Recently completed under budget and three months ahead of schedule, the High Road Bridge over Long Run Creek in Lockport Township, Ill., is the first
Recently completed under budget and three months ahead of schedule, the High Road Bridge over Long Run Creek in Lockport Township, Ill., is the first permanent highway installation featuring hybrid-composite beams (HCB). HC Bridge Co., LLC developed the structural members as a solution offering both accelerated bridge construction and enhanced durability.
Functionally obsolete and structurally deficient, the former High Road Bridge Û dating from 1935 Û had outlived its usefulness. Among the narrow structure’s pitfalls were exposed and dangling primary reinforcing bars. Accordingly, a replacement structure was designed by Teng & Associates, Inc. of Chicago, whose engineers chose to incorporate HCB, a new type of bridge technology that provides extended service life with minimal or no maintenance to girders.
HCBs comprise three main subcomponents: a fiber reinforced plastic (FRP) shell, compression reinforcement, and tension reinforcement. Compression reinforcement is achieved by pumping self-consolidating concrete (SCC) into an arch conduit within the beam shell. Tension reinforcement is provided by high-strength steel prestressing strands that run along the shell’s bottom flanges. All components are encapsulated in an FRP shell to protect the beam from salt corrosion and provide additional structural capacity.
OPEN TO TRAFFIC
The superstructure for the 57-ft., single-span High Road Bridge includes six 42-in.-deep HCBs spaced at 7-ft. 4-in. centers, supporting a conventional 8-in.-thick reinforced concrete deck. Despite the use of an innovative framing system, reports HC Bridge President John Hillman, construction was the same as that required for traditional concrete or steel bridges. The HCB was designed to make every detail interchangeable with conventional bridge technology, he emphasizes, so it works for building new structures, as well as widening existing bridges and reconstructing older spans where abutments are viable.
According to Hillman, HC Bridge also developed a shear transfer mechanism to secure the concrete deck and exploit composite action between the HCBs and concrete slab: a series of conventional steel reinforcement bars with 90 degree hooks at both ends serve as shear connectors, placed on a 45-degree angle and embedded in the HCB arch on one end and the concrete deck at the other. Thus, an efficient transfer of shear occurs as the connectors’ diagonal orientation allows them to function more like a truss element in tension than a headed stud in shear. Further, the connectors are hot-dipped galvanized for extended service life.
Produced by Harbor Technologies, Inc., of Brunswick, Maine, the HCBs Û approximately one-tenth the weight of a typical precast beam of equal length Û effectively slashed the project’s shipping and erection costs. All bridge beams were transported on one truck, rather than six trucks that would have been necessary for alternate materials; and, erection required only a 30-ton crane, as compared to the 150- to 200-ton crane needed for precast units. Moreover, the six beams were set in merely 90 minutes. Herlihy Mid-Continent Co. of Romeoville, Ill., performed the bridge construction.
Herlihy Senior Project Manager Art Haggerty observes that the composite beams worked well with the flow of the project. We were able to set the beams easily in conjunction with the rest of our work, he recalls. 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.
BRIDGE TO THE FUTURE
Viewing HCBs as stronger, lighter and more corrosion-resistant than traditional concrete or steel beams, thus providing real advantages to the Highway Department, Lockport Township Highway Commissioner Jack Waxweiler worked with the Illinois Department of Transportation to secure a $250,000 award grant from the Federal Highway Administration (FHWA) through the Innovative Bridge Research and Design (IBRD) program. The IBRD provides discretionary funding to local government agencies to help advance innovation in bridge infrastructure technologies nationwide.
Prior to installation in the field, HCBs designed and fabricated for High Road Bridge underwent extensive testing as part of the IBRD program at the Advanced Engineered Wood and Composite (AEWC) Center at University of Maine, Orono. A prototype HCB was subjected to half a million cycles of fatigue loading, then submitted to 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 hydraulic ram’s maximum capacity (290,000 lb. or 4.4 times the bridge design load), the HCB remained elastic and did not fail.
Although High Road Bridge is the first HCB highway installation, the technology has undergone extensive testing and development during the last 12 years. The first live-load test of a full-scale HCB bridge was conducted in November 2007 at the Transportation Technology Center, Inc. (TTCI) near Pueblo, Colo. At that time, a prototype HCB railroad span was subjected to a battery of tests involving a full-size locomotive pulling 26 heavy-axle coal cars transporting loads approximately seven times as heavy as design loads for the High Road Bridge. More recently, the Association of American Railroads began endurance testing in October at TTCI, after carefully assessing data from the earlier research.
Illinois State Bridge Engineer Ralph Anderson notes that Illinois is interested in expanding the use of the hybrid composite beams for future bridge projects. Illinois, like most states, has hundreds of short-span bridges that will need replacement in the near future, he asserts.
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, confirms Teng & Associates Vice President Transportation Byron 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. Û www.hcbridge.net