St. Patrick’s Footbridge in Calgary

Project: St. Patrick’s footbridge
Designed by Halsall Associates Limited & RFR
Location: Calgary, Alberta, Canada
Website: www.halsall.com
The design of the St. Patrick's Bridge will take its cues both from the urban and from the natural. The Bow River is a ribbon of nature winding through the urban environment of the city. For pedestrians and cyclists crossing the river, the footbridge becomes an instrument through which to observe, understand, and appreciate the spectacle of the river. View more after the jump:

One of the primary goals of the bridge architectural concept is to keep the supporting bridge structure located primarily above the deck. This basic trait leads to several important attributes.

Firstly, the bridge is supported solely from land, with the only supports below 100?year flood levels being those located on the river banks. This strategy has a number of clear benefits. From the viewpoint of the riverside pathways and river craft, the river corridor appears minimally occupied. During construction, turbidity from construction activity is reduced or eliminated, to the benefit of aquatic life. And finally, less structure in the river channel during floods means less accumulation of debris and associated pier scouring.

A second attribute of the architectural concept is that it creates a spatial sequence along the crossing. The rhythm of the continuous arches is aligned with the river channels and the island, giving visual cues to pedestrians that are synchronized with the surrounding environment. The lateral inclination of the arches leads to a feeling of a partially enclosed deck over each river channel, with the arches located overhead of the pedestrians. On the island, however, the arch structure remains below the deck, leaving bridge users in intimate contact with the island's verdant setting.

The architecture of the structure also contributes to its physical robustness. The resistance of the bridge to floods and ice floes is improved by limiting the number of elements located in the flood zone. The leaning geometry of the arches facilitates inspection of the arch, hangers, and struts, with the entire structure visible from the deck. The inclination of the arches also makes them more resistant to ice floes while remaining slender, by forcing ice upwards until it breaks and falls back onto itself. This is contrasted to a blunt vertical support that would receive large horizontal forces from the ice and would have to be quite stout as a result. – from CMLC