Dynamic characteristics of a tall building during typhoons

Abstract eng:
This paper presents work on modal identification of a tall building using ambient vibration data collected during two recent typhoons, namely Nuri (22-23 August 2008) and Hagupit (21-22 September 2008). The paper discusses the procedure and difficulty encountered during instrumentation and data analysis phase. Cross-correlation functions among measured degrees-of-freedom are estimated from the ambient vibration data, which can be used for modal identification as if there were free-vibration data, assuming uncorrelated random excitations. A method based on least-square fitting of the correlation functions is adopted for modal identification. It is found that the building has closely-spaced translational modes in its principal directions, which agree with their finite element model estimates established at the design stage. As a result of the closely-spaced modes, the principal directions of the identified modeshapes vary across different time segments. The modal properties of the building are tracked during the typhoon events, spanning periods from normal to high winds. Investigation of identified frequencies versus the corresponding modal vibration level indicates a significant inverse trend.

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