COWI approaches critical stage in cantilever construction of Oakville bridges
October 31, 2023
Consulting engineering firm COWI and Bot Construction Group report they are approaching a critical stage in the cantilever construction of two new bridges over Sixteen Mile Creek, part of the William Halton Parkway extension project in Oakville, Ont.
The firms have been building a three-span bridge with a typical cast-in-place segmental construction technique, using a movable form traveller system. Soon, however, they will reach a section of the west pier cantilever where segment casting will proceed in a single direction toward a west abutment, for which COWI and Bot will use a uniquely adapted unbalanced cantilever method to complete the bridge.
“The casting of the first segments are often the most challenging areas in segmental bridge construction, due to the complexity of rebar details, the learning curve for casting procedures and the absence of accurate project data to reflect the performance of the form traveller on the specific structure,” explains Ivan Liu, senior bridge engineer with COWI. “Having worked on a number of similar projects across North America, we were able to lean on historical project data to provide informed engineering support for construction scenarios and estimations on the form traveller behaviour.”
The portion of the extended cantilever will be supported by a temporary stay cable tower, which will anchor supporting stays at each of eight ‘unbalanced’ segments. For this purpose, COWI designed a unique steel anchor box to enable the load transfer of the supporting demands of the cable stay tower to the concrete segment. This mechanism not only has minimized the need for top slab concrete modifications, as compared to the original designs, but also should ensure a clean extraction of the cable stay tower once the bridge is completed.
The construction of the north bridge is progressing, with Bot’s on-site team having installed segments on the west and east pier cantilevers. Bot and COWI are now aiming to complete the cantilevers to a point where they can cast the span closures.
Spanning 280 m, the two bridges will each host two lanes and pedestrian walkways, connecting Third Line to Neyagawa Boulevard, in an area with growing traffic congestion. COWI is responsible for construction analysis, geometry control, erection manual and construction support of both bridges, along with the design of temporary work structures.
The bridges are expected to be completed by fall 2024 and the William Halton Parkway extension should open to the public by 2025.