Environmental Influences on the Dynamic Characteristics of Supertall Buildings: A Case Study of the Temperature Effect and Metro-Induced Vibrations

The dynamic characteristics of supertall buildings are critical to evaluate structural safety and long-term performance through structural health monitoring. Environmental factors, such as temperature fluctuation, wind, ground motion, and other surrounding excitation, can significantly influence dynamic behavior even in the absence of structural damage, especially for high-density buildings in the area of complex ground space in a megacity. This study investigates the complex interrelationship among temperature, ground motion, and the modal properties (i.e., natural frequency, damping ratio, and mode shape) of the Shenzhen Electronics Group (SEG) Plaza, the world’s first concrete-filled steel tube supertall building exceeding 300 m in height. The structure was subjected to intricate ambient excitation, including vibrations induced by two adjacent metro lines and ongoing construction activities. These factors collectively resulted in abnormal structural vibrations, raising concerns and discomfort among the occupants. Following the initial occurrence of noticeable vibrations, a comprehensive field monitoring campaign was promptly initiated to record vibration data, temperature variations, and ground motion characteristics. The field monitoring program comprised three distinct testing scenarios: (1) a multi-setup, short-duration (15-min) test across 23 floors to estimate the dynamic characteristics of the SEG Plaza; (2) continuous 24-h vibration monitoring of eight representative floors to evaluate the impact of temperature on structural vibration; and (3) ground vibration measurements across three setups to characterize metro-induced excitation. Data from the first scenario were analyzed using a Bayesian operational modal analysis approach incorporating an efficient expectation-maximization algorithm, through which 21 structural modes were identified. Records from the second scenario were used to track the frequencies of four modes over a 24-h period to evaluate their correlation with temperature fluctuations. The third scenario focused on metro-induced ground vibrations, with data analyzed in both the time and frequency domains. A key finding was the identification of a pronounced 2-Hz peak in the power spectral density of the metro-induced vibrations, which coincides with the building’s 12th mode. This resonance phenomenon raises concerns regarding potential long-term fatigue effects. Additionally, modal parameters were tracked over a 12-h period in the third scenario, demonstrating the influence of temperature and ground motion on the building’s dynamic behavior. The results provide valuable insights for future research on environment–structure interactions in supertall buildings and offer practical recommendations for vibration testing in urban environments with multisource excitation.