The new self-anchored suspended San Francisco Bay Bridge segment and its Response and Behavior during a small earthquake, and highlights of seismic monitoring of structures
Mehmet Celebi
USGS
- Date & Time
- Location
- Hybrid - in person (Moffett) and online via MS Teams
- Summary
Instrumented by the California Strong Motion Instrumentation Program (CSMIP) and in absence of strong shaking data, the new Self- Anchored Suspension (SAS) Bridge of the San Francisco Bay Bridge System is studied using response data recorded during the October 14, 2019, Mw4.6 Pleasant Hill earthquake. The new bridge went into service within the last decade as a replacement for the older truss bridge that spanned between Yerba Buena Island and East Bay. During the October 19, 1989, M6.9 Loma Prieta earthquake, a section of the upper deck of the old truss bridge fell onto the lower deck. The unique SAS Bridge is suspended by a single tower that is pivotal in trafficking the cable and hanger system. The response data analyses highlight the complex and yet identifiable coupled response of the deck, tower, and cable system. Using system identification methods including spectral analyses of both acceleration and displacement time history data, the fundamental frequencies (periods) and critical damping percentages are extracted for the main components (tower, deck, and cables) of the bridge where the sensors are deployed. There is strong evidence of a beating effect attributed to low critical damping percentages and coupled modes.