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Shock and Vibration
Volume 17 (2010), Issue 4-5, Pages 383-395

Some Remarks on Experimental Estimation of Damping for Seismic Design of Civil Constructions

Carlo Rainieri,1 Giovanni Fabbrocino,1 and Edoardo Cosenza2

1Structural and Geotechnical Dynamics Lab StreGa, Department SAVA, University of Molise, School of Engineering, Via Duca degli Abruzzi, 86039 Termoli, Italy
2Department of Structural Engineering, University of Naples “Federico II”, Via Claudio 21, 80125 Naples, Italy

Received 17 June 2010; Accepted 17 June 2010

Copyright © 2010 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Experimental estimation of damping is currently not a comprehensively solved problem. Although modal frequencies and mode shapes can be measured confidently and quite easily 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 their reliable estimation, to reduce uncertainties and characterize error bounds. According to this aim, a procedure for optimized modal parameter estimation via Stochastic Subspace Identification is also proposed. Then data collected from an extensive literature review are analyzed depending on the type of structure in order to point out the main factors affecting damping. Moreover, a comparison with provisions about structural damping given in National and International seismic codes for structural design of civil structures is reported. This process demonstrates that the development of a damping database based on homogeneous and reliable estimates is required for calibration of predictive formulations to be used in the framework of performance-based seismic design.