When a state department of transportation planned for a successor to a 90-year old bridge along U.S. Highway 30, the stars aligned for precast concrete methods—in lieu of much structural steel and cast-in-place concrete. Replacement of the U.S. 30 bridge at the Burnt River and Union Pacific Rail Road (UPRR) line in eastern Oregon was accompanied by precast-friendly factors: a remote location in a market served by three Precast/Prestressed Concrete Institute-certified plants; department of transportation keen on the economy and engineering efficacy of prestressed bulb tee girders in the 150-foot-plus class; and, Federal Highway Administration funding mechanism compelling a state’s inaugural precast deck panel project.
U.S. 30 @ Burnt River Bridge, 1.0 and 2.0. Shown in 1926 in an Oregon Department of Transportation archive image, the original structure served U.S. 30 motorists well into a phase of FHWA-defined functional obsolescence. Paralleling Interstate 84 in eastern Oregon, the route is lightly traveled. The new, nearly all-precast crossing has a projected 75-year service life.
Nearly a year in service, the new Burnt River and UPRR bridge along U.S. 30 in Baker County is precast manifest: four 162-ft. prestressed bulb-tee girders supporting a two-lane roadway plus shoulders; 15 full-width deck panels, 32- x 8-ft.; and, an abutment with 465 mechanically stabilized earth panels totaling 9,500 sq. ft. Hamilton Construction Co. of Springfield, Ore., landed the project with a low bid of $2.35 million.
The new structure’s 90-in. deep girders are a bulb-tee profile the Oregon Department of Transportation has embraced for span and depth efficiency, plus optimal prestressing strand concentration. The state’s leader in precast/prestressed girders, Knife River Corp. Northwest, developed the BT90 in 2005, presenting it to ODOT and Hamilton Construction for a UPRR crossing. The U.S. 97, Mt. Hood to Chemult, structure required 183-ft. single-piece bulb tees, a length threshold Washington State Department of Transportation had established and since exceeded. The new section exceeded current ODOT capabilities of the 84-in. bulb tee girder by 20 feet.
Hamilton Construction, David Evans & Associates, and ODOT approved Knife River NW’s BT90 as part of its design/build contract, erecting seven of the super girders. The U.S. 97/UPRR structure set a new length record for (trailered) precast/prestressed bulb tee members on an ODOT project, and Knife River NW has since fabricated 400 BT90s in the 160- to 185-ft. range.
“The BT90 span capabilities combined with improved shipping equipment has expanded our market share when compared to structural steel and cast-in-place alternatives.” says Knife River NW Chief Engineer Keith Kaufman, P.E., Ph.D. “We worked with the design build team and ODOT to develop the cross section and figured demand would follow once a few projects proved the economy and delivery feasibility of the super girders.”
The BT90 enjoyed a solid track record with Hamilton Construction and ODOT leading into the U.S. 30/Burnt River bridge replacement. The project was an in-house ODOT design, with abutment engineering assistance from Reinforced Earth Co., Western Division, Denver. Knife River NW fabricated the deck panels, along with the super girders, at its Harrisburg, Ore., operation. Freedom Precast produced the Reinforced Earth Cruciform MSE panels in Springfield, Ore.
The bridge abutment is located on the northwest side of a roadway realigned with slightly more skew to the rail line than its predecessor. Superstructure loads are distributed across a cast-in-place girder seat, steel H piles driven to bedrock, 9,300 yd. of abutment fill, and the MSE panels. ODOT elected to expand an existing abutment as a means of eliminating the original structure’s second span. Construction of a pier was subject to environmental impact review owing to a waterway that resembles more of creek than a river at U.S. 30. The BT90 girders enabled a single span meeting UPRR vertical and ground clearance requirements.
Roadway realignment, abutment expansion and a switch from the original replacement bridge design—two spans with 120-ft. prestressed girders—afforded ODOT and Hamilton Construction ample savings to cover shipping and additional crane costs associated with the precast concrete specs. The new structure succeeds a bridge completed in 1922, with main steel through-truss span and cast-in-place, reinforced concrete deck girder approach span.
The U.S. 30/Burnt River bridge lies between two Interstate 84 interchanges; closure meant a seven-mile detour. The limited traffic disruption factor, lower potential for schedule delays attributable to the precast girders and MSE panels, plus relatively simple construction scheme, spelled a good opportunity to test precast deck panels.
That specification and proposed use of ultra high performance mixes for cast-in-place connections, in turn, helped garner a $500,000 FHWA program grant, according to ODOT Region 5 Tech Center’s George Bornstedt, P.E., interim Bridge-Environmental–Geo-Hydro manager.
“Initially we were going to use a cast in place deck, but then identified the opportunity for a Highways for LIFE demonstration,” he says. “We added a section on precast deck panels to the department bridge manual, based on AASTHTO code, and have approved them for a current project.” (Knife River NW is casting the panels and prestressed girders for that job, Oregon Highway 58, with two bridges each in 2013 and 2014).
FHWA notes that the purpose of its Highways for LIFE (HfL) funding program is to advance Longer-lasting highway infrastructure using Innovations to accomplish the Fast construction of Efficient and safe highways and bridges. Innovations span technologies, materials, tools, equipment, procedures, specifications, methodologies, processes or practices used in the financing, design or construction of highways. The program is focused on accelerating their adoption in the highway community—a departure from federal and state transportation agencies’ past tendency to embrace innovations over decades versus years.
Agency officials underscore these goals for HfL candidate projects: a) improve safety during and after construction; b) reduce congestion caused by construction, and c) improve the quality of the highway infrastructure. The legislative directive behind HfL represents a change strategy, they add, as it contains elements to create awareness, inform, educate, train, assist and entice State DOTs and their staff. Funding for projects is an enticement, but it is only one of the elements. HfL also intends to provide the training and technical assistance necessary to ease and sustain the innovation adoption.
20,000 PSI Performance Mix
Highway U.S. 30 crosses the Burnt River between two Interstate 84 interchanges, about 30 miles north of Ontario, Oregon, and near the Idaho border. Hamilton Construction enlisted Clearwater Concrete to deliver 600 yd. of ready mixed from a nearby plant, to cast footings, girder haunches, new approach pavement, deck wear course, and filling a limestone cavern near foundation supports.
A small but significant cast-in-place concrete specification rounds out the Burnt River Bridge concrete schedule: 22 cubic yards of JS1000 Joint Fill, one of Lafarge North America’s Ductal ultra-high performance concrete (UHPC) mixes. The JS1000 connects deck panels, girders and haunches. Lafarge supplied the UHPC premix in 1-ton supersacks; twin, 0.665-yd. mixers for on-site production; and, an engineer from Lafarge Canada, whose offices in Calgary and Toronto oversee the Ductal market development and support on both sides of the border.
Lafarge’s engineering and technical team offers a range of services from conception through to completion, typically including a preconstruction meeting with the contractor; scheduling; supply of mixers and testing equipment; and, site supervision during the batching and placing of all Ductal materials. Quality assurance and quality control testing and reporting are also provided for the project owner.
Lafarge promotes Ductal Joint Fill as a field-cast UHPC connection solution for superior strength, durability, fluidity and increased bond capacity in precast bridge elements. Its steel fiber matrix is significantly stronger than conventional concrete and performs better in terms of fatigue, abrasion and chemical resistance, freeze-thaw, carbonation and chloride ion penetration. Additionally, because of its optimized gradation of the raw material components, UHPC is denser than conventional concrete. This feature, along with nanometer sized, non-connected pores throughout its cementitious matrix, impart imperviousness and durability against adverse conditions or aggressive agents.
When JS1000 is used with precast deck panels, precast box girders or bulb-tee girder joints, fabrication and installation processes are simplified, full deck continuity is achieved and the bridge deck joint is no longer the weakest link, Lafarge engineers affirm.
Lafarge began JS1000 commercialization in 2004, initially through collaboration with the Ministry of Transportation of Ontario (MTO). The first field application involved a bridge at Rainy Lake over the Canadian National Railway line in 2006. MTO has led North American transportation agencies in Ductal Joint Fill applications since, followed by the New York State Department of Transportation.
In North America, the JS1000 business has become self-perpetuating, Lafarge officials note, indicating an opportunity for enormous growth. In 2010, five bridges were completed with the product. In the summer of 2013, thirty-six projects were slated for completion by year-end. With projects now completed in Ontario, New York, Iowa, Montana, Massachusetts and Oregon, acceptance is increasing at a rapid pace. By the end of 2014, it is expected that Ductal Joint Fill projects will also be completed in Ohio, Pennsylvania, Manitoba, Nebraska, New Jersey, Utah and South Carolina.
FHWA measures growth of Ultra-High Performance Concrete
Adapted from the Federal Highway Administration’s September 2013 Focus e-newsletter… A new report summarizes UHPC research, development, and deployment efforts around the world. Ultra-High Performance Concrete: A State-of-the-Art Report for the Bridge Community (Pub. No. FHWAHRT-13-060) includes details on materials and production; mechanical properties; structural design and testing; and, durability measurement.
“This information allows State and local transportation agencies, researchers, and others to deepen their understanding of UHPC and the opportunities it offers to accelerate bridge construction,” affirms FHWA’s Ben Graybeal, who co-authored the report with Glenview, Ill., engineering consultant Henry Russell.
UHPC is an advanced cementitious composite material developed in the 1990s and commercially available in the United States since 2000. It is typically acquired from a supplier in three separate components: pre-bagged cementitious powder, steel fibers, and chemical admixtures. Water completes the mixture. The UHPC is then placed into the formwork using standard construction equipment.
The FHWA began investigating UHPC for highway infrastructure use in 2001 and has worked with State transportation departments to deploy the technology since 2002. Bridge applications have included using UHPC for precast/prestressed girders; precast waffle panels for bridge decks; and, as a field-cast material joining precast concrete deck panels, girders, and adjacent girder flanges.
Compared to conventional concrete materials, Graybeal and Russell contend, UHPC exhibits superior properties such as exceptional durability, ductility, high compressive and flexural strengths, and long-term stability. It generally contains high cementitious materials, low water-to-cement material ratios, compressive strengths above 21,000 psi (150 MPa), and sustained tensile strength resulting from internal fiber reinforcement.
These advanced properties have been used to develop new structural forms that facilitate accelerated bridge construction. While UHPC has higher initial costs than conventional concrete, bridges with UHPC components are expected to have a longer service life and require less maintenance than conventional structures.
The new FHWA report highlights projects in the United States, Canada, Europe, Asia, and Australia—among 90-plus UHPC bridges in service worldwide. The first domestic highway structure to use UHPC was the Mars Hill Bridge in Wapello County, Iowa (2006)—a simple, single-span structure with precast/prestressed girders and cast-in-place deck. Subsequent projects in Iowa have included the Little Cedar Creek bridge (2011), the world’s first structure to feature a precast, full-depth UHPC waffle-deck panel system connected with field-cast UHPC joints. Ultimately, the material’s mechanical and durability properties allowed the construction of a resilient, lightweight deck system that was completed in about 70 percent of the time compared to a similar design using conventional concrete mix.
The new UHPC connection details eliminate conflict points between the reinforcing bars and discrete connectors, allowing for easy field assembly. Buy America provisions are relevant to the steel fiber reinforcement used in UHPC. States that are planning to use UHPC in projects should work with their FHWA division office early in the design process to determine the availability of a domestic manufacturer.
“There are strong indications that a proven class of steel fibers will be domestically produced and available by the end of 2013,” says Graybeal.
While highlighting UHPC projects to date, the report also examines the future direction of the technology and current challenges to achieving wide-scale implementation in the United States. These include the need for more demonstration projects, cost-benefit studies, and a new design and production document based on the American Association of State Highway and Transportation Officials’ Load and Resistance Factor Design BridgeDesign Specifications and the AASHTO LRFD Bridge Construction Specifications.