Full-scale measurements of mode coupling vibrations during super typhoons on a rectangular supertall building with limited sensors

Abstract

Towards a complete and accurate assessment of the model parameters (i.e., frequency, damping ratio, and mode shape) of supertall buildings, this study proposes a new modal identification method named SCA-MBSDA based on the framework of sparse component analysis (SCA) and modified Bayesian spectral density approach (MBSDA). The feasibility and uncertainty of the SCA-MBSDA method are analyzed in an underdetermined case using a three-degree-of-freedom frame structure via numerical simulations. Through measurements from a wireless biaxial ultra-low frequency accelerometer atop the building, the variations in the first three modal parameters of a 125 m high rectangular supertall building with significant multi-mode coupling vibrations (maximum accelerations >15 cm/s2) are illustrated during typhoons Hato and Mangkhut. The results demonstrate the high effectiveness of the SCA-MBSDA method in identifying time-varying structural frequencies and mode shapes. During super typhoon conditions, the third mode of the monitored building exhibits a significant decrease in natural frequency and modal stiffness, with reduced rates of 9 % and 17 %, respectively. The averages of the first three mode directions obtained from the measurements agree well with the values obtained from the finite element model (FEM). This paper aims to provide a feasible identification method to enhance the understanding of the changes in the first three modal properties of supertall buildings during typhoons.