Structural Response Analysis of a Reinforced Concrete Building with the Excitation of Microtremors and Passing Subway Trains

Abstract eng:
A period of more than 2 days measurements of the ambient seismic noise were conducted inside a reinforced concrete (RC) building in central Beijing. The temporal seismic array consists of 16 3-component short-period seismometers, with 2 on each floor, from the basements to the 7th floor in this 7-story RC building. Two types of analysis were conducted to the measured data to extract the structural response of the building: 1) the horizontal to vertical (H/V) spectral ratio method to the continuous ambient noise; and 2) the seismic interferometry analysis with a deconvolution procedure to the seismic sources generated by the passing subway trains. Both analyses indicate the fundamental resonance frequency of this RC building is about 2.2 Hz in EW and 2.9 Hz in NS, with an unknown mode at the frequency of 5 Hz. The H/V analysis indicates that the major noise source comes to the building from EW direction, consisting with the urban traffic layout in central Beijing area. The seismic interferometry analysis of the structural response to the passing subway trains gives an estimate of the damping ratio of this RC building is about 0.17, a very efficient level of damping to resonant vibrations. We conclude that structural analysis using the ambient seismic noise (microtremors) as excitation input may provide an economical and flexible way to supplement the traditional strong ground motion analysis using only accelerograms in building vulnerability assessment to seismic hazard. This project is supported by Ministry of Science and Technology of China with Project No. 2006DFA21650 and the Institute of Earthquake Science (Project No. 0207690229).

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