Northridge Earthquake Influence on Bridge Design Code


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Title: Northridge Earthquake Influence on Bridge Design Code

Author(s): R. Zelinski

Publication: Special Publication

Volume: 187


Appears on pages(s): 17-28

Keywords: analysis; bridges; concretes; design; ductility; prestressed; reinforced; retrofit; seismic

Date: 6/1/1999

The Northridge Earthquake, January 17, 1994, caused partial collapse of seven freeway bridges, and damage to 230 others. Vertical accelerations, failed hinge restrainers, and column flare behavior were cited as causes of collapse and major damage. It is true that these factors, plus a few others, contributed to the collapse and damage can be summarized as insufficient ductility in the bridge structural frames. Furthermore, the bridge elements which failed in a non-ductile fashion behaved predictably. The details which led to the failures are no longer used in new bridge designs. These brittle details are converted to ductile ones in retrofit designs. This paper will investigate the undesirable bridge behavior observed in the Northridge Earthquake, and discuss how most of these issues are already covered in new bridge design codes. Finally, procedures adopted or proposed to correct the remaining issues and improve bridge behavior in a more reliable manner, as compared to undesirable Northridge Earthquake bridge response, will be outlined.