Flexifloat Assists Arch Installation Across North Saskatchewan River.

Acciona/Pacer Joint Venture (APJV) is tasked with replacing the 100-year-old Walterdale Bridge in Edmonton, Alberta, a $155 million project scheduled to be open to traffic in 2017.

The new bridge will consist of two 183-foot-tall arches spanning approximately 630 feet across the North Saskatchewan River. The arches will be supported by thrust blocks on either shore, creating a clear span across the river for the three-lane bridge including a pedestrian walkway.

APJV planned to construct the arches in subassemblies, with two being supported on each shoreline with temporary support towers. The 277-foot-long center subassembly was to be constructed onshore and transferred out over the river using a hydraulic skid system. Once over the river, the center arch section was to be supported on barges and maneuvered to its final position between the arch assemblies onshore. Due to the river being relatively shallow, floating the 1,047-ton center arch section presented a challenge for the contractor. APJV consulted Robishaw Engineering to determine if floating such an arch section with minimal draft was feasible. Robishaw engineers concluded that two 120’ x 70’ x 7’ Flexifloat assemblies would provide the buoyancy and stability needed under the load of the arch, plus an additional 110 tons of ancillary equipment and support structure.

In November 2015, the 1,047-ton center arch section was slid out over the river and transferred to two Flexifloat assemblies in an intricate maneuver of land-to-barge load transfer (See Arch Span Float-In Time Lapse video in sidebar) Ballast was used to position the Flexifloat assemblies under the arch and then lift it off of the skids onshore using the force of buoyancy. With the arch fully supported by the Flexifloats, deck mounted winches were used to position the barge assemblies and arch between the soon-to-be complete arch sections on shore. Once all arch sections are completed, strand jacks will be used to elevate and assemble the arch subassemblies.

For more information, please visit the City of Edmonton’s website.