Need help creating a parametric post-tension cable with Dynamo for Revit

[soufianeoubekhan1]

Hello everyone,

I’m looking for some guidance and would really appreciate any help from the Dynamo/Revit community.

I’m developing a Dynamo script for Revit to automatically generate a parametric post-tension cable.

The goal is for the user to define:

• The cable diameter.
• The cable length.
• The deviation points (X, Y, Z coordinates).

The script should then automatically generate:

• A 3D cable path (curve).
• The corresponding 3D solid cable.

Ideally, I would also like the solution to be flexible enough to allow adding or removing deviation points easily.

If anyone has experience with this type of workflow (Dynamo, Python, or the Revit API), or knows of similar examples or resources, I would really appreciate your help.

Thank you in advance!

[sovitek]

Hello @soufianeoubekhan1 and welcome to the community yeah should be possible, try show us what you have tried so far, and we can help from there…and if you could share a small rvt sample we can try on, you will even have better luck

How to get help on the Dynamo forums

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[RMohareb]

@soufianeoubekhan1 may be that help you

bridge Bim model BrIM | Ramiz mohareb | 16 comments

Bridge BIM post tension cable prestress Dynamo revit

prestress cable BIM modeling for box bridge by using Revit civil3d and Dynamo

[Shara_Howard]

This sounds like an interesting Dynamo project. Sharing your current graph or Python script and a sample Revit file will make it much easier for others to suggest the right approach.

[sovitek]

Yeps @Shara_Howard and welcome to the forum…pretty easy, and right the forum isnt a place for order finish solutions from other without nothing ;), as will not help anyone…but for sure its an interesting Dynamo project…

[soufianeoubekhan1]

Thank you!

At the moment, I’m only trying to build a proof of concept for one single post-tension cable, not the entire slab.

My first idea was to create an adaptive family. It works, but I quickly ran into a limitation: I have to manually place every adaptive point and manually enter the eccentricity (Z offset) for each one. For a single cable that’s acceptable, but for hundreds of cables it becomes extremely time-consuming.

That’s why I started thinking about a Dynamo workflow instead.

The idea would be to provide the cable path together with the deviation points and their eccentricities, and let Dynamo automatically generate the complete 3D cable.

If I can make this work for one cable, I can then apply the same workflow to all the post-tension cables in the slab.

[soufianeoubekhan1]

Thank you, Mr. Ramiz, for sharing this. I really appreciate your help

[jacob.small]

I recommend you look into having Dynamo place the adaptive family instead of generating the geometry.

[RMohareb]

@soufianeoubekhan1

The idea would be to provide the cable path together with the deviation points and their eccentricities, and let Dynamo automatically generate the complete 3D cable.

If you already have the cable path points, using a Duct element is generally a better approach than using an Adaptive Family, as a duct can be generated from a path with a variable number of points. However, this approach is only valid if the cable path points are based on the actual BIM geometry.

In practice, the cable path points exported from the FEM software are typically generated from a simplified analytical model, not from the detailed BIM geometry. The differences arise because the FEM model uses simplified geometry and simplified reference datums to define the cable profile. As a result, directly importing these cable points into the BIM model will often produce a cable that does not match the real structure.

To overcome this issue, the BIM workflow should replicate the same procedure used in the FEM software instead of importing the cable points directly:

1. Define the cable reference datum (the reference path or axis used to define the cable in the BIM model).

2. Locate the cable control points on this BIM datum, corresponding to the control points used in the FEM model.

3. Apply the same cable-fitting equation or algorithm used by the FEM software to generate the cable profile based on these control points.

4. This produces a new set of cable path points that accurately follows the real BIM geometry rather than the simplified FEM model.

5. Finally, use these generated points to create the cable in the BIM model. For this step, I recommend using a Duct element instead of an Adaptive Family, as it can be created from a path with a variable number of points and is therefore more flexible for cables with different geometries.

Befor you start you need to understand how the cable defined in the FEM you will undarstand what mean datum, control point and fit the cable then think how to import it in bim model .

this reference will help you https://www.fhwa.dot.gov/bridge/concrete/hif15016.pdf

PP 75