United States Department of Transportation
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Utilization of UHPC Bridge Superstructures in Texas— Volume 2: Structural Analysis, Design, and Full-Scale Testing of Precast, Pretensioned Girders
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2023-10-01
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[PDF-20.80 MB]
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Edition:Technical Report: September 2018–October 2022
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Abstract:The use of ultra-high performance concrete (UHPC) in Texas bridges has potential to produce substantial improvements to bridge construction. Advanced material properties and superior durability of UHPC can result in significant design and construction benefits. An analytical feasibility study showed that UHPC bridge girders provide increased design efficiency over conventional concrete (CC) girders, including reduced cross-sections, longer spans, and larger girder spacings. This study identified the desired material properties of nonproprietary UHPC for the fabrication of precast, pretensioned bridge girders with a CC deck slab. The characteristic material properties attained using the developed nonproprietary UHPC mixtures were used to design prototype bridge girders and full-scale Tx34 and Tx54 girder specimens with CC decks for laboratory testing. Three UHPC girder specimens were tested under the prototype design load demands to evaluate the girder response with respect to flexure, web shear, and interface shear. The fiber distribution and tensile strength impacted both the flexure and shear behavior. The flexure and shear performance were enhanced relative to CC girders. During flexure testing, no cracking was observed up to factored moment demands. The moment applied to each girder was 30–50 percent higher than the corresponding design-factored moment. The use of harped strands and minimum transverse reinforcement also enhanced the shear performance. The Tx34 girder with straight strands had a lower tensile strength, and the applied shear was slightly below the design-factored shear at the unreinforced end. For all other girder ends, the experimental shear capacity was at least twice the design-factored shear demand. Mild steel reinforcement in the shape of U-bars at the interface of the CC-UHPC composite section effectively transferred shear up to the design-factored loads with negligible slip, although some limited slip was observed at loads exceeding factored load demands. The selected prediction models and the recommended design approach provided results consistent with the measured behavior.
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