United States Department of Transportation
i
Bridge Girder Alternatives for Extremely Aggressive Environments
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2018-01-31
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[PDF-12.99 MB]
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TRIS Online Accession Number:01677317
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Edition:Final Report
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Abstract:The primary objective of this study was to identify viable alternatives for fiber-reinforced polymer (FRP) bridge girders and evaluate their potential for use in extremely aggressive environments in Florida. The first phase of the study included a comprehensive survey of in-service FRP-girder bridges in the U.S. along with several projects in Europe. Four distinct girder types were identified ((1) pultruded sections, (2) U-girders, (3) concrete-filled FRP tubes, and (4) Hillman Composite Beams (HCBs)) and the current status of existing bridges for each type was verified. Fiber-reinforced polymer flat-panel slab bridges were also investigated. Three general girder geometries were chosen for further investigation and evaluation: (1) hybrid FRP/concrete-filled U-girder, (2) hybrid FRP/concrete-filled tube, and a (3) pultruded double-web Ibeam (DWB). Tthe required amount of FRP material and associated manufacturing costs were determined for a range of span lengths between 30 ft and 75 ft. All three options were assumed to develop full composite action with an 8-in-thick cast-in-place reinforced concrete deck. The number of girders per span was also treated as a variable. Two unique design methodologies were investigated for the FRP U-girders. The first method relied on AASHTO distribution factors to determine the single-girder structural demand. The second method involved finite element analysis of the entire bridge combined with structural optimization techniques to determine the most efficient girder geometry. The CFFTs were exclusively using the AASHTO distribution factor method, and the DWB alternative was evaluated using finite element analysis. Results indicate that the hybrid FRP/concrete U-girder is the most efficient and cost-effective alternative. The girder cost per square foot for the U-girder alternative ranges from just over $40 per square foot of bridge deck for a 30-ft span to $140 per square foot for the 75-ft span. These estimates include the costs for materials and manufacturing of the FRP U-girder and the cast-in-place concrete required to fill the girder on-site. Additional costs associated with placing the girders and the cast-in-place reinforced concrete deck are not included.
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