Tacoma Narrows bridge, built in 1950 to replace an earlier structure, has a main span of 2800 ft (854m) and a total length of 5000 ft (1524m). The bridge is located in an area that is known to be subjected to infrequent great earthquakes. Recognising the potential vulnerability of the bridge, the agency responsible commissioned a study to evaluate its seismic vulnerability. When the bridge was designed in the late 1940's, great care and detail were paid to its static design, as well as to wind loading and the dynamic influence of wind. Seismic design of the bridge, on the other hand, is not in keeping with present day practice. The bridge towers are founded on caissons with maximum embedment of about 75 ft (23m,) in 1000 ft (300m) deep glacial till. The viaducts were built from the damaged remains of the previous Narrows bridge. Seismic analysis was based on a static coefficient of 3.1% for the towers and 6.2% for the remainder of the bridge. The scope of the studies included development of seismic performance criteria, geotechnical and seismic risk studies, synthesis of multi-support incoherent ground motion input, field measurement of vibration properties, and vulnerability assessment. (A) For the covering abstract see IRRD 882313.


  • English

Media Info

  • Pagination: p. 539-46

Subject/Index Terms

Filing Info

  • Accession Number: 00729494
  • Record Type: Publication
  • Source Agency: Transport Research Laboratory
  • ISBN: 0-419-21210-8
  • Files: ITRD
  • Created Date: Dec 26 1996 12:00AM