Handling Complex Geometry – Ribbon

Recently, we were awarded a project to detail a curved section on the bridge for a reputed organization in Australia. The geometry involved presented some unique challenges.

From the elevation, the structure followed a non-linear zig-zag curvature, creating a dynamic and aesthetically driven form.

In the section view, the shape appeared triangular, with the designer providing set-out points at the bottom of the triangle.These bottom curves were designed to be tangent continuous lines.

Practical Fabrication Limitations

Before proceeding with modelling, it’s important to understand a key fabrication constraint:

• Only cylindrical and conical sections can be rolled.
• These shapes allow for proper flat pattern development.

While modeling software allows us to create any shape, real-world fabrication has limitations that must be respected.

We need to get the tangent continuous lines to get smooth transition of curves.

The Core Issue

When we followed the design set-out points exactly and developed the geometry on a conical surface, we observed the following:

• The bottom curves remained tangent continuous, as intended by the designer.
• However, the top curve (apex) lost its tangent continuity.

This created a visual inconsistency, especially since the top curve plays a key role in the overall aesthetics of the structure.

Since the project had a strong architectural and aesthetic requirement, maintaining smooth curves at the top was critical. To resolve this, we proposed:

• Adjusting the set-out dimensions without changing the original curve radii
• Introducing transition lines to connect areas where tangent continuity was breaking
• Refining the geometry to achieve smooth, continuous curves at the apex.

This ensured that both the bottom and top curves maintained visual continuity, while still staying within fabrication limits

In such projects, detailers must balance geometry, fabrication feasibility, and aesthetics. Careful adjustments can ensure both practical execution and the intended visual outcome are achieved.