Abstract Manager

The bridge was originally built in 1959 over the Red River on PR 305, immediately east of the community of Ste. Agathe, approximately 25 km south of Winnipeg. The Ste. Agathe school is approximately 200 m west of the structure, surrounded by numerous residences and businesses. Farmland with sparse businesses and residences are to the east.

The structure was originally designed for HS20 loading and supported two lanes of traffic on four lines of steel girders. The bridge has 9 spans and is 243.84 m long. Severe deterioration of the girders and secondary structural steel members along with deterioration of the expansion bearings and concrete deck resulted in the the conclusion of the PD report for superstructure replacement including a wider bridge deck and six lines of new steel girders and substructure widening and strengthening.

The DD assignment consisted of PD follow-up, design of a major bridge rehabilitation including substructure modifications and strengthening, new steel I-girders, new widened concrete deck, and associated roadworks.

The new concrete deck was widened from 9.7m to 14.95m to accommodate larger traffic lanes and shy distances, and to include a new 2.7m wide multi-purpose sidewalk. Six lines of new steel girders were designed with four continuous segments to accommodate the existing substructure bearing seats while reducing the number of expansion joints on the bridge. The existing abutments were modified to be semi-integral design. The shallow girders on the east approach spans required specific design considerations to account for the rotation of exterior girders under construction loads.

The existing land piers were pier bents supported on CIP concrete caissons, the three river piers were standard monolithic piers supported on spread footings, and the conventional abutments were supported on concrete caissons. Widening of the abutments and land piers were accomplished bearing seat extensions and underpinning with new concrete caissons. The interaction of the new and old deep foundations was modelled to confirm how the bridge loads would be shared. The river piers were widened by extending the pier cap while maintaining acceptable design bearing pressures.

The new bridge minimized the change in vertical grade to avoid costs for approach roadways, Roadway safety was evaluated with several traffic calming measured for speed reduction implemented and a speed display device becoming part of the approved strategy. Roadway improvements include a new raised concrete island for turning movements and urbanized cross-section including barrier curbs, pavement widening, and bridge drainage.