HC Bridge Maine LLC, a company specializing in the development of hybrid-composite structural alternatives that can be used for accelerated bridge construction and offer a long service life, recently announced that construction has been completed on the High Road Bridge over Long Run Creek in Lockport Township, Ill., three months ahead of schedule.
The innovative structure, now open to traffic at High Road, is the first permanent highway installation of hybrid-composite beams (HCBs), developed by the HC Bridge Co. LLC.
The existing High Road Bridge, constructed in 1935, had outlived its useful service life and was categorized as both structurally deficient and functionally obsolete. Not only was the existing bridge very narrow, but most of the main reinforcing bars on the bottom side of the structure were exposed and in some cases dangling from the bottom of the bridge. In order to reduce future maintenance costs, the replacement structure, designed by Teng & Associates Inc. of Chicago, utilized a new type of bridge technology—HCB—that provides an extended service life with minimal or no maintenance to the bridge girders.
HCBs are composed of three main subcomponents: a fiber-reinforced polymer shell, compression reinforcement and tension reinforcement. The compression reinforcement consists of concrete that is pumped into an arch conduit within the beam shell. The tension reinforcement consists of high-strength steel prestressing strands that run along the bottom flanges of the beam shell. All of this is encapsulated in a fiber-reinforced plastic shell protecting the beam from salt corrosion and providing added structural capacity.
Byron Danley, vice president of transportation for Teng & Associates, stated that they are always looking for innovative solutions to the problems facing their clients.
“As our infrastructure ages and our nation’s bridges are rapidly deteriorating, the hybrid-composite beams provide a good alternative to traditional beams (steel or concrete) at a lower initial and life-cycle cost due to their durability and corrosion resistance,” said Danley. “The best route to reducing the growing backlog of deteriorated bridges is to embrace new technologies like HCBs that provide longer lives for new bridges.”
The superstructure for this 57-ft single-span bridge is composed of six 42-in.-deep HCBs spaced at 7-ft 4-in. centers, supporting a conventional 8-in.-thick reinforced concrete deck. According to John Hillman, president of HC Bridge, despite the use of the innovative framing system, the bridge was constructed exactly the same way as a conventional concrete or steel bridge. Careful attention was paid in the development of the HCB to make every detail interchangeable with conventional bridge technology. By doing this, the HCB not only works for new construction, but can be used to widen existing bridges as well as reconstruction of older bridges where existing abutments can be reused.
According to Hillman, in order to secure the concrete deck and exploit composite action between the HCBs and the concrete slab, HC Bridge also developed a shear transfer mechanism composed of a series of conventional steel reinforcement bars with 90° hooks at both ends. These “shear connectors” are placed on a 45° angle and embedded in the HCB arch on one end and the concrete deck at the other end, providing an efficient transfer of shear as the diagonal orientation of the connector allows it to function more like a truss element in tension rather than a headed stud in shear. The connectors are hot-dipped galvanized to provide for extended service life of this component.
Strength built in
The HCBs are inherently stronger, lighter and more corrosion-resistant than the traditional concrete or steel beams, providing real advantages to the Lockport Township Highway Department. Manufactured by Harbor Technologies Inc. of Brunswick, Maine, the HCBs weigh approximately one-tenth of what a typical precast concrete beam weighs for the same span length. This lighter weight reduced shipping and erection costs. As a result, all of the beams for the bridge were shipped on one truck instead of what would have taken six trucks using competing methods, and they were erected using a 30-ton crane instead of the large 150-200-ton crane that would have been required for precast concrete beams. Construction of the High Road Bridge was conducted by Herlihy Mid-Continent Co. of Romeoville, Ill.
In an effort to help promote this new type of technology, Lockport Township Highway Commissioner Jack Waxweiler worked with the Illinois Department of Transportation to secure a $250,000 grant from the Federal Highway Administration (FHWA) through the Innovative Bridge Research and Design (IBRD) Program. Established by FHWA, IBRD provides discretionary funding to local government agencies to help facilitate innovation in advancing the technology for construction of our nation’s bridge infrastructure.
As part of the IBRD program and prior to installation in the High Road Bridge, the HCBs designed and constructed for the High Road Bridge underwent extensive testing at the Advanced Engineered Wood and Composite (AEWC) Center at the University of Maine, located in Orono. A prototype HCB was subjected to half a million cycles of fatigue loading prior to being loaded to the code-specified factored loads for both bending and shear. After maintaining perfectly linear elastic behavior under these loadings, an attempt was made to load the beam to failure. Even at the maximum capacity of the hydraulic ram, which was 290,000 lb, or 4.4 times the bridge design load, the HCB remained linear elastic and did not fail. According to Robert Lindyberg, P.E., assistant director for Boatbuilding and Composites University of Maine AEWC Center, these tests validated the strength set forth by the Illinois Department of Transportation.
“The success of this project validated the innovative nature of the product itself and its performance,” said Lindyberg. “As a result, HCBs are now being considered for bridges in Maine.”
Waxweiler stated that the project was extremely efficient.
“The beams worked out really well,” he said. “It only took 90 minutes to set six beams. For traditional steel beams, this erection process would have taken a lot longer and required the use of heavier equipment. Instead, the HCBs arrived in one truck, which is much more economical. The bridge construction finished ahead of schedule, and the HCBs are certainly part of this success.”
Looking ahead
Waxweiler also noted that he is confident that HCB technology will reduce the necessary maintenance and repair he sees with other bridges.
According to Art Haggerty, senior project manager for Herlihy Mid-Continent, the lightweight nature of the beams worked well with the flow of the project. The crew was able to use a small hydraulic picker to set the beams, eliminating the need to bring in a large crane for the sole purpose of setting traditionally heavier beams.
“We were able to set the beams easily in conjunction with the rest of our work,” Haggerty said. “At first, we had reservations about attaching our bridge deck forming system to the smooth gel-coat-finished exterior of the hybrid beams. Also, we were unsure of how the hybrid beams would react when concrete was poured loading the overhangs. However, the beams’ tough exterior and rigid construction accepted our standard deck forming system with very little trouble, and the deck pour resulted in deflections well within acceptable limits.”
Haggerty added that Herlihy prides itself on bringing ingenuity into projects, and they are confident that the HCB technology has advanced the state of bridge construction.
“This project demonstrates the constructability of this technology,” he said. “This project was a big success, resulting in a high-quality bridge that was finished under budget and ahead of schedule.”
Ralph Anderson, Illinois state bridge engineer, said that Illinois is very interested in expanding the use of the HCBs for future bridge projects.
“Illinois, like most states, has hundreds of short-span bridges that will need replacement in the near future,” said Anderson. “I expect this technology will provide an economical option that will greatly benefit the citizens of Illinois.”
Although this is the first highway installation of the HCBs, the technology has undergone extensive testing and development during the past 12 years. The first live-load test of a full-scale HCB bridge was conducted at the Transportation Technology Center Inc. (TTCI) near Pueblo, Colo., in November 2007. During these tests, a prototype HCB bridge was subjected to a battery of tests consisting of a full-size locomotive pulling 26 heavy-axle load coal cars. The loads used in the railroad bridge were approximately seven times as heavy as the design loads for the High Road Bridge. After carefully studying the data collected from these tests, the Association of American Railroads is in the process of conducting endurance testing at TTCI. The testing began in October.
