On Damping Experimental Estimation

Experimental estimation of damping is currently not a comprehensively solved problem. Although modal frequencies and mode shapes can be confidently and quite easily measured by means of dynamic tests on civil structures, an accurate identification of damping ratios needs further development. Experimental values can be characterized by large error bounds mainly because damping is strongly influenced by the magnitude of the dynamic response of a structure. In this paper the main issues concerning identification of modal damping ratios are discussed in order to define methods for a reliable estimation, reduce uncertainties and characterize error bounds. According to this aim, a literature review has been carried out to find best practice criteria for modal parameter identification, in particular damping. A procedure for optimized modal parameter estimation via Stochastic Subspace Identification is also proposed. These efforts aim at standardization of testing and data processing techniques. The final objective is a decrease of the level of uncertainty associated to the estimated modal parameters and, above all, damping ratios. Reduction of scatter and standardization of data processing procedures finally give the opportunity to build a reliable database for calibration of empirical formulations to be used, in the framework of structural and seismic design, for modal damping prediction.