Browsing by Subject "Prestressed bridge girders"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    A Camber Study of MnDOT Prestressed Concrete I-Girders
    (Minnesota Department of Transportation, 1998-01) Woolf, Douglass; French, Catherine
    This project investigated the relationship between predicted and measured girder cambers. For more than three years, researchers collected camber data on girders of various depths and lengths from the time of strand release until shipment to the job site. Researchers used three camber prediction methods to compare with the measured values: PCI method, Branson's timestep approach, and "CRACK" analysis program by Ghali et. al. The Branson time-step approach resulted in the closest predictions to the measured cambers. The PCI method, although simple, gave reasonable long-term camber results compared with the more detailed methods.
  • Thumbnail Image
    Item
    Instrumentation and Fabrication of Two High-Strength Concrete Prestressed Bridge Girders
    (Minnesota Department of Transportation, 1998-01) Kielb, Jeffrey; French, Catherine E.; Leon, Roberto T.; Shield, Carol K.
    This report describes the design, instrumentation, construction, and test set-up of two high-strength concrete prestressed bridge girders. The girder specimens were constructed to evaluate prestress transfer length, prestress losses, flexural fatigue, ultimate flexural strength, and ultimate shear strength. Each test girder was a 132.75-foot long, 46-inch deep, Minnesota Department of Transportation (Mn/DOT) 45M girder section reinforced with 46 0.6-inch diameter 270 ksi prestressing strands. The 28-day nominal compressive strength of the girders was 10,500 psi. Each girder was made composite with a 9-inch thick, 48-inch wide composite concrete deck cast on top with a nominal compressive strength of 4000 psi. Girder I used a concrete mix incorporating crushed limestone aggregate while Girder II utilized round glacial gravel aggregate in the mix with the addition of microsilica. In addition, the two test girders incorporated two different end patterns of prestressing--draping versus a combination of draping and debonding--and two different stirrup configurations--standard Mn/DOT U versus a modified U with leg extensions. More than 200 strain gages were imbedded in each girder during construction. Other reports present flexural and shear testing results.
  • Thumbnail Image
    Item
    Self-Compacting Concrete (SCC) for Prestressed Bridge Girders
    (Minnesota Department of Transportation, 2008-10) Erkmen, Bulent; Shield, Carol K.; French, Catherine E.
    Researchers conducted an experimental program to investigate the viability of producing self-consolidating concrete (SCC) using locally available aggregate, and the viability of its use in the production of precast prestressed concrete bridge girders for the State of Minnesota. Six precast prestressed bridge girders were cast using four SCC and two conventional concrete mixes. Variations in the mixes included cementitious materials (ASTM Type I and III cement and Class C fly ash), natural gravel and crushed stone as coarse aggregate, and several admixtures. The girders were instrumented to monitor transfer length, camber, and prestress losses. In addition, companion cylinders were cast to measure the compressive strength and modulus of elasticity, and to monitor the creep and shrinkage over time. The viability of using several test methods to evaluate SCC fresh properties was also investigated. The test results indicated that the overall performance of the SCC girders was comparable to that of the conventional concrete girders. The measured, predicted, and calculated prestress losses were generally in good agreement. The study indicated that creep and shrinkage material models developed based on companion cylinder creep and shrinkage data can be used to reasonably predict measured prestress losses of both conventional and SCC prestressed bridge girders.