by Patrick Hipley, Moh Huang and Anthony Shakal
Hipley, Patrick, Moh Huang and Anthony Shakal (1998). Bridge Instrumentation and Post-Earthquake Evaluation of Bridges. SMIP98
Seminar on Utilization of Strong-Motion Data, p. 53 - 62.
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As the number of large civil structures instrumented for strong motion is increasing, efforts towards utilizing the
earthquake data collected from these structures is also increasing. The studies are geared towards verifying seismic
engineering design assumptions by comparing the theoretical models to the actual readings. Efforts to utilize the data
ranging from simple comparison of the estimated structural period of vibration with the recorded free vibration, to
complex comparisons of non-linear time-history models are underway. Many more studies are needed to take full advantage
of this valuable data.
Accurately monitoring bridge movements during a large earthquake is necessary to advance our
understanding of how these massive structures are affected by seismic input. Bridges of different structure types react
differently to the same seismic wave patterns. Dynamic soil-structure interaction can be studied and theories can be
verified or disproved based on the actual readings. Before strong motion sensors were placed at ground sites or on
civil structures, theories were based on very little data. Therefore, the data collected from large earthquakes with
these sensors are invaluable to the seismic engineering community.
The California Department of Transportation (Caltrans) and the California Strong Motion Instrumentation Program (CSMIP) of the California Department of
Conservation's Division of Mines and Geology have instrumented more than 50 Caltrans bridges throughout the State since
the 1989 Loma Prieta earthquake. In addition, CSMIP and Caltrans are installing more near-real-time
stations at selected bridge sites in the State. Consequently, more near-real-time strong-motion data will be available
quickly after an earthquake. These data provide information on ground shaking and response of the bridge structure, and
are useful not only for improving seismic design practices but for post-earthquake damage evaluation of bridges. This
paper describes the current status and future plan of the Caltrans/CSMIP bridge instrumentation project, and discusses
quick application of strong-motion data to post-earthquake evaluations of bridges. Cases of quick application of near-
real-time data are presented and criteria for determining post-earthquake inspection of bridges are discussed.