INFRASTRUCTURE SCALE 05 — COMPLEX Millpede 2025 · Competition Finalist

Topology Bridge

1,247 optimization iterations reduced a 120m span to 42 fewer tons of steel.

OVERVIEW

The competition brief asked for "a pedestrian bridge that is also a sculpture." Most entries delivered sculptural forms with structural systems hidden inside. We inverted this: the structure *is* the sculpture.

Using topology optimization (TO), we defined the 120m span as a design domain and let the algorithm erode material where stress was lowest. The result is a skeletal, branching form that echoes natural bone structures—maximum strength with minimum material. 1,247 optimization iterations produced a geometry that achieves 30% steel reduction (42 tons saved) while exceeding the required 1.5× safety factor.

The complex nodes are fabricated using Wire-Arc Additive Manufacturing (WAAM), a 3D printing process for steel that eliminates traditional welded connections.

THE CHALLENGE

Span 120m across the Hangang River with zero supports in the water (to protect the wetland habitat), while meeting seismic zone 2B requirements and a pedestrian load of 5 kN/m².

OUR APPROACH

Research-Driven Design

Topology Optimization

We discretized the design domain into 2.4 million voxels, defined load cases (dead load, live load, wind, seismic), and ran 1,247 iterations in Millpede. The algorithm removed 68% of the initial volume while maintaining stress limits below 240 MPa.

Real-Time FEA Validation

Each optimization iteration was validated in Karamba3D. We rejected geometries with nodal displacements exceeding L/500 (24mm at midspan). The final form has 18mm maximum deflection under full load.

WAAM Node Fabrication

The 48 primary structural nodes are too complex for traditional fabrication. We specified WAAM (Wire-Arc Additive Manufacturing) with 316L stainless steel. Each node is printed in 12–18 hours, then CNC-machined for connection surfaces. Prototype node tested to 1.8× design load before failure.