the first.
Notes and limits
- Dimensions are entered and drawn in FEET, and dimension text is written in inches — the value times twelve — which is how culvert sheets are annotated in imperial practice.
- Cover and bar offsets are decimal-foot constants in the file: 0.16 ft is about 2 inches, 0.08 ft about 1. Edit them there if your cover differs.
- This is imperial. A metric job needs the constants and the text conversion changed together.
- One undo group covers the whole detail.
Download and details
| Name | BoxCulvert — a complete reinforced concrete box culvert detail |
| Download | BoxCulvert.lsp — 23.3 KB, plain AutoLISP source. Downloads directly; no zip to unpack. |
| Type | AutoCAD AutoLISP routine |
| Command | BOXCULVERT |
| Requires | nothing beyond a CAD platform with AutoLISP. |
| Source size | 23.3 KB, 511 lines |
| Error handling | Yes — a *error* handler restores every system variable it changed, on cancel as well as on error. |
| Undo | The whole operation is wrapped in a single undo group, so one U reverses all of it. |
| Compatibility | AutoCAD (any release with AutoLISP), BricsCAD, ZWCAD, GstarCAD, ProgeCAD and other IntelliCAD-based platforms. AutoCAD LT needs a LISP enabler. No .NET, no ObjectARX, no installer. |
| Author | YZ, August 2026 |
| Licence | Free to use, supplied “as is” with no warranty. |
References
- Concrete reinforcing tips — detailing conventions for reinforcement
- Dimensioning to standards — the conventions the dimensions follow
- More free AutoLISP routines on this site
- Wisey’s Steel Shapes — free structural steel section drawing program