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.
Issue link: http://www.aspiremagazinebyengineers.com/i/297024
The $115 million I-15 widening project from 500 North in Salt Lake City, Utah, to the I-215 junction in Davis County, added 4 miles of northbound and southbound express lanes to I-15. As part of the design-build project, the existing six-lane Beck Street Bridge was removed and replaced with twin, four-span bridges to carry a total of 10 lanes of traffic on I-15. The bridge replacement, including additional lanes, eased the heavily used commuter route. The northbound and southbound I - 1 5 B e c k S t re e t B r i d g e s a re t h e Utah Department of Transportation's (UDOT's) first bridges designed to re m a i n f u l l y f u n c t i o n a l a f t e r t h e anticipated maximum seismic event. At the time of construction, they also used the longest precast, prestressed concrete girders ever fabricated and erected in the United States. Improved Layout from Original Concept Plans The project team redesigned the concept plans for the I-15 Beck Street Bridges to reduce costs and complete the project 3 months ahead of UDOT's initial schedule. Warm Springs Road, the westernmost feature crossed by the I-15 Beck Street Bridges, was realigned 50 ft east, and vertical abutments were used instead of slope protection, resulting in a reduction of the overall length of the bridge by more than 200 ft. The reduction of the overall bridge length and the adjustment of the locations of the bents reduced the maximum span length to just less than 195 ft, allowing the use of precast, prestressed concrete girders rather than steel girders. The project team worked with the precaster during the proposal stage to select the girder section that could handle the long span. At the time, the standard Utah bulb-tee girders were still in development, but the precaster already had the data and the forms available for the metric, 2400-mm (94.5-in.) -deep, bulb-tee girder, which was selected for the project. The bridges cross Union Pacific Railroad (UPRR) tracks, Utah Transit Authority (UTA) commuter rail tracks, Warm Springs Road, U.S. 89/Beck Street, residential and commercial structures, pressurized natural gas and hydrogen lines, and two 10-in.-diameter crude-oil pipelines, and pass under a transmission power line. The geometric layout required approximately 45-degree skews at the abutments and bents. The bridges are on vertical and horizontal curves and featured a varying superelevation. The northbound bridge is 591 ft 8.25 in. long between centers of bearings. The approximate span lengths are 114.6, 185.5, 196.5, and 95.1 ft. The bridge width varies from 84 ft 10 in. to 92 ft 11 in. The southbound bridge is 603 ft 7.1 in. long between bearings. Its span lengths are 124.6, 175.6, 196.5, and 107 ft. and its width varies from 72 ft 10 in. to 77 ft 0.25 in. profile I-15 Beck Street BrIdgeS / Salt lake City, Utah brIdge desIgn engIneer: Parsons Corporation, Pasadena, Calif. geOTeCHnICAL/FOUndATIOn desIgn engIneers: Dan Brown and associates PC, Sequatchie, tenn., and Shannon & Wilson inc., Seattle, Wash. PrIme COnTrACTOr: kiewit/Clyde (a joint venture between kiewit Western Co., american Fork, Utah, and W.W. Clyde, Springville, Utah) CAsT-In-PLACe COnCreTe sUPPLIer: Geneva Rock, Orem, Utah PreCAsTer: hanson Structural Precast, Salt lake City, Utah, a PCi-certified producer sHAFT COnsTrUCTIOn: Malcolm Drilling Company inc., San Francisco, Calif. The I-15 Beck STreeT BrIdgeS A Tectonic Shift in Bridge Design Completed structure at Beck Street and I-15 (looking North) The crossing over two roads and the railroad, required a 45-degree skew on the abutments and piers. Photo: Kiewit/Clyde. by Corin Piacenti, Parsons Corporation designed to remain fully functional after the anticipated maximum seismic event. 36 | aSPiRe , Spring 2012 I-15_Spr12.indd 36 4/3/12 10:40 AM