• earthquake-damaged building;
  • dynamic property;
  • natural period change;
  • ambient vibration;
  • China


Full-scale in situ ambient vibration tests have been performed in different regions of China since 2008. Reliable data on 35 buildings in the Sichuan province and 18 buildings in Shanghai have been used for identifying the structural dynamic properties. Every building was tested twice, at time intervals of 1 to 2 years. This paper first describes the statistical analysis results of the measured records and then the time–frequency domain analysis on dynamic responses of a specific monitored building subjected to strong motion. Furthermore, the estimated dynamic characteristics of the buildings are presented. The damping ratio shows a period-dependent characteristic, and the natural periods of buildings in Sichuan shifted after 2 years. Subsequent discussion on the natural period change phenomenon reveals that the natural period changes are affected by a number of factors, including story number, construction year, loading history, and observation time intervals. The long-term time effects on concrete, the self-healing ability of cracked concrete, and the change in soil condition are discussed to explain the natural period wandering. Copyright © 2012 John Wiley & Sons, Ltd.