Six-component seismic monitoring of a high-rise building

Abstract

We report seismic observations and studies on a high-rise building deployed with six-degree-of-freedom (6-DOF) seismometers. By analyzing the horizontal-to-vertical spectral ratios (HVSRs) of translational components, five resonant modes within 2 Hz are identified. By analyzing the improved rotational vertical-to-horizontal spectral ratios (RVHSRs) of rotational components, three torsional resonant modes are identified; two torsional resonant modes are consistent with those of the translational records, while the higher frequency mode is not observed in the translational motions. Continuous 6C seismic observations over 70 days indicate that the various resonant frequencies of high-rise buildings are related to multiple factors, such as human activity and rainfall levels. The most interesting phenomenon is that three translational resonant modes exhibit diurnal variations; two torsional resonant modes do not have the same trend as translational resonances, which indicates that the translational and torsional resonant modes of the building possibly have different physical mechanisms. In addition, analyses of ambient noises with the directional HVSR method and analyses of vibration caused by earthquakes commonly show that building vibration is directional; furthermore, there are nonpositive correlations of displacements between the middle and top floors of the high-rise building under multiple earthquake events. The nonlinear response of the high-rise building concerning the height is consistent with the responses reported in former studies.