Five to six freight trains a day cross the Canadian National (CN) Railway’s Warman Bridge, which was built in 1906 over the South Saskatchewan River. Given the age of the bridge, we paid careful attention to geotechnical and structural details at every phase.
Coordination and schedule flexibility were keys to success. CN scrutinizes track-closure windows carefully and appreciates a contractor that does not proceed with work until given the appropriate approval. With careful planning, we reduced total track-closure time from the 218 hours planned to 133 hours, minimizing disruption to rail traffic.
As soon as CN selected us to carry out the bridge rehabilitation, we did an extensive as-built survey of the existing bridge structure. This uncovered a slight difference in length between the original and the planned girders. The engineer designed a girder bracket extension for two of the girders in ample time for the steel supplier to fabricate it before we replaced the spans, leaving no changes to the schedule.
The bridge rehabilitation included the addition of six new bridge piers and strengthening of existing ones. Engineers developed structural steel for the new piers which was cast directly into the concrete to support and brace the custom formwork. We used an internal cooling system that cycled river water and embedded sensors in the concrete to continuously monitor and control temperatures while setting the piers.
The river served as a staging ground for placing the spans. CN shipped structural steel I-beams through the mountains to the project site and offloaded them directly from the bridge onto a berm we had placed in the river. We built the berms with enough space to accommodate the work and minimize track closures.
Much is on the line when a train crosses a bridge and safety is of utmost importance to CN. We monitored displacement daily to make sure railway traffic could pass safely over the bridge without harming workers or damaging railway operations. The rehabilitated bridge enables CN to continue transporting materials and goods around Saskatchewan and beyond.