Continuous data streams from translational and rotational seismometers installed in TAIPEI 101 enable monitoring of the natural frequencies on different time scales. Using the 2014 seismic data recorded on the 90th floor of this high-rise building and the meteoro-logical data from a weather station located just 1 km away, we explored the characteristics and controlling factors of the ambient vibrations in TAIPEI 101. Using the random decrement technique, the three modal frequencies in translation were identified as 0.15 Hz (F1), 0.43 Hz (F2), and 0.78 Hz (F3). For rotation around the vertical axis, the modal frequencies were 0.23 Hz (R1), 0.59 Hz (R2), and 0.93 Hz (R3). In translation, TAIPEI 101 exhibits a trend of increasing modal frequency with increasing temperature but decreasing modal frequency with increasing wind velocity. The trend with temperature is reversed in rotation motion. The different frequency versus temperature relationship seen for rotational and translational motion demonstrates the importance of introducing rotational motion analysis into structural health monitoring. The change in modal frequencies were also found to decrease with growing amplitude. It is intriguing that F1 exhibits a weaker dependency with amplitude with respect to the higher modes, which may be associated with the sup-pression of F1 vibration caused by the damper installed in TAIPEI 101. Other than long-term (seasonable) variation, we also highlight the hourly variation of the first-mode amplitude throughout a day by comparing with weather and mobility data. Other than the atmospheric conditions that strongly influence the modal frequencies in long-term behavior, we found that human activities may play an important role in the short-term vibration characteristics of the building.
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