Impact of overhang construction on girder design.

Details

• Creators:
  Yang, Seongyeong ; Helwig, Todd ; Klingner, Rich ; Engelhardt, Michael ; Fasl, Jeremiah
• Corporate Creators:
  University of Texas at Austin. Center for Transportation Research
• Corporate Contributors:
  Texas. Dept. of Transportation ; United States. Federal Highway Administration
• Subject/TRT Terms:
  • I beams
  • Girders
  • Bridges
  • Live loads
  • Testing
  • Steel I-beams
  • Girders--Testing
  • Bridges--Live loads--Texas--Testing
• Publication/ Report Number:
  FHWA/TX-10/0-5706-1
• Resource Type:
  Tech Report
• Geographical Coverage:
  Texas
• Edition:
  Technical report; Sept. 2006-Aug. 2009.
• Corporate Publisher:
  University of Texas at Austin. Center for Transportation Research
• Abstract:
  Economical constraints on the design of bridges usually necessitate the use of as few girders as possible across the ; bridge width. The girders are typically uniformly spaced transversely with the deck extending past the fascia girders, thereby ; resulting in an overhang. While designers commonly employ rules of thumb with regard to the geometry of the overhang, these ; rules of thumb generally address only the deck in-service strength and deflection requirements, and the effect due to construction ; load is not considered. In particular, the impact of the overhang on fascia girder behavior during construction is not well ; understood. Overhang construction often leads to a torsional load on the girder system that can lead to problems in steel and ; concrete girder bridges during construction. The main issue with concrete girder bridges is excessive lateral rotation in the fascia ; girder, which can cause potential problems of construction safety and maintenance. Field problems on concrete bridges have been ; reported in the state of Texas where the fascia girders experienced excessive rotation during construction. For steel girder bridges, ; the unbalanced overhang loading can lead to both local and global instability. Locally, the overhang brackets often exert a large ; force on the web plate that can distort the web and increase the magnitude of the plate imperfection. Global stability problems ; have occurred primarily on bridge widening projects where a few girders are added to an existing bridge system. The girders in ; the widening are usually isolated from the existing bridge and the unbalanced load from the overhang can cause excessive twist ; that intensifies the global stability of the girder system. ; The objective of this study was to improve the understanding of the bridge behavior due to the unbalanced loading from ; the overhangs and to identify critical factors affecting the girder behavior. The study was also aimed at developing simple design ; methodologies and design recommendations for overhang construction. The research included field monitoring, laboratory tests, ; and parametric finite element analyses. The data from the field monitoring and laboratory tests were used to validate finite ; element models for both concrete and steel girder bridges. Based on the validated models, detailed parametric studies were ; conducted to investigate the effects of the unbalanced loading. Results from the parametric studies were used to identify the ; geometries of girder systems that are prone to problems with the overhangs as well as to provide design suggestions. In addition, ; a closed-form solution for lateral rotation in the fascia girder in a concrete girder bridge was derived using a rigid-body model, ; and was used to develop design methodology and design recommendations for overhang construction.
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• Format:
  PDF
• Funding:
  0-5706-1
• Download URL:
  https://rosap.ntl.bts.gov/view/dot/18278/dot_18278_DS1.pdf
• File Type:
  [PDF - 4.61 MB]
• Collection(s):
  US Transportation Collection
• Main Document Checksum:
  urn:sha256:d35e2489a6e09851d712bdd8227c3138787a422fcd7e715651a8b8cca815dc43