Peoria Street Pedestrian Bridge
Reconstruction of the Peoria Street pedestrian bridge spanning I-190/Congress Parkway and adjacent to the rebuilding of the busy circle interchange in downtown Chicago, IL, capitalized on innovative precast concrete Accelerated Bridge Construction (ABC) techniques that allowed for high strength, thinner bridge sections and reduced delays and lane closures.
The innovative, 271-linear-feet bridge, completed in the summer of 2015, includes 15,272 square feet of 8-inch precast deck panels that were set transverse to the main longitudinal I-beams in just four working days. The panels were formed with exposed vertical rebar and light pole anchor bolts so the contractor could pour a concrete parapet structurally integral with the deck.
“Typically, this would have been a full depth cast-in-place deck,” says Tom Heraty, VP of Sales and Engineering for Utility Concrete Products. “Utilizing precast, we were able to pour the slabs at our own pace in a controlled environment without the high cost of jobsite delays. It is also much safer to produce these slabs in a plant versus above the high-traffic I-290 expressway.”
Producing the precast concrete deck panels in a controlled setting with high strength, 5,000 psi concrete allowed for a thinner section than typical deck panels with less rebar clearance, but with the same or better durability and structural capacity. The precast panels were produced with a raked finish to create a rough pouring surface for the 2¼” overlay.
Tapered pockets were formed into the panels allowing rebar to pass through. These pockets and the edges of the panel were treated with retarder to create a porous surface for bonding. The edges were formed with shear keys and exposed rebar to help create a continuous structural connection across joints.
Panels were aligned so the pockets were set over vertical headed anchor studs from the top flange of the I-beams below. Rebar extending horizontally out of the edges had to be staggered such that it did not interfere with the overlapping bars from adjacent panels. Panels also included cast-in inserts with leveling bolts for vertical adjustability. Ductal (Lafarge), ultra-high performance concrete, was used to fill the pockets and joints to ultimately create a composite section.