A COMPARATIVE STUDY OF PASSIVE SEISMIC APPROACHES FOR MULTI-STORY BUILDING FUNDAMENTAL FREQUENCY IDENTIFICATION

Abstract

Resonance due to earthquakes can significantly increase the likelihood of multi-story buildings collapsing; therefore, a reliable identification of the fundamental frequency is critical for estimating the building’s seismic performance. This study investigates the fundamental frequency by means of three different passive seismic approaches, i.e., the horizontal-to-vertical spectral ratio (HVSR), the floor spectral ratio (FSR) and the random decrement method (RDM). Ambient vibrations recorded on multiple floors in 12 multi-story buildings located in Aceh Province, Indonesia, were used in the present study. Initially, signal stability was assessed qualitatively through waveform continuity, spectral repeatability, and visual inspection of inter-channel consistency. Windows affected by impulsive disturbances or unstable spectral characteristics were excluded before further analysis by means of HVSR, FSR, and RDM. The findings suggest that the HVSR approach always suggests the lowest frequency compared to the others. Furthermore, HVSR seems sensitive to vertical motion, instead of the horizontal structural response. HVSR is likely also sensitive to soil-layer resonance and soil–structure interaction. This study finds that FSR and RDM are effective at capturing the inherent fundamental frequencies of buildings. Both FSR and RDM suggest well-matched building frequency estimation. In conclusion, the applied approaches in the present study offer a straightforward conceptual framework for assessing building dynamic parameters in site-specific environments.