Inauguration of the Peace Bridge in Calgary on March 24, 2012.
Peace Bridge is a bridge with a helix structure composed of two tangential radii that create a unique architectural space. The bridge accommodates people walking and cycling across the Bow River in Calgary, Canada. The design from Santiago Calatrava follows strict requirements with no piers in the water and restricted height. A minimally profiled structural tube was the design solution.
Photo: Bernard Spragg
The high-strength, welded-steel frame forms two intertwined helixes wrapping an elliptical cylinder. To simplify manufacturing, the purity of the geometry had to be altered: The form of the cylinder was modified to have a curvature based on several circular radii instead of an ellipse’s continuously changing curvature.
The stiff, helical frame serves as the truss web that transfers loads between the truss chords—linear steel members along the bridge’s top and bottom. Transverse strength is provided by two edge beams and the bridge deck.
Photo: Bernard Spragg. NZ
“Although the helical frame’s welded-steel box sections maintain a constant 300-millimeter-wide-by-250-millimeter-tall cross section, there is no ‘typical’ helix component,” Calatrava says. Each box is made from plates of different thicknesses based on the particular stresses experienced at its location. Even with the material optimization, the steel helixes and deck still weigh about 700 tons. Bent structural glass between the curved steel frames forms the roof canopy over an open-air bridge deck, supported by diagrid steel decking, with lightweight cement as the surface.
Photo: © www.calatrava.com
The bridge is a departure from Calatrava’s previous designs, which were typically asymmetric shapes anchored by high masts. Another atypical element is the color; while most of Calatrava’s designs are white, the Peace Bridge features red and white as used in both the Flag of Canada and the Flag of Calgary.
About the Author:
Bruno Dursin – Managing Director at Believe in Steel. Bruno has more than 30 years of experience in promoting steel & steel solutions. His clients benefit from his extensive network within the building industry.
