Application of ambient vibration experimental analysis on large structures

The ambient vibration measurement is a kind of output data-only dynamic testing that employs natural environmental stimulation sources like traffic and wind. Since input data cannot be used, an output-only modal analysis approach must be used for testing in an ambient vibration environment. When doing modal analysis using output-only data, it is necessary to use a specialized modal identification approach that can handle extremely tiny magnitudes polluted by noise. There are two modal analysis techniques used, and they are complimentary. In the frequency domain, we have the relatively straightforward peak picking (PP) approach, while in the time domain, we have the more complex stochastic subspace identification (SSI) method. This article discusses the use of experimental modal analysis and ambient vibration testing on major civil engineering constructions. These two examples are a 15-story reinforced concrete shear core building and a concrete-filled steel tubular arch bridge. The findings demonstrate that both methods are capable of accurately pinpointing the frequencies. In most circumstances, the stochastic subspace identification methodology provides more realistic mode shapes and can discover frequencies that would otherwise be overlooked by the peak selecting method.