This study evaluates several methods for the detection and location of a perturbation along a bending beam. Unlike previous studies, the situation chosen is comparable to that encountered in-situ after an earthquake. Indeed, assessment of earthquake damage to buildings is a crucial factor in crisis management. Buildings can be tested appropriately using operational modal analysis methods based on ambient vibration data. In this study, we tested four modal-based methods to locate the perturbation. The mode shapes and eigenfrequencies of a beam were evaluated in the laboratory using the frequency domain decomposition method applied to ambient vibrations simulated along a one-dimensional bending beam, using the finite element method and recorded on a poly(methyl methacrylate) (Plexiglas) beam-like free-clamped structure. The data show that the uniform load surface curvature method is the most efficient, and it allows for accurate estimation of the location of the perturbation, whatever its nature (e.g., multiple, simple, different positions). The experimental data also show that frequency domain decomposition resolution of the mode shapes must be as accurate as possible, otherwise it is impossible to locate transient perturbations over short periods.
