EVALUATION AND FIELD TESTING OF THE DAN RYAN RAPID TRANSIT STRUCTURE

The Dan Ryan rapid transit structure is a 40-span, 4,000-ft-long elevated structure that carries Chicago Transit Authority (CTA) rapid transit trains into and out of the Chicago Loop. The structure, which was completed in 1969, consists of welded stringers and is supported by steel box-girder bents. Splices in the stringers are field bolted. The steel stringers carry two sets of track on a ballasted concrete deck. In January 1978 major brittle fractures ocurred in three of the steel box-girder bents. Since discovering the bent fractures, CTA inspectors found two long cracks in the bottom of the stringers. These cracks were found to originate at welded lateral gusset-plate connections. Approximately 1,800 lateral gussets are used in the 40-span system to attach lateral bracing. Each gusset plate contains a cutout to accommodate the vertical stiffener of the stringer. This detail creates a short gap between the cutout of the gusset and the vertical stiffener. An extensive investigative study of seven spans of the superstructure was carried out to assess the fatigue sensitivity of the stringers with the lateral gusset-plate connections. The study included a review of details used in the structure, field instrumentation and testing, an analytical review, in-depth examination of gusset-plate connections, examination and testing of samples that contain cracks, and the development of retrofits. The information collected during the study, particularly the field testing data, is reviewed. Reviews are also made of the fractographic examination conducted on a sample that contains a 4-in. crack and the in-depth inspection findings. As part of this study retrofits were developed to either shield the crack origin from stress or to increase the gap between the gusset-plate cutout and the vertical stiffener. (Author)

• Record URL:
  http://onlinepubs.trb.org/Onlinepubs/trr/1984/950/950v2-013.pdf
• Record URL:
  https://scholar.google.com/scholar_lookup?title=EVALUATION+AND+FIELD+TESTING+OF+THE+DAN+RYAN+RAPID+TRANSIT+STRUCTURE&author=A.+Osborn&author=M.+Koob&publication_year=1984
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• Supplemental Notes:
  • This paper appeared in Transportation Research Record Number 950, Volume 2, Second Bridge Engineering Conference, conducted by the Transportation Research Board and the Federal Highway Administration, September 24-26, 1984. Publication of this paper sponsored by Committee on Dynamics and Field Testing of Bridges. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved
• Authors:
  • Osborn, Andrew E N
  • Koob, Michael J
• Conference:
  • Bridge Engineering Conference, 2nd, 1984, Washington, DC, USA
• Publication Date: 1984

Media Info

• Media Type: Print
• Features: Figures; Photos; References; Tables;
• Pagination: pp 121-131
• Monograph Title: Second bridge engineering conference. volumes 1 and 2
• Serial:
  • Transportation Research Record
  • Issue Number: 950
  • Publisher: Transportation Research Board
  • ISSN: 0361-1981

Subject/Index Terms

• TRT Terms: Alignment; Beams; Box girders; Field tests; Fracture mechanics; Gusset plates; Railroad bridges; Rapid transit; Spacing; Stiffness; Stringers; Weldments
• Uncontrolled Terms: Vertical alignment
• Geographic Terms: Chicago (Illinois)
• Old TRIS Terms: Welded beams
• Subject Areas: Bridges and other structures; Design; Highways; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00390821
• Record Type: Publication
• ISBN: 03090036593
• Files: TRIS, TRB
• Created Date: Dec 30 1984 12:00AM