THE CONCRETE BRIDGE MAGAZINE

SPRING 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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A precast, prestressed concrete bulb-tee girder during transport to the project. At 194 ft 5 in., the girders were the longest used in the United States at the time. Photo: Hanson Structural Precast. the use of long precast concrete girders was vital in accelerating the schedule, minimizing impact to the railroads, and reducing costs. Use of Precast elements The bridges use 194-ft 5-in.-long bulb- tee girders with shipping weights of approximately 242 kips. The 92 girders have a depth of 7 ft 10½ in. and are flared in the end spans to accommodate a varying roadway width. The center- to-center spacing of the girders varies from approximately 6 ft 9 in. to 7 ft 7 in. Steel was used for the intermediate diaphragms. The girders are heavily pretensioned, using up to sixty-eight 0.6-in.-diameter prestressing strands. The total jacking force was 2988 kips— 791 kips in the 18 harped strands and 2197 kips in the 50 straight strands. The engineer used prestress bed capacity information from the precaster to guide the girder designs. The girders required 8500 psi compressive strength concrete to reach the desired span length. The specified strength of the concrete at prestress transfer was 6500 psi. The girder bearings are 5¼-in.-thick reinforced elastomeric pads. The use of the long precast, prestressed concrete girders was vital in accelerating the schedule, minimizing impact to the railroads, and reducing costs. The girders were shipped 18 miles to the construction site supported on each end by trailers specifically constructed for their transport. They were then lifted from the trailers and walked into place using two 250-ton crawler cranes. The precaster placed three monostrands in each edge of the top flanges of the girders. These helped to improve stability and mitigate tensile stresses in the girders' flanges during stripping, shipping, and erection. The monostrands eliminated the need for external bracing and were cut to detention them following erection. Keeping with UDOT's commitment to incorporating accelerated bridge construction elements during design, partial-depth precast concrete panels were used in the 8½-in.-thick composite bridge deck. The 3.5-in.-thick, precast concrete panels, ranging from 3 ft 7 in. to 4 ft 7¾ in. wide and from 3 to 8 ft long, span between the girders and serve as stay-in-place forms for the bridges' cast-in-place concrete deck. These allowed the project to avoid installation and removal of forms over the railroad and was estimated to have saved an additional 6 to 8 weeks of construction time. The design compressive strength of the panel concrete was 5000 psi. tWiN, PReCaSt, PReStReSSeD CONCRete BUlB-tee GiRDeR BRiDGeS With COMPOSite, CaSt-iN-PlaCe CONCRete DeCk ON PReCaSt CONCRete DeCk PaNelS / Utah DePaRtMeNt OF tRaNSPORtatiON, OWNeR deeP sOIL mIXIng: hayward-Baker aGC, Odenton, Md. brIdge desCrIPTIOn: twin, four-span precast, prestressed concrete bulb-tee girder bridges with partial-depth precast concrete deck panels and with cast-in-place concrete piers, abutments, wing walls, and foundations sTrUCTUrAL COmPOnenTs: Ninety-two 7-ft 10½-in.-deep bulb-tee girders with a maximum girder length of 194 ft 5 in., 48,333 ft 2 of precast 3½-in.-thick deck panels made composite with 5-in.-thick cast-in-place concrete, and twenty-four 9-ft 2-in.-diameter drilled shafts with a maximum depth of 122 ft AwArds: 2011 PCi Design awards, honorable Mention, Main Spans Greater than 150 Ft, 2011 american Council of engineering Companies, Utah Chapter, Structural Systems Grand award; 2010 Roads & Bridges , No. 9 top ten Road Projects; 2010 Utah Department of transportation, Urban Project of the year. Each girder weighed up to 242 kips. Photo: Hanson Structural Precast. aSPiRe , Spring 2012 | 37 I-15_Spr12.indd 37 4/3/12 10:40 AM

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