The St. Vital Bridge over the Red River in Winnipeg, Manitoba, built in 1964 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 vaulted 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 retained Morrison Hershfield Limited and began planning the structure’s rehabilitation to extend its service life by 50 years. The current 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 the position of Pier 3, the north riverbank pier, towards the river was identified, prompting a swift response to assess, design, and stabilize the pier while construction of the current rehabilitation 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 replicated the mode of movement within the pier. Nonlinear soil springs representing the detailed soil stratigraphy at the site were modeled. The stabilization methodology involved offloading the riverbank, underpinning the pier using 28 steel H-piles, which were installed where ongoing bridge construction and the existing pier footprint would allow, and casting a reinforced concrete encasement pile cap around the existing foundation and additional piles.
The unique repair approach provided a robust pier stabilization and increased the foundation capacity while being constructable within the required project timelines and dimensional constraints. This paper discusses the analysis and construction details, and challenges associated with stabilizing the pier under the constraints of ongoing traffic on one unrehabilitated 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 M.D. Steele Construction Limited, a General Contractor for this project based in Winnipeg.
