Abstract Manager

The St. Vital Bridge over the Red River in Winnipeg, Manitoba, built in 1965, and rehabilitated in 1988, is a vital link within the City of Winnipeg’s transportation network, supporting the conveyance of approximately 44,000 vehicles per day. The nine-span continuous steel plate girder structure is 280 m long and supports two carriageways, each consisting of two traffic lanes and a 1.5 m wide sidewalk. The bridge superstructure is supported by hollow cast in place abutments founded on piles and solid shaft bridge piers founded on a combination of piles on the riverbanks and spread footings within the river. In 2021, the City of Winnipeg, in partnership with Morrison Hershfield Limited, began planning the structure’s rehabilitation to extend its service life by 50 years. The ultimate rehabilitation includes the removal, widening and reconstruction of the concrete bridge deck, steel girder strengthening through cover plate installation, bearing replacement, and preservation works. The project also includes associated road works to accommodate widened bridge geometry, Active Transportation improvements, and intersection improvements.

During the initial phase of construction in 2023, a shift in north riverbank pier position towards the river was identified, prompting a swift response to assess and stabilize the structure while construction was ongoing. This paper details the innovative analysis, design, and construction of the pier stabilization. Rigorous soil-structure interaction analysis, using Midas Civil to develop a three-dimensional analysis model of the pier, was used, which was ultimately capable of directly replicating the mode of movement within the pier. Nonlinear soil springs representing the detailed soil stratigraphy at the site was modeled, along with a sensitivity analysis of various vertical soil stiffness responses. The stabilization methodology involved offloading the riverbank, underpinning the pier using 28 steel H-piles, installed where ongoing bridge construction would allow, and a cast-in-place encasement pile cap around the existing foundation. 

The unique repair approach not only provided a robust pier stabilization but also increased the foundation capacity and was fully constructable. This paper discusses the analysis and construction details and challenges associated with stabilizing the footing under the constraints of ongoing traffic on one carriageway and construction on the other. The presented case highlights the importance of adaptive engineering solutions in addressing unforeseen issues and ensuring the longevity and safety of critical infrastructure.The project was executed by MD Steele Construction Limited, a General Contractor for this project based in Winnipeg.