The main objective was to build a bridge that the public would feel positive about and would enjoy using. Castlemore were able to see this bridge as an iconic feature for their development, appreciating that the design was as much a piece of art as a structure. They remained very supportive and involved
throughout the design and fabrication of the bridge. The judging panel was particularly keen on a low maintenance bridge.
Before designing anything, the design team, Niall McLaughlin Architects, Price & Myers Consulting Engineers and the artist Martin Richman, began separately listing the most important qualities that the new bridge should have. There was an immediate consensus of ideas based on the nature of the site and the concept for the bridge. It was decided the bridge would be a singular construction of apparently extreme simplicity.
This has partly been achieved by using perforated stainless steel as a main feature of the bridge; creating the visual impression that the bridge is reflective, constantly changing and adapting to its surroundings during the day, whilst at night the lighting integrated within allows the bridge to be lit up across the river.
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The ribs and stressed skins form a strong torsion box, similar to the structure of an aircraft wing. The perforation of the stressed skins mean the bridge is as transparent as possible. However, during design it was recognised that in the highly stressed areas, the holes would reduce the capacity of the panels; therefore the density of the holes was decreased according to the level of stress in the skins. This process optimises the structural weight crucial for bridges.
There was no literature on perforated plates, so Price & Myers carried out some internal research using 3D analysis models to determine the capacity of the panels with holes for both static loads and buckling. The pattern of stresses for the bridge were analysed using a detailed space finite element model with skins modelled as plates. A bespoke computer program was written to convert the shaded stress diagram into a series of numbers representing the stress
across the surface of the bridge. The numbers were arranged in a spreadsheet, which was then read by 3D computer modelling software Digital Project, and each hole was sized accordingly.
The balustrade surfaces are skewed. However, the sheets of stainless steel are laser cut flat. The mathematical transformation of the finished formed panels into flat panels was a complicated operation, which required some elaborate software analysis. Price & Myers provided the steel fabricators with the unfolded profiles of all the skins and holes, and a laser cutter, controlled by the engineers' drawings cut the metal. The laser cut the exact shapes to fit
onto the bridge's skeleton, as well as the perforations. A sustainable feature of the project that also minimises life cycle costing was the decision to fabricate the bridge entirely from Stainless Steel, which doesn't require any paint or other protective coating for the full life span.
Structural Design – Price & Myers LLP
Architect – Niall McLaughlin Architects
Consultant Artist – Martin Richman
Client – Castlemore Securities
Contractors – Dean & Dyball
Steelwork Contractor – M –Tec
Cost - £2.4m
