I was recently invited to the city of Changsha, China to conduct a 2 week workshop with Architecture students from Hunan University and also build a pavilion within certain cost/size/material/fabrication/time constraints. We were 3 tutors: Yu Du (Zaha Hadid Beijing), Shuojoing Zhang (UN Studio Shanghai) and myself, along with support from the Hunan University staff. This post is a documentation of what we built and how we got there.
The design brief was to design a pavilion outside the main DAL (Digital Architecture Lab) studio space with some seating within volume constrains of 6m x 3m x 3m, but mostly act as a sculptural piece that demonstrates a parametric design-to-fabrication process. The form we came up with was a single sculputral doubly curved surface that formed seating and a notional canopy.
|Initial shape making: some exercises in basic aesthetics|
Once the base surface was frozen, a series of panellization exercises followed with the constants being that the in-house laser cutters were the only fabrication technique available, and plywood would be the most feasible material to procure and fabricate. So keeping in mind that planar panels out of plywood was the only way to go, we zeroed in on skewed hexagonal panels that formed gaps between them everytime the curvature was too high.
|Flattening the panels achieved dual objectives: easier fabrication and a porous structure|
Figuring out the panellization is one thing, figuring out how they're suspended in space is quite another. It was decided that the panels would be held by a triangular meshed network of thin steel cables, which in turn would be supported by laser cut wooden profiles fixed to a steel frame -- so far so good. Now came the part where we had to manage to fix panels to this cable network with a joint that allowed flexibility to move/rotate panels in all 3 axes. We 'invented' a custom detail that did exactly this:
|Generating a fool-proof numbering sequence in a hex-grid is tricky|
The laser cutters that we were working with had a bit of a problem: they were exceptionally slow at cutting curves, and even if we gave them segmented polylines, they would take a significant amount of time stopping at each junction and starting on the new segment. While the panels were all straight lines, the text became the killer. So we ended up inventing our own font that minimized the number of turns it takes to write a number, and obviously there were no curves. It's not the prettiest, but it saved about five minutes of laser cut time per panel, and there were 650 panels in total.
|Patterns in numbers: a screenshot of the excel file containing cable lengths.|
The cables had to be manually marked, cut and piled, and then clamped to the structure. The photos below should illustrate what a process this was.
|A carpenter making post-it tags from the excel files|
|The good ol' T-square. Cables being measured and tagged|
|Nobody wanted to be the one unrolling this back into straight lengths.|
|So far so clean: adding alternate cables in 1 direction looks fairly clean and simple|
|But it starts getting complicated fairly quickly|
|Reaching a point of near-incomprehensibility when done|
Here's some sequential shots of the fabrication process.
|Construction Sequence 1: Never assumes the walls to be vertical|
|Construction Sequence 2: Never assume the ground to be horizontal|
There's also a short video of the Rhino+Grasshopper setup that generated all the final design geometry and construction data: