Hi everyone,
I’m working on a parametric model in Grasshopper (Rhino 8, native components + Kangaroo 2) for a tensile structure covering the grandstands of an athletics stadium. I’ve been struggling with a few geometric issues and would really appreciate some guidance.
The structure covers a semi-circular grandstand (R = 75m, spanning from θ = 15° to θ = 165°, so 150° of arc). The grandstand sits at Z = 8m. The whole system hangs from a single parabolic truss arch (3-chord triangular truss) whose maximum height is around Z = 33m at the crown.
The main constraints are:
- No structural element may obstruct any spectator’s sightline toward the athletics track
- The lowest point of the cable net must remain above 2.33m (clearance)
- The arch must be as light as possible — working by compression/tension, not bending
- The geometry must be fully parametric and controllable via sliders
I have a working Grasshopper script that generates:
1. A parabolic 3D arc curve (using Range → fractions t → z = Z₀ + 4·f·t·(1−t) → Interpolate Curve)
2. A triangular truss along this arc (3 chords: pts_sup, pts_infG, pts_infD, generated by Move from the centroid pts_arc using Unit Z and radial vectors n_hat)
3. A catenary A hanging below the lower chord of the truss (also parabolic)
4. A catenary B at the front of the grandstand, near the track (R = 50m)
5. Radial stay cables from the arch to ground anchors (R = 90m)
Being new to grasshopper I am looking for some help because I can’t get the geometry I want and it’s quite frustrating.
Any help on any of these three problems would be greatly appreciated. I’m happy to share the .ghx file if useful.
Thanks in advance !
Couverture de tribunes de stade - Truss tensile.gh (38.7 KB)
Couverture de tribunes test.3dm (1.1 MB)
