Provencher Bridges

Aesthetics and architecture are becoming more and more important in bridges and other civic structures. When it came to replacing the 90-year old Provencher Bridge, the city of Winnipeg took the lead and moved beyond cold “utilitarian” structures of the past, and adopted a vision of design that respects aesthetics and beauty. It called for a landmark design for the new Provencher Bridges as a symbol of commitment to the renewal of Winnipeg’s downtown core.

The concept was the result of an extensive two-and-a-half year public consultation process with Wardrop as the primary consultant.

The unique paired bridges design that was ultimately decided on consists of a suspended pedestrian bridge and a four-lane vehicular bridge that branches off from a shared abutment on the east bank. Located near the junction of the Red and Assiniboine Rivers, the structure provides a crossing over the Red River and links the Forks, a national historic site, on the west, and St. Boniface, the city’s vibrant French Quarter to the east. As prime consultants, Wardrop designed the bridges and provided contract administration and resident engineering services during construction. Gabourey Prfontaine Perry provided architectural design from concept to completion of the project.

The 280-metre concrete vehicular bridge includes innovative features such as rock-socketed, steel-jacketed concrete caissons constructed to high elevations that eliminated the need for massive excavations and cofferdams. The caisson innovation also allowed work to be easily completed in the winter season, avoiding the problems of the spring ice-break up and floods.

To avoid traffic and business disruptions the bridges were built in phases. The vehicular bridge was begun in 2001 and completed in October 2003.

The dramatic pedestrian bridge is a 5-metre wide, 250-metre long people path that melds art, architecture, and engineering. The bridge follows the alignment of the historic Broadway Bridge, which collapsed during a spring flood in the early 1900s.

Cable-stayed from a single, transversely inclined pylon rising 57 metres above the Red River, the bridge design reflects the lightweight nature of its pedestrian traffic, while the spire signifies a place of meeting in the middle of the Red River. All the structural elements rise to this one focal point, reflecting the richness of its surroundings and a celebration of the many cultures that have always come together along these historical banks.

The tender called for precast concrete girder and deck sections but gave bidders the opportunity to propose alternatives. The cast-in-place deck system was $2 million less expensive than the precast alternative.

As in days gone by, the bridge will be a focus for commerce and festivities. The spire base has a 370-m2 restaurant and a large, multipurpose gathering plaza and commercial kiosks. The bridge opened in December, 2003 and was named the Esplanade Riel. “Walking on the pedestrian bridge is pretty awe-inspiring,” said Jim Thomson, director of Public Works for the City of Winnipeg. “It gives one the impression of walking in an outdoor cathedral.”

Engineering and monitoring

Because a single inclined cable-stay pylon bridge design incorporating a restaurant building has not been done before, extensive engineering analysis was necessary. This included the building of a 1:60 scale aeroelastic model and wind tunnel testing with sub-consultant Rowan Williams Davies & Irwin (RWDI) in Guelph, Ontario.

A computer-based structural health monitoring system measures and reports key parameters for the ongoing health of the new infrastructure. Wardrop along with JBMT Structures Research and ISIS Canada designed the system with a nerve network consisting of sensors, fibre-optic cables and a “brain” represented by the data acquisition system. The interactive system is monitored remotely and incorporates conventional electric strain gauges, thermocouples, unidirectional and tri-axial accelerometers, a wind monitor, inclinometers, and a web camera. The equipment constantly gauges the “heartbeat” of the bridge as it responds to changes in temperature, wind velocity and people-induced loads. The goal is to identify problem areas more quickly than by traditional methods and tbereby reduce the client’s maintenance costs.

The total project costs are now at $72.5 million, which include the vehicular and pedestrian bridges, approach roadways, underground works and utilities. Landscaping works will be completed this spring.

As an added bonus, engineering students at the University of Manitoba were able to participate in the project through the Intelligent Sensing for Innovative Structures (ISIS Canada) and Natural Sciences Engineering Research Council of Canada (NSERC) programs.

Client/owner: City of Winnipeg

Prime Consultant: Wardrop Engineering, Winnipeg

(Doug Stewart, P. Eng., Robert van Ginkel, P. Eng.,

Bob Kurylko, P. Eng., Rick Haldane-Wilsone, P. Eng.,

Dr. Dezi Yang, P. Eng., Dr. Emile Shehata, P.Eng.,

Gene Piasta, P. Eng., Darren Burmey, P. Eng.)

Architects: Gaboury Prfontaine Perry architect.e.s.

Other consultants: Rowan Williams Davies & Irwin

(wind tunnel testing), JMBT Structures Research,

ISIS Canada (monitoring); Manitoba Hydro (hydraulics),

Dyregov Consultants (geotechnical);

Hilderman Thomas Frank Cram (planning/landscape)

Peer review: Speco Engineering

Contractor: M.D. Steele Construction