Effect of Implementing Lean-on Bracing in Skewed Steel I-Girder Bridges

Skew of the supports in steel I-girder bridges cause undesirable torsional effects, increase cross-frame forces, and generally increase the difficulty of designing and constructing a bridge. The girders experience differential deflections due to the skewed supports, and undesirable effects arise when the girders are linked transversely. Before the placement of the deck, the main method of linking the girders transversely is through the use of cross-frames. The cross-frames are designed to provide stability during construction and distribute transverse loads through the bridge girders; this is their primary role. Cross-frames also help control differential displacement during deck placement and distribute vertical loads in the bridge’s elastic and inelastic ranges. The cross-frames are not specifically designed for these tasks; these are the secondary roles of the cross-frames. Lean-On bracing has been proposed to reduce skew effects caused by traditional cross-frames. While having been shown to improve skew effects, the alternative cross-frame designs have not been evaluated on the effect they have on the cross-frames’ secondary roles. This paper describes a study of the effects Lean-On bracing has on the secondary roles of cross-frames. Three-dimensional Finite Element Models were used to perform a study involving changes in skew angle and cross-frame design. The rotation of the girders, maximum cross-frame stresses, load distribution, and differential displacement between the girders were used to characterize the behavior of the bridges. For the bridge type studied, the only major difference in performance was that the maximum cross-frame stresses were reduced for the bridges modeled with Lean-On bracing.

• Record URL:
  http://www.utrc2.org/sites/default/files/Final-Report-Effect-of-Implementing-Lean-On-Bracing.pdf
• 
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/31704
• Supplemental Notes:
  • This document was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
• Corporate Authors:

  College of New Jersey

  Department of Civil Engineering
  Ewing, NJ  United States 

  University Transportation Research Center

  City College of New York
  Marshak Hall, Suite 910, 160 Convent Avenue
  New York, NY  United States  10031

  Office of the Assistant Secretary for Research and Technology

  University Transportation Centers Program
  Department of Transportation
  Washington, DC  United States  20590

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Bechtel, Andrew
• Publication Date: 2016-9-30

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Figures; Photos; References; Tables;
• Pagination: 23p

Subject/Index Terms

• TRT Terms: Bracing; Bridge design; Bridge members; Deflection; Finite element method; Frames; Girder bridges; Girders; Skew bridges; Steel bridges
• Subject Areas: Bridges and other structures; Design; Highways;

Filing Info

• Accession Number: 01624429
• Record Type: Publication
• Contract Numbers: 49198-21-27
• Files: UTC, NTL, TRIS, ATRI, USDOT
• Created Date: Jan 30 2017 10:44AM