Ambient vibration testing & modal identification of an office building

Ambient vibration test and modal identification of a 15-story office building newly completed in Tokyo are described in this paper. There are 200 DOF ’s in the test model of the building with 48 real acceleration measurements and 152 virtual measurements under the rigid floor assumption. It took less one-day to finish all the ambient response measurements in four setups, 14-channel for one setup with two sensors as references. The Frequency Domain Decomposition (FDD) technique is adopted for ambient or output-only, modal identification. Within interested frequency range of 0 to 4.5 Hz, altogether 9 modes were accurately identified. As one of the major focus of the project, accurate damping estimation was conducted based on damping convergence with increasing frequency resolution of the PSD measurement. The identified modal frequencies and mode shapes were utilized for FE model correlation and tuning. Excellent agreement of modal parameters up to 9 modes has been achieved with respect to the final tuned FE model.