The Infinity Bridge is a 230-metre suspension footbridge supported by a pair of asymmetric steel arches that appear to spring across the river like a pebble skimming the water.
Speirs and Major Associates (SaMA) designed the lighting so that the twin arches are reflected in the water and form, at night, the mathematical symbol for infinity (∞), hence the name.
The designers bounced blue light off the water to illuminate the underside of the bridge, creating a blue band between the two. Cool white light was used to reveal the structural form and to create the impression of a floating wave hovering just above the bridge.
As in every SaMA design, all the lighting equipment was carefully concealed. The luminaires were mounted on the counterweights, away from the bridge, so that pedestrians have no line of sight to the sources and are therefore not troubled by glare.
Along the bridge deck, the lighting is programmed to respond to the presence of people, guiding them and alerting them to the approach of others. Purpose-built blue and white LED units are hidden beneath the handrail.
Each LED unit uses a maximum of 3W for both colours, but the two never light at the same time. In effect, then, no unit ever exceeds 1.5W. There are around 200 units in total lighting the bridge. When people cross it, sensors trigger a change from blue to white, leaving a trail of light like a comet.
As far as we know, this design is unique. Entered in the structural engineering awards, the project proved highly competitive, going up against around 100 entries from all over the world.
Video: Expedition Engineering
Source: Mondo Arc
Photo: James Newton
Lighting design: Speirs and Major Associates
