Skewed Steel Bridges, Part II: Cross-Frame and Connection Design to Ensure Brace Effectiveness

Skewed bridges in Kansas are often designed such that the cross-frames are carried parallel to the skew angle up to 40°, while many other states place cross-frames perpendicular to the girder for skew angles greater than 20°. Skewed-parallel cross-frames are longer and may require different connections than cross-frames oriented perpendicular to the girder. Therefore, it is important to determine whether the cross-frames and their corresponding connecting elements placed in a parallel-to-skew configuration are sufficiently designed to resist lateral torsional buckling demands using current Kansas Department of Transportation (KDOT) practices. The authors have performed a study to investigate the effect of cross-frame orientation, skew angle, and cross-frame connection upon bridge system behavior and cross-frame stresses. In a suite of detailed 3D, solid finite element analyses models of skewed bridge systems, cross-frame layout, connection thickness and type, and skew angle were varied. Skewed bridge systems with cross-frames placed parallel to the skew angle as well as systems with cross-frames arranged in a staggered configuration were considered. Varying bent plate connection thicknesses and a half-pipe connection were also analyzed. Cross-frame spacing of 4.6 m (15 ft) and 9.14 m (30 ft) were examined; severe cross-frame spacing of 13.7 m (45 ft) was also considered to examine behavior at very long unbraced lengths. The findings of this study showed that skew angle, skew configuration, and connection type all influenced the strength and stiffness of system. The data showed that cross-frame placed parallel to skew up to an angle of 40° performed similar to or better than cross-frames oriented perpendicular to skew for every given skew angle and connection type.

• Record URL:
  http://dmsweb.ksdot.org/AppNetProd/docpop/docpop.aspx?clienttype=html&docid=9935097
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• Summary URL:
  http://dmsweb.ksdot.org/AppNetProd/docpop/docpop.aspx?clienttype=html&docid=9935099
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/32612
• Corporate Authors:

  University of Kansas, Lawrence

  Department of Civil, Environmental and Architectural Engineering
  1530 West 15th Street
  Lawrence, KS  United States  66045-7609

  Kansas Department of Transportation

  Bureau of Research
  2300 SW Van Buren Street
  Topeka, KS  United States  66611-1195
• Authors:
  • Zhou, James
  • Bennett, Caroline
  • Matamoros, Adolfo
  • Li, Jian
• Publication Date: 2017-8

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; References; Tables;
• Pagination: 193p

Subject/Index Terms

• TRT Terms: Bridge design; Finite element method; Mathematical models; Skew bridges; Structural connection
• Uncontrolled Terms: Cross frame spacing; Cross frames; Orientation (Direction facing); Skew angles
• Geographic Terms: Kansas
• Subject Areas: Bridges and other structures; Design; Highways;

Filing Info

• Accession Number: 01643867
• Record Type: Publication
• Report/Paper Numbers: K-TRAN: KU-13-7
• Contract Numbers: C1939
• Files: NTL, TRIS, ATRI, STATEDOT
• Created Date: Aug 21 2017 11:15AM