Operational modal analysis of a nine-story concrete core wall building

Abstract

This paper describes the experimental modal identification techniques used to identify the dynamic properties of a nine-story concrete core wall building located on the University of British Columbia campus in Vancouver, Canada. Constructed in 1963, in a region of high seismic risk, the tower is slated for retrofit in the near future. In order to identify the dynamic properties of the structure, an ambient vibration test was performed using three instrument setups, synchronized via GPS, and positioned strategically throughout the building. Frequency domain decomposition and stochastic subspace identification methods were used to determine and validate the dynamic characteristics of the tower. The natural modes of vibration, frequencies, and damping ratios are presented. The results indicate that the structure exhibits rocking in the foundations as well as significant interaction with the adjacent structure.