The Marina Bayfront Pedestrian Bridge in Singapore features a double-helix to replicate the designersÝ vision of walking through a DNA molecule. The creation of this complex form was made possible with the help of BentleyÝs unique generative design software, GenerativeComponents (GC).

Arup, a leading global design and business consulting firm, knew from the beginning that completing the Marina Bayfront Pedestrian Bridge design project in Singapore would require innovative technology. The 280-metre-long bridge features a double-helix exoskeleton constructed from stainless steel to support a 6-metre-wide deck spanning 65 metres between piers. When it opens in 2009, the bridge will replicate for pedestrians crossing it the designersÝ vision of walking through a DNA molecule.

A string of computer-controlled lights along each helix will turn the bridge into an active element during evening fireworks displays and light shows. These multicolored lights are designed to mimic the chemical processes found in DNA replication.

What enabled the designers to pursue this inspired design was GenerativeComponents (GC) ± BentleyÝs unique generative design software that captures and exploits the critical relationships between design intent and geometry. GC allows architects and engineers to quickly explore a broad range of ýwhat-if¯ alternatives for even the most complex structures.

The Marina Bayfront Pedestrian Bridge project presented the type of design challenge for which GCÝs capabilities are well suited. The bridgeÝs DNA-inspired double-helix structural support mechanism is fundamentally unique. Unlike the Golden Gate Bridge in San Francisco and Millennium Bridge in London, which though different in appearance utilize conventional structural systems, the Marina Bayfront Bridge doesnÝt belong to any tried-and-tested bridge type.

Moreover, as an aerial view shows, the bridgeÝs centreline adapts to the site geometry, with the bridge curving in plan while simultaneously rising to a high point in the centre to create a shipping lane. Incorporating the plan curve and vertical geometry within the constraints of the helix rhythm required complex geometry. To understand that geometry and create the necessary drawings to accurately estimate construction costs and coordinate the design between engineering analysis and documentation, Arup needed an innovative 3D modeling solution.

ýThe main challenge that impacted our ability to coordinate the geometry was associated with finalizing the bridge centreline,¯ said Greg Killen, senior associate in ArupÝs Brisbane office and design manager of the Marina Bayfront Pedestrian Bridge. ýUltimately, it became a delicate balancing act to provide sufficient clearance for the shipping lane, as well as a gentle slope to move pedestrians comfortably along the bridge. We also needed to create a link to a nearby vehicle bridge, allow pedestrians to pass under the bridge at each abutment, and facilitate supports close to existing bridge supports to reduce the impact on ships navigating the bay.¯

The design team also understood that any project constructed around complex, nonrepetitive geometry often attracts premium pricing during the tender process. To avoid this, the Arup team deployed sophisticated geometric analysis to rationalise portions of the structure. By using BentleyÝs integrated software applications, Arup was able to take advantage of streamlined collaborative workflows that increased the efficiency and productivity of its project teams. For example, by deploying GenerativeComponents, the team could begin modelling the complex helix exoskeleton, even while finalizing the critical bridge centreline geometry, fully confident that the design could accommodate any late changes.