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Record Processing for Analysis of Dams

Get compatible, unprocessed records for in-depth analysis of dams in the relevant frequency range. Ensure zero displacement and understand the interaction between dams and free-field sites. Recover multiple modes for accurate assessment.

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Record Processing for Analysis of Dams

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  1. Record Processing for Analysis of Dams Daniel R.H. O’Connell Seismotectonics and Geophysics Group Bureau of Reclamation Denver, CO 80225

  2. Records Must be Compatible. • Many engineering codes internally integrate input accelerations, to velocity or displacement.

  3. Need Zero Displacement at the End of the Record . • Why? Sometimes there are rigid boundaries in some part of the numerical model Nonzero static displacements will introduce spurious internal strains in the model because they are incompatible with artificial boundary conditions. It is not uncommon for this to be overlooked in engineering analyses.

  4. Need Unprocessed Records. • To allow more detailed independent analysis of the records.

  5. Relevant Frequency Range for dams. • Generally > 0.25 Hz (4 s) and < 15 Hz (often < 10 Hz). • Dams generally resonate at frequencies > 1 Hz.

  6. Dams often interact with nearby “free-field” sites. • Particularly arch dams. Paicoma Dam is a notable example, where the peak accelerations on the left abutment probably reflect strong arch stresses transferred to the abutment near the fundamental mode of the dam (~3 Hz). • I was able to recover the first 6 modes of an arch dam at 200 m downstream of the dam via spectral analysis of ambient vibrations. The fundamental model of the dam was visible in the time domain in the ground velocity coda of local earthquakes recorded on the abutment of the dam.

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