Adel R. Zaki and Bernard Breault, SNC-Lavalin Inc.
The reconstruction of the Jacques Cartier Bridge in Montreal, Canada, involved more than 645,800 sq ft (60,000 sq m) of bridge deck and made extensive use of precast, prestressed, high performance concrete (HPC) deck panels. This case study demonstrates a good example of the benefits of using a precast deck replacement method to rapidly reconstruct a highly durable deck while maintaining normal rush hour traffic.
The 1.7-mile (2.7-km) long bridge with five traffic lanes carries more than 43 million vehicles every year, making it one of the busiest bridges in North America when considering traffic density per lane. After more than 70 years of operation, the concrete deck slab, support beams, and many other bridge deck components had suffered severe damage and had thus reached their useful service life. In-depth investigations confirmed that major reconstruction of the deck was required.
The new bridge deck is made of precast HPC panels, which form a modular multistem integral deck system that, after being installed on the bridge, is transversely and longitudinally post-tensioned to provide high durability. Specified concrete compressive strength was 8700 psi (60 MPa) at 28 days.
The precast concrete panels were designed to suit the various structural systems of the existing superstructure along the bridge. The new deck structural configuration was mostly driven by construction constraints and by the existing steel bridge components.
The new deck for the north and south approach spans consists of a series of deck spans, typically 24.34 ft (7.42 m) long. Each span is made up of four precast, prestressed concrete panels installed side-byside. Each panel has a 7-in. (180-mm) thick slab and incorporates three integral stems with depths ranging from 19.6 to 31.5 in. (500 to 800 mm). The stems are reinforced with four 0.6-in. (15.2-mm) diameter draped prestressing strands. The concrete barriers were also integrated with the panels. Following the installation of a specific number of panels on the existing floor beams, the transverse and longitudinal post-tensioning was applied. The deck panels for the approach spans represent 67 percent of the entire surface area that was reconstructed. For the main span, similar precast panels were used but having only two stems per panel.
Because of the size of the project and the large number of precast deck panels to be installed during the two construction seasons (April to October of 2001 and 2002), it was deemed advantageous to construct a temporary precasting plant near the south approach of the bridge.
On the bridge, the existing deck was removed by saw cutting it into sections having similar dimensions to the new panels. Existing deck sections, which included the slab, steel stringers, barriers, and railings, were removed using two self-propelled telescopic cranes placed at opposite ends of a panel. During the same lifting sequence and using the same cranes, the new panels, each weighing between 22 and 42 tons (200 and 375 kN), were lifted from the transport truck and lowered onto new bearing assemblies, which had been installed by other crews working in advance during the day. Joints between panels were 1.56 in. (40 mm) wide and were filled using a rapid setting mortar, designed to provide a 3600 psi (25 MPa) compressive strength at three hours after mixing and prior to post-tensioning.
In this project, the use of high performance concrete combined with a precast, prestressed, post-tensioned, modular multistem integral slab and girder system reflects the state-of-the-art in regards to bridge deck reconstruction where durability, speed of construction, structural efficiency, life-cycle costs, and impact to users are considered.
Further Information
For further information, contact the first author at [email protected] or 514-393-1000.