Recorded Earthquake Response of the new Self Anchored Suspension (SAS) Bridge of the San Francisco Bay Bridge System

Mehmet Celebi

Submitted September 11, 2022, SCEC Contribution #11984, 2022 SCEC Annual Meeting Poster #270

I analyze the seismic performance of the Self Anchored Suspension (SAS) Bridge of the San Francisco Bay Bridge System by evaluating response data recording during the October 14, 2019 Mw4.6 Pleasant Hill earthquake (www.stronmotioncenter.org) and by the seismic monitoring system installed on the bridge. The new SAS bridge went into service within the last decade as a replacement for the older truss bridge that spanned between Yerba Buena Island and Oakland. During the October 19, 1989 M6.9 Loma Prieta earthquake, which occurred ~100 km south of the Bay Bridge, a section of the upper deck of the truss bridge fell onto the lower deck – thus closing this important lifeline between San Francisco and Oakland. The replacement SAS is unique and, as the name indicates, is self-anchored and suspended by a single tower that is pivotal in trafficking the cable and hanger system to support the eastbound (E) and westbound (W) decks. At each of the west and east ends of the SAS, there is a hinge system that ties the W and E decks to the skyways. The SAS bridge is extensively instrumented by the California Geological Survey’s Strong Motion Instrumentation Program, in collaboration with the California Department of Transportation. There are approximately 85 channels of accelerometers in the seismic monitoring system that recorded low-amplitude responses of the bridge system; however, only one set of response data is studied herein.
The data indicate a complex and identifiable coupled response of the deck, tower, and cable system. Both acceleration and displacement time-history data are used to extract significant frequencies using system identification methods, including spectral analyses.

Key Words
instrumentation, response, bridge,

Citation
Celebi, M. (2022, 09). Recorded Earthquake Response of the new Self Anchored Suspension (SAS) Bridge of the San Francisco Bay Bridge System. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Engineering Implementation Interface (EEII)