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Innovative Jakway Bridge nominated for quality award
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| The new Jakway Park Bridge |
AURORA - The new Jakway Park Bridge in Buchanan County can certainly be called “Innovative”. It could be this innovative style that got the bridge nominated as an Iowa Quality Initiative Structures Award contestant.
It is the first highway bridge in North America to be built with a new generation of Ultra-High Performance Concrete (UHPC) pi-girders, the first North American highway bridge project to incorporate batching of UHPC in a ready-mix truck, and the second highway bridge project in Iowa and North America to be built with UHPC girders -- providing another, significant step towards “The Bridge of the Future.”
Buchanan County was granted funding for this project through the TEA-21 Innovative Bridge Construction Program (IBRC), managed by the Federal Highway Administration (FHWA) to construct a highway bridge using an optimized pi-girder section with (UHPC).
The Office of Bridges and Structures at the Iowa Department of Transportation and the Bridge Engineering Center at Iowa State University designed the bridge; a combination of cast-in-place, simple span slabs with a center span consisting of a series of precast UHPC pi-shaped girders.
The bridge is 24 ‘ 3 “ wide by 112’ 4” long. The UHPC center span is 51’ 2”
THE MATERIAL
Developed in France during the 1990s, UHPC has seen limited use in North American bridge projects. Consisting of fine sand, cement, and silica fume in a dense, low water-cement ratio mix, this highly moldable material offers a combination of superior properties including compressive strengths up to 30,000 psi and flexural strengths up to 6,000 psi, ductility, durability and a vast range of aesthetic design possibilities.
UHPC is denser than conventional concrete which attributes to its remarkable imperviousness and durability. In addition, UHPC is extremely low in permeability and performs better in terms of abrasion and chemical resistance, freeze-thaw, carbonation and chloride ion penetration (less than 0.5 mm). To improve ductility, steel or polyvinyl alcohol (PVA) fibers are added, replacing the need for passive mild reinforcing steel.
INNOVATION
As mentioned, this project is innovative for a number of reasons, including: the second use of UHPC in a highway bridge structure; introduction of a new UHPC batching procedure and; the first highway bridge to be built with a new generation of UHPC pi-girders (in a monolithic structure). This project has provided an excellent opportunity to learn about the design, testing, mixing and casting methods involving UHPC. Additional, future research will address current design and production concerns and develop more efficient beam designs to maximize UHPC’s unique structural properties.
COMPLEXITY OF THE PROJECT
This project had several complex challenges to overcome, some that impacted the design process.
Testing of the section by Turner-Fairbank had validated the FEM analysis and first generation geometry for flexural and shear capacity in the longitudinal direction. The testing also confirmed that the stress in the transverse direction of the deck were unacceptable for service loading and a low transverse, live load distribution between adjacent pi-girders would require stiffening. These two issues were the biggest design challenges and drove the eventual development of the second generation pi-girder.
On the north side of the road is a County park named Jakway Park. The property was acquired using 4F federal funds. In order to avoid extensive delays, we were required to design the bridge without acquiring an additional right-of-way to the north; otherwise clearances would be required from Washington, DC.
Because the existing, historical bridge was built in 1910, a required review had been done previously. As we began the design process however, an archaeological dig also began adjacent to the project location; the site of a village that existed in the 1840’s and 1850’s. The village was originally plotted as “Buchanan” but referred to as “Mudville” (listed in the National Register of Historic Places.) Fortunately, we were able to work directly with the archaeologists and obtain clearance on the area essential for construction of the new bridge.
The unique properties and relative newness of the material also impacted the project’s complexity. Its costs are high, therefore the need to limit the quantity of material was an essential economic consideration. This led to a special, customized design that permitted the superstructure and deck to be part cast-in-place and part precast.
Fabricators across the United States avoided the project because of lack of experience with UHPC and tight schedules. This resulted in the beams being fabricated at Lafarge’s precast facility in Winnipeg, Canada, due to their prior, proven expertise with the material for another Iowa bridge project. (They produced three 110 ft. UHPC beams for the Wapello County-Mars Hill bridge in 2005.) In addition, the Iowa Department of Transportation has no inspectors in the area therefore travel to Winnipeg was necessary for inspection of the beams.
TIMELINESS
Complexities to do with beam fabrication caused some delays that pushed the project into the fall of 2008, which also raised weather and scheduling concerns. However, fifty-five days were assigned to the project and, in the end, fifty-two days were utilized. The bridge opened to traffic on November 26,2008, and an official ribbon cutting event will take place in the spring of 2009.
COOPERATION
Cooperation between all parties involved was outstanding. The time and attention that everyone exerted is clearly visible in the finished product where construction proceeded flawlessly. Furthermore, this important, collaborative project has allowed Buchanan County, the FHWA, the Iowa Department of Transportation, the Bridge Engineering Center at Iowa State University and Lafarge the opportunity to gain valuable experience in the designing, testing, mixing, and casting of UHPC in this “first ever” use of the material for an innovative, new generation pi-girder. By using the modified optimized section, the project team hopes to take better advantage of the unique properties of UHPC and help reduce the cost of using it in future projects.
SAFETY
No accidents were reported during the construction of this project. Safety is always priority on all IDOT construction projects. Use of personal protective equipment (PPE) was mandatory and proper procedures were followed with handling of heavy equipment and installation of bridge elements. For visitors, extra measures were taken to ensure their safety as well, with the creation and staging of specific, designated visitor areas. In addition, off site girder production at the precast plant required rigid adherence to the company’s own safety procedures – by workers, visitors and inspectors.
GENERAL APPEARANCE AND WORKMANSHIP
The Jakway Park Bridge has a clean, balanced and symmetrical appearance. The profile is attractive and somewhat unique due to the nature of the approach slab sections meeting the precast pi-girder sections. Bearing in mind the many challenges that this project presented, the workmanship has not been sacrificed and all components have been produced with quality results. This new bridge has superior durability and strength qualities that will relate to several decades of usable service, with very little maintenance required. It can certainly be considered an important technological advancement by many experts in the bridge building industry.
It is the first highway bridge in North America to be built with a new generation of Ultra-High Performance Concrete (UHPC) pi-girders, the first North American highway bridge project to incorporate batching of UHPC in a ready-mix truck, and the second highway bridge project in Iowa and North America to be built with UHPC girders -- providing another, significant step towards “The Bridge of the Future.”
Buchanan County was granted funding for this project through the TEA-21 Innovative Bridge Construction Program (IBRC), managed by the Federal Highway Administration (FHWA) to construct a highway bridge using an optimized pi-girder section with (UHPC).
The Office of Bridges and Structures at the Iowa Department of Transportation and the Bridge Engineering Center at Iowa State University designed the bridge; a combination of cast-in-place, simple span slabs with a center span consisting of a series of precast UHPC pi-shaped girders.
The bridge is 24 ‘ 3 “ wide by 112’ 4” long. The UHPC center span is 51’ 2”
THE MATERIAL
Developed in France during the 1990s, UHPC has seen limited use in North American bridge projects. Consisting of fine sand, cement, and silica fume in a dense, low water-cement ratio mix, this highly moldable material offers a combination of superior properties including compressive strengths up to 30,000 psi and flexural strengths up to 6,000 psi, ductility, durability and a vast range of aesthetic design possibilities.
UHPC is denser than conventional concrete which attributes to its remarkable imperviousness and durability. In addition, UHPC is extremely low in permeability and performs better in terms of abrasion and chemical resistance, freeze-thaw, carbonation and chloride ion penetration (less than 0.5 mm). To improve ductility, steel or polyvinyl alcohol (PVA) fibers are added, replacing the need for passive mild reinforcing steel.
INNOVATION
As mentioned, this project is innovative for a number of reasons, including: the second use of UHPC in a highway bridge structure; introduction of a new UHPC batching procedure and; the first highway bridge to be built with a new generation of UHPC pi-girders (in a monolithic structure). This project has provided an excellent opportunity to learn about the design, testing, mixing and casting methods involving UHPC. Additional, future research will address current design and production concerns and develop more efficient beam designs to maximize UHPC’s unique structural properties.
COMPLEXITY OF THE PROJECT
This project had several complex challenges to overcome, some that impacted the design process.
Testing of the section by Turner-Fairbank had validated the FEM analysis and first generation geometry for flexural and shear capacity in the longitudinal direction. The testing also confirmed that the stress in the transverse direction of the deck were unacceptable for service loading and a low transverse, live load distribution between adjacent pi-girders would require stiffening. These two issues were the biggest design challenges and drove the eventual development of the second generation pi-girder.
On the north side of the road is a County park named Jakway Park. The property was acquired using 4F federal funds. In order to avoid extensive delays, we were required to design the bridge without acquiring an additional right-of-way to the north; otherwise clearances would be required from Washington, DC.
Because the existing, historical bridge was built in 1910, a required review had been done previously. As we began the design process however, an archaeological dig also began adjacent to the project location; the site of a village that existed in the 1840’s and 1850’s. The village was originally plotted as “Buchanan” but referred to as “Mudville” (listed in the National Register of Historic Places.) Fortunately, we were able to work directly with the archaeologists and obtain clearance on the area essential for construction of the new bridge.
The unique properties and relative newness of the material also impacted the project’s complexity. Its costs are high, therefore the need to limit the quantity of material was an essential economic consideration. This led to a special, customized design that permitted the superstructure and deck to be part cast-in-place and part precast.
Fabricators across the United States avoided the project because of lack of experience with UHPC and tight schedules. This resulted in the beams being fabricated at Lafarge’s precast facility in Winnipeg, Canada, due to their prior, proven expertise with the material for another Iowa bridge project. (They produced three 110 ft. UHPC beams for the Wapello County-Mars Hill bridge in 2005.) In addition, the Iowa Department of Transportation has no inspectors in the area therefore travel to Winnipeg was necessary for inspection of the beams.
TIMELINESS
Complexities to do with beam fabrication caused some delays that pushed the project into the fall of 2008, which also raised weather and scheduling concerns. However, fifty-five days were assigned to the project and, in the end, fifty-two days were utilized. The bridge opened to traffic on November 26,2008, and an official ribbon cutting event will take place in the spring of 2009.
COOPERATION
Cooperation between all parties involved was outstanding. The time and attention that everyone exerted is clearly visible in the finished product where construction proceeded flawlessly. Furthermore, this important, collaborative project has allowed Buchanan County, the FHWA, the Iowa Department of Transportation, the Bridge Engineering Center at Iowa State University and Lafarge the opportunity to gain valuable experience in the designing, testing, mixing, and casting of UHPC in this “first ever” use of the material for an innovative, new generation pi-girder. By using the modified optimized section, the project team hopes to take better advantage of the unique properties of UHPC and help reduce the cost of using it in future projects.
SAFETY
No accidents were reported during the construction of this project. Safety is always priority on all IDOT construction projects. Use of personal protective equipment (PPE) was mandatory and proper procedures were followed with handling of heavy equipment and installation of bridge elements. For visitors, extra measures were taken to ensure their safety as well, with the creation and staging of specific, designated visitor areas. In addition, off site girder production at the precast plant required rigid adherence to the company’s own safety procedures – by workers, visitors and inspectors.
GENERAL APPEARANCE AND WORKMANSHIP
The Jakway Park Bridge has a clean, balanced and symmetrical appearance. The profile is attractive and somewhat unique due to the nature of the approach slab sections meeting the precast pi-girder sections. Bearing in mind the many challenges that this project presented, the workmanship has not been sacrificed and all components have been produced with quality results. This new bridge has superior durability and strength qualities that will relate to several decades of usable service, with very little maintenance required. It can certainly be considered an important technological advancement by many experts in the bridge building industry.
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Reader Comments
The following are comments from the readers. In no way do they represent the view of communitynewspapergroup.com.
John Bower wrote on Dec 30, 2008 12:22 PM:
" I'm not sure what a pi-girder is, but I assume it's what has been termed a double-tee girder, where the precast girder flange is cast with two tee stems. "
John D wrote on Jan 6, 2009 4:08 PM:
" As publisher of Aspire - The Concrete Bridge Magazine (www.aspirebridge.org), I have been very impressed with the innovation shown by the Buchanan County engineer. It is encouraging to see local government working hand-in-hand with the state agency, the state university and the Federal Highway Administration to bring leading international technology to those in rural America. Taking advantage of federal demonstration funding opportunities makes this cost-effective. It also allows the appropriateness of this technology to be verified in yet another application. Too often, state and local ageny employees don't receive the appreciation they deserve. Cudos to the Buchanan County commissioners and engineering staff! "
Paul wrote on Dec 30, 2008 12:16 PM: