LAUSR

Abstract Dynamic properties of structures, in terms of frequencies and mode shapes, represent inherent characteristics and health states of structural systems. A method for extraction of modal parameters of structures based on distributed measurements of dynamic strains is described in this article. AT-BOTDA (Amplitude Transfer-Brillouin Optical Time Domain Analysis) optical fiber sensor based on Brillouin scattering is employed for distributed measurements of dynamic strains in a laboratory beam. SSI-DATA (Data-driven Stochastic Subspace Identification) is selected in the formulation of the method, based on its capability for efficient analysis of large amounts of data. The analysis approach involves pre-processing of the distributed data based on basic principles of dynamics, determination of the sensing range, building the strain state space model, extracting modes and improving the results with selection of the sensing points. Laboratory experiments on a beam indicate that distributed vibration strains collected by AT-BOTDA are sufficient for convergence, resulting in an accurate determination of the first two mode shapes.