Blind Identification of Civil Structures

This paper presents a new Blind Source Separation (BSS) method for the modal identification of structural systems. Independent Component Analysis (ICA), a popular tool to perform BSS, suffers performance issues at the levels of damping commonly encountered in structural applications. In this context, methods based on Second Order Blind Identification (SOBI) have shown significant improvement over ICA. However, traditional SOBI methods suffer due to the presence of non-stationary sources such as those that occur during earthquakes and other transient excitations. In this paper, a new technique, called the Modified Cross-Correlation (MCC) method, is developed to address the problem of output-only modal identification of civil structures. The conditions in which the problem of structural system identification can be posed as a BSS problem are discussed. The simulation and experimental results in terms of identified natural frequencies, mode shapes, and damping ratios are presented to show that the MCC method achieves better performance over traditional ICA and SOBI methods.