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Earthquake and ambient vibration monitoring of the steel-frame UCLA factor building

Earthquake Spectra

By:
, , and
DOI: 10.1193/1.1946707

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Abstract

Dynamic property measurements of the moment-resisting steel-frame University of California, Los Angeles, Factor building are being made to assess how forces are distributed over the building. Fourier amplitude spectra have been calculated from several intervals of ambient vibrations, a 24-hour period of strong winds, and from the 28 March 2003 Encino, California (ML = 2.9), the 3 September 2002 Yorba Linda, California (ML = 4.7), and the 3 November 2002 Central Alaska (Mw = 7.9) earthquakes. Measurements made from the ambient vibration records show that the first-mode frequency of horizontal vibration is between 0.55 and 0.6 Hz. The second horizontal mode has a frequency between 1.6 and 1.9 Hz. In contrast, the first-mode frequencies measured from earthquake data are about 0.05 to 0.1 Hz lower than those corresponding to ambient vibration recordings indicating softening of the soil-structure system as amplitudes become larger. The frequencies revert to pre-earthquake levels within five minutes of the Yorba Linda earthquake. Shaking due to strong winds that occurred during the Encino earthquake dominates the frequency decrease, which correlates in time with the duration of the strong winds. The first shear wave recorded from the Encino and Yorba Linda earthquakes takes about 0.4 sec to travel up the 17-story building. ?? 2005, Earthquake Engineering Research Institute.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Earthquake and ambient vibration monitoring of the steel-frame UCLA factor building
Series title:
Earthquake Spectra
DOI:
10.1193/1.1946707
Volume
21
Issue:
3
Year Published:
2005
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Earthquake Spectra
First page:
715
Last page:
736