Saint Patrick's Bridge, Canada
Description: In 2009, CMLC launched a design competition that attracted more than 30 international concepts for the pedestrian bridge and engaged thousands of Calgarians who provided feedback on the concept CMLC selected – the “skipping stone” bridge imagined by RFR Halsall.
Construction of the new St. Patrick’s Island Bridge began in September 2012 with crews establishing temporary beams to support the base and bridge deck structure. At the same time, [we] – the steel fabricator charged with fabricating the span sections – began fabricating the steel arches that will form the graceful spans of the new bridge. Registering lengths of 16 to 36 meters and weighing 30,000 to 36,000 kg, these arches crossed Canada on transport trucks and arrived in Calgary on February 28, 2013. They will be welded together on-site with the help of a 250-tonne crane.
In parallel with the steel arch assembly, the bridge’s concrete deck will be poured and tensioned. Once these steps are completed in Fall 2013, the bridge cables will be connected and steel will be painted. The new bridge is expected to open, as planned, by year end.
Special Challenges: Tekla was instrumental in the geometry aspect of the bridge. The arches are composed of two side-by-side HSS16”x1” tubes with a 1” plate on the top and bottom tangents. The plane of both inclined arches were different but followed the same elevation line (when a true elevation view was taken, only one HSS profile had to be seen). Therefore, the top and bottom plates had torsion in them and the macros “triangle generation” and “unfold surfaces” were used extensively. The cable brackets were a challenge also, using the customers DWG rendition of the cables in the final and cambered positions, we had to simulate the correct fabrication condition. The difficulties of fabrication were reduced by using target layout points at crucial points. The long haul of 2450 miles from fabrication site (Terrebonne, Quebec) to erection site (Calgary, Alberta), induced large shipping frames with an exact CofG on truck bed centerline.