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In 2008, The City of Ottawa (Ontario) authorized the construction of a new 3-meter-wide multi-use pedestrian and cycling bridge over the Airport Parkway and associated pathway connection between the Hunt Club Community to South Keys Transit Station on city-owned lands. The goal was simple: create an architecturally-appealing pedestrian bridge over the busy airport parkway. The reality, however, was the construction of the $5.3-million Ottawa Hunt Club Bridge would be a challenge.
With a wall inclination of almost 72-degrees and two fin-shaped walls that intersect at a height of 16-meters, as well as the creation of an inclined column to extend a further 16 meters, formwork would be key to success. As such, Doka was hired by concrete contractor Louis W. Bray Construction Limited to meet the challenge. Further to the complexity and size of the bridge pier, Doka also had the resources to provide abutment, slab, shoring, and stair tower formwork.
The project began in May 2012 and the geometry of the structure presented many engineering complications. Although it required a significant planning effort, pouring the bridge tower in two 17-meter pours made the most sense. The main challenge of the first pour was to incorporate the structural needs of the tower with avoiding interferences between various formwork members. The immense weight of the 900-mm thick inclined walls required tremendous external support. This was accomplished with a matrix of panel struts and supporting Eurex 60 props, ensuring safe load transfer into the base slab. These struts were interwoven with Eurex 30 props, which supported the working platform at the beam level.
Two transverse concrete beams to support the bridge deck and join the stay tower legs were to be poured at the same time as the legs. Therefore, the beam formwork was integrated into the 17-meter panels.
In addition, all formwork for the stay tower was designed to resist a pour pressure of 120kPa (2510 psf) resulting from the use of self-compacting concrete.
Doka used wall formwork Framax Xlife for the abutments and load-bearing tower Staxo 100 for the approach spans and the main span. The Top 50 Wall formwork with vertical C8 channels provided a safe working platform for easy access to bridge beam formwork with greater minimal tolerances. A 16-meter pour height with working platform was required every 3-meters in height. Screw-on access brackets were used for the exterior working platforms, while Doka floor props and Dokaflex slab formwork was utilized for the interior access platform. Safety brackets were used at multiple levels to protect workers and formwork panel reinforcing as well as monitoring of pressures exerted during pour by form tie load measuring devices ensured the project scheduled was maintained in a safe manner.
In addition to technical support and superior forming solutions, Doka helped the contractor save time by pre-assembling the panels and shipping them directly to the site. The project is expected to be completed in 2013.