Investigation of Rooftop Mast–Induced Abnormal Vibrations of a 76-Story Building and Effectiveness of Mitigation Measures via Noncontact Measurements

Abstract

On May 18, 2021, 76-story SEG Plaza in Shenzhen, China experienced sudden abnormal vibrations, leading to building resident evacuation and prompting considerable public concern. Given accessibility constraints and safety hazards, noncontact field measurements from SEG Plaza after the sudden vibration event were conducted using an interferometric radar system to explore the reason for the abnormal vibrations and assess its structural condition. Subsequent studies revealed that the abnormal vibrations originated from vortex-induced vibrations of the rooftop mast under specific wind conditions. Thus, the mast was removed as a mitigation measure. Its removal was followed by repeated noncontact measurements to evaluate the effectiveness of the mast removal measures. In displacement measurements of high-rise structures, weaker and higher structural vibration modes are prone to being overwhelmed by noise and dominant modes, resulting in inaccurate identification or loss of modal information. Therefore, a hybrid output-only modal identification scheme combining modal extraction, block bootstrap, and deterministic operational modal analysis techniques was adopted in this study to achieve weak modal enhancement and uncertainty quantification. Firstly, the accuracy and effectiveness of the hybrid scheme were validated by numerical simulations. The hybrid scheme then was applied to analyze the noncontact vibration measurements from SEG Plaza before and after the mast removal to identify its structural dynamic properties, explorie the cause of the abnormal vibrations, and evaluate the effectiveness of the mitigation measure. This study developed an efficient approach for noncontact vibration measurements and high-accuracy modal estimation of high-rise structures to assess the serviceability and structural safety of SEG Plaza.