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Duration of Earthquakes, Comparison between Ground Motion and Structural Motion.
O'Rourke, M. J.; Serna, R.; Johnson, R. U.
National Science Foundation, Washington, DC., May 1982, 72 p.
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Several ground motion durations relevant to the behavior of structures during earthquakes are compared. Time periods are determined for which the relative displacements in structures subjected to earthquake ground motion are largest. The ground motion durations are compared with the time interval during which there is significant seismically induced structural motion. Results are presented of studies of buildings affected by earthquakes in Sendai, Japan and in San Fernando, California. Degradations in the effective stiffness of the buildings occurred during both earthquakes. The time period during which this structure stiffness degradation occurred is determined for a number of structures affected by the 1971 San Fernando earthquake. This time period is then compared to the period of strong structural response. It is shown that stiffness degradation generally begins before the start of strong structural response and ends after maximum displacement has occurred.
Dynamic response; Ground motion; Damping; Earthquake engineering; Earthquake resistant structures; San Fernando (California); Soil structure interactions; Earth movements; California; Resonant frequency; Sendi (Japan); Japan; Seismic waves