THE CONCRETE BRIDGE MAGAZINE

SUMMER 2012

ASPIRE is a quarterly magazine published by PCI in cooperation with the associations of the National Concrete Bridge Council. The editorial content focuses on the latest technology and key issues in the Concrete Bridge Industry.

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52 | ASPIRE , Summer 2012 CBP Concrete Bridge Preservation Lightweight Concrete Facilitates Deck Replacement by Catherine Higgins, Utah Department of Transportation Lightweight concrete is not commonly used for constructing bridge decks according to Joshua Sletten, structures design manager at the Utah Department of Transportation (UDOT). However, lightweight concrete was the right choice for the Tag- gart Bridge, which is comprised of twin structures that carry I-84 over the Union Pacific Railroad. Originally built in 1967, the deck replacement was a priority. Lightweight concrete al- lowed the bridge deck to accommodate a thicker deck and as- phalt overlay to meet the adjoining freeway profile, while not exceeding the load capacity of the older, precast, prestressed concrete girder bridges. The bridge geometry, along with the requirement to keep the freeway open during construction, presented the initial challeng- es to UDOT, Hanson Structural Precast, and Granite Construc- tion Company Inc. Both bridges are three-span structures on a curved alignment. Sixty individual deck panels were designed, and "no two pan- els were the same," according to UDOT design engineer Robert Nash. He kept dimensions the same where possible but "the lo- cation of shear blockouts and leveling devices were different for every panel." Each panel was connected to the beams using rein- forcing bars grouted into the top flanges of the concrete beams. Hanson created precise shop drawings for each precast con- crete panel. An indoor precasting yard made production immune to weather delays, and a rigorous internal quality- control process eliminated fit issues at the construction site. Panels used concrete with expanded shale lightweight aggre- gates from Utelite Corporation, a local supplier. Granite Construction achieved UDOT's aggressive construc- tion schedule requirements while keeping traffic moving dur- ing construction. The precast concrete panels and detailed construction sequence allowed workers to keep pace even during snow flurries and low temperatures. The project won recognition from UDOT as the Rural Project of the Year for 2011. _________ Catherine Higgins is an interactive specialist with the Utah Department of Transportation Communications Office. CBP CONCRETE BRIDGE PRESERVATION Lightweight concrete panels allowed the use of a thicker deck and overlay while not exceeding the capacity of the older beams. Photo: Utelite Corporation. The panels were connected to the beams through reinforcing bars grouted into the top flanges of the beams. Photo: Utelite Corporation. ASPIREBook_Sum12_R02.indb 52 6/29/12 12:39 PM

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