PRELIMINARY INVESTIGATION OF THE SEISMIC VULNERABILITY OF THE ALASKAN WAY VIADUCT. FINAL TECHNICAL REPORT

The University of Washington (UW) team reviewed the Washington State Department of Transportation (WSDOT) report entitled "Earthquake Analyses of the Alaskan Way Viaduct" and performed an independent assessment of two typical sections of the structure. Additional analyses were performed to investigate the influence of some factors that were not considered in the WSDOT report. The input motion and geotechnical characteristics assumed in the WSDOT report were consistent with the information available to the WSDOT and to the UW. However, the paucity of information available regarding the seismological risk and the subsoil conditions precluded the possibility of reliably estimating the input motion, foundation stiffnesses, foundation capacities, and potential for liquefaction. Inspection of the structural plans suggested that timber-concrete spliced piles in the section of the structure built by the WSDOT might be particularly vulnerable. The elastic dynamic models generated by WSDOT and those constructed for this study were found to give comparable natural periods in the first three modes. Those in the higher modes differed because of the disparate ways in which the structures were modelled. However, the higher modes provided only a small portion of the total response, so the differences in calculated response were small. For the WSDOT designed part of the structure, g-ratings and dynamic code ratios were established by assuming that the reinforcement would reach its yield strength. The present study found the structure to be generally weaker than did the WSDOT study. Some of the ratings showed a consistent relationship with those given by the WSDOT study, while others showed considerable scatter. Regardless of the resolution of the discrepancies, both analyses indicated that the demands on structural members would be likely to greatly exceed their capacities. The main shortcomings in the structure appeared to be inadequate confinement steel and development lengths that were too short. Because no distress was observed after the 1965 Seattle earthquake, these calculations are undoubtedly conservative. However, the response of these brittle details cannot be predicted reliably without further investigation. The University of Washington team is proposing further study to verify the seismic safety of the structure.

• Record URL:
  • http://www.wsdot.wa.gov/research/reports/fullreports/265.1.pdf
• 
• Corporate Authors:

  University of Washington, Seattle

  Seattle, WA  United States  98195

  Washington State Department of Transportation

  Transportation Building, 310 Maple Park Avenue SE, P.O. Box 47300
  Olympia, WA  United States  98504-7300

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Brown, C B
  • Eberhard, M O
  • Kramer, S L
  • Roeder, C W
  • Stanton, J F
• Publication Date: 1992-4

Language

• English

Media Info

• Features: Figures; Tables;
• Pagination: 90 p.

Subject/Index Terms

• TRT Terms: Bridge foundations; Earthquake resistant design; Elastic analysis; Geotechnical engineering; Safety; Viaducts
• Old TRIS Terms: Elastic analysis (Structural)
• Subject Areas: Bridges and other structures; Design; Geotechnology; Highways; Safety and Human Factors; I24: Design of Bridges and Retaining Walls;

Filing Info

• Accession Number: 00625000
• Record Type: Publication
• Report/Paper Numbers: WA-RD 265.1
• Contract Numbers: GC8719, Task 43
• Files: TRIS, USDOT, STATEDOT
• Created Date: Sep 28 1993 12:00AM