Concrete Products

APR 2018

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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www.concreteproducts.com April 2018 • 49 TECHNICAL TALK 2018 TRB MEETING BONNER BRIDGE: MILES OF PRECAST PERFORMANCE A new causeway connecting mainland North Carolina with the South Outer Banks islands features extensive use of precast concrete con- struction for quality, durability, economy, and constructability, say Domenic Coletti, P.E., R. Dominick Amico, P.E., Elizabeth Howey, L.G., P.E., John Jamison, AICP, HDR Engineering, Inc. of the Caroli- nas; Nicholas Burdette, P.E., HDR, Inc., Pittsburgh; Phil Dompe, P.E., INTERA, Inc., St. Augustine, Fla.; and Mohit Garg, P.E., HDR, Inc., Tampa, in their 2018 TRB paper, Bonner Bridge – Miles of Precast Concrete Provide Economy and Durability. The 2.8-mile-long bridge also features a first-of-its-kind driven pile foundation verification method, and innovative, environmental- ly-sensitive construction approaches. The use of precast bent caps and columns instead of cast-in-place concrete for the pile bents and two-column bents resulted in substantial savings for both overall schedule and cost. Completion is on-target for November 2018. In 2011, the North Carolina Department of Transportation selected a design-build team of PCL Civil Constructors as the contractor, and HDR Inc. as the designer. The $246 million replacement will provide a modern link to Hatteras Island with a 100-year service life. As the lead design firm, HDR provided all roadway, geotechnical and bridge design services, as well as environmental permitting services. The centerpiece of the project is a 3,550-ft.-long, 11-span, seg- mental concrete box girder bridge. This massive structure provides nine 350-ft. spans, any of which can accommodate the shifting posi- tion of the navigation channel through the Oregon Inlet. According to NC DOT, stainless reinforcing steel and high-durability concrete will be used to protect against corrosion, with high-perfor- mance concrete the primary reason for the bridge's increased life span. The agency's request for proposals included numerous prescrip- tive requirements for the concrete mix designs, among them extensive use of fly ash or ground granulated blast furnace slag and silica fume; low water-cement ratio; and, use of a calcium nitrite corrosion inhibitor admixture. The Bonner Bridge will be the first North Carolina crossing using stainless reinforcing steel, providing additional protection against corrosion, while reducing rehabilitation and maintenance costs. The structure will have 12-ft.-wide travel lanes and 8-ft.-wide shoulders, which will improve safety. The existing bridge has no shoulders. (A one-minute visualization of the replacement process may be seen at https://www.youtube.com/watch?v=15DKyJvG3Qc.) A tailored design approach allowed widespread use of repetitive construction elements, Coletti, Amico, Burdette, Dompe, Garg, Howey, Jamison write. "The salt-water environment and the RFP's emphasis on durability, corrosion resistance, and a 100-year service life indi- cated the need for a concrete structure, while the remote location of the project site also suggested broad use of prefabricated elements and modular construction," they say. "All indicators pointed to the use of precast concrete as the optimum design solution." Extensive use of precast concrete elements offered multiple advantages, they continue. First among these were durability and quality. "Precasting FIB [Florida I-Beam] girders, box girder seg- ments, bent caps, columns, and piles in an off-site precasting yard, under controlled conditions, results in the production of extremely high quality, durable concrete elements; these levels of quality and durability would have been difficult to achieve in the harsh marine environment of Oregon Inlet," they add. The precast elements are also very economical; fabrication off-site is much less costly than trying to deliver and place CIP concrete to the remote project site. "The precast elements used in this project are generally very simple and employ significant repetition of detailing," the authors write. "This repetition of detailing led to significant economies of scale in terms of fabrication and familiarity in terms of construction, again reducing costs and speeding up construction." The extensive use of precast concrete elements—3.4 miles of cyl- inder piles, 12 miles of square piles, 0.58 miles of bent caps, 0.30 mile of column members, 8.75 miles of FIB girders, and 0.67 miles of segmental box girders—greatly enhanced the quality and durability of the structure, while simultaneously facilitating faster, safer, and more economical construction, Coletti, Amico, Burdette, Dompe, Garg, Howey and Jamison contend. The use of precast bent caps and col- umns instead of CIP concrete for the 44 pile bents and 25 two-column bents resulted in substantial savings for both overall schedule and cost, they add. The design-build team was able to develop an extremely econom- ical, durable, constructible design, and foster a spirit of partnership with NC DOT and various affected agencies, resulting in construction approaches which minimize both temporary and permanent environ- mental impacts, the authors conclude. "The value of this approach was demonstrated by the bid prices for the project—the PCL Team's bid was $64 million less than its nearest competitor," they write. Bonner Bridge south approach span construction, showing 96-in.- deep precast concrete Florida I-Beam (FIB) girders supported by precast bent caps and 54-in.-diameter precast cylinder piles. One of 673 precast pilings, ranging in length from 110 to 130 ft., is installed early in Bonner Bridge project. PHOTO: North Carolina DOT PHOTO: Coletti, et. al.

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