The pedestrian bridge Henderson Waves was commissioned by the Urban Redevelopment Autority (URA) of Singapore following an open international competition. The commission was awarded to IJP Corporation and RSP Architects, Planners and Engineers in 2004, with concept and scheme design engineering by Adams Kara Taylor Consulting Civil and Structural Engineers. This stunning piece of public infrastructure is one of three new linkways built by the Urban Redevelopment Authority in the Southern Ridges, at a total cost of S$25.5 million
Henderson Waves springs from a scenic location off Mount Faber and spans some 284 meters above Henderson Road, a six-lane freeway running through the south coast of the island state. This man-made structure, the largest of its kind in Southeast Asia, is smoothly integrated into the landscape.
Architecture
It has seven spans, six of typical size (3.5 meters high, 24 meters long), and a larger one (6 meters high, 57 meters long). The upside spans unfold above deck level and house temporary activities, such as seating, lounging and sight-seeing. The remaining spans unfold below deck level and are not accessible -simply ensuring the continuity of the structure.
Two inclined decks extend the bridge at both ends, linking it with existing pathways and plazas. The full length of the bridge runs close to 284 meters, and the difference in elevation between springing and landing is equal to the full height of a seven-story housing block.The design concept of Henderson Waves is based on a folded three-dimensional surface-form created by means of simple mathematics. The architect of the project used proprietary mathematical techniques to define its form simply and rigorously. Hence the form bends, undulates, and ascends by twenty-one meters in one movement; in the process it also deforms to provide adequate egress, sloping, shelter, and scenic viewing to pedestrians and cyclists.
Materials
The surface-form of Henderson Waves is made of steel and timber. Steel is needed for structural purposes, whereas timber celebrates the beauty of natural forms.
Steel
The primary structure of the bridge features a sequence of steel arches and catenaries (or down-facing arches) joined across, and resting upon, reinforced concrete pylons. These pylons (the tallest of which reaches 38m) sit between waves as it were, at the point where the surface-form self-intersects and tapers down to a single beam.
Timber
The 1,500 square meter timber deck sitting on top of the steel structure is the centrepiece of the project. The complex, doubly-curved portions of this large expanse of tropical hardwood form a tapestry of 5000 modular boards, each varying by a single degree every 10m -and many tapered to measure.The entire deck being supported on a steel sub-frame with vibration dampeners, the coordination of steel and timber became a challenging task. Using its proprietary equations, the architect issued precise numerical descriptions of the surface at regular 500mm intervals, and provided dimensional coordinates that greatly assisted the production of the timber manufacturer's shop drawings.
