The bridge of the Topology Bridge, carved out of its block by BESO Topology. The block is steel, 16 m long, 2 m wide and 4 m high, pinned along both ends of its bottom, its top layer a deck kept solid under 10 kN/m². BESO starts from the whole block and takes 2% of what is left away each iteration - the bricks that work least go, and some come back - until a fifth of the block below the deck is left. Every brick is solid or void all along, so every iteration is a design of its own.
INFO
Without a license, BESO Topology runs on models of up to 500 elements. At 3 bricks per metre this one has 3 456, so it needs one; at 1 brick per metre, 128 bricks, it runs without.
The model
| Group | What it does |
|---|---|
| 1 - How fine | Bricks per metre, the same every way. The Expressions turn it into the bricks along and across, the height of a layer and the number of levels. |
| 2 - The design domain and the deck | The plan, a 16 x 2 m rectangle, meshed once with Mesh Plane, copied up level by level and made into bricks between each pair of levels by Mesh Series to Brick. The domain runs from the bottom to the deck's underside; the deck is the one layer above. |
| 3 - Steel, and the bricks | An nD material, steel with E = 210 GPa and ν = 0.3. Two sets of SSP Bricks, named Domain and Deck through their ElementId. |
| 4 - Pinned ends, and the deck load | The nodes along the bottom of both ends, held in X, Y and Z by a Support. The deck load, 10 kN/m² over 32 m², shared among the nodes of the deck's top as Point Loads, in a Load Pattern. |
| 5 - Assemble Model | Assemble. Model View is disabled: enable it to see the domain, the supports and the loads. |
| 6 - BESO Topology | Keep names the Deck. VolumeFraction 0.2, Iterations 200, Run, and Step to go through the designs. Panels show the compliance, the volume of each iteration, whether the run converged, and its history. |
| 7 - The design, analysed | Run Analysis on AlpacaModel, the design shown as a model of its own, and View Results colouring it by Von Mises stress, with a Legend. Run Analysis and Legend are disabled: enable them once the run has stopped. |
Running it
- Set Run to
true. The run goes on its own thread, so Rhino stays free, and the Surface preview and the outputs follow it. - Volume comes down from 1 to 0.2 in about 80 iterations; then the design settles. At 3 bricks per metre the run converges after 105 iterations, in under 20 seconds on an Apple M2 Pro.
- Drag Step back to go through the designs: each one is a bridge of the volume reached, from the whole block down. Choose the one you want.
- Once the run has stopped, select Run Analysis and Legend and enable them. Disable Run Analysis again before dragging Step, or every design shown is analysed.
What it shows
The steel goes into two inclined legs that rise from the supports into the deck, with a column up to the deck near each end: a deck on two raking struts, every brick of it solid, with no grey density to threshold.
Early on, the block opens a hole above mid-span and the underside comes away from the supports; by half the volume the legs are there, and the rest of the run thins them.
