Keywords: structural health monitoring, automated dynamic identification.

Structural health monitoring (SHM) is an emerging technology in civil engineering. Several applications are reported in the literature and several methods able to assess the health state of a structure exist. Some techniques aim at tracking changes in structural response directly or indirectly related to the mechanical characteristics (natural frequencies, etc.) during the service life and especially after damage due to exceptional loads. Alternative approaches are focused on post-processing of measurement data to detect anomalies. In both cases, the trend is to develop methods able to automate the detection process by exploiting recent advances in information technologies (IT).

As the first group of techniques is considered, one of the most relevant drawbacks is represented by the need of a user intervention during the structural modal parameters identification process. This specific aspect does not fulfil the requirements of SHM systems, which should be fully automated [1,2], in particular when several structures are monitored at the same time and distributed damage is expected, such as in seismic regions.

In the present paper, a proposal for automated modal parameters identification and tracking is reported. The algorithm herein described is set to tackle the above described drawbacks and can be integrated in a fully automated SHM system. It is based on a well-known technique of operational modal analysis, the so-called frequency domain decomposition [3], in both cases of blind identification and tracking of modal parameters.

The algorithm has been implemented into a specific software package developed in the LabView 8 environment and it is submitted to extensive tests. As a proof of concept, two case studies have been illustrated: the first is based on simulated data, while the second is based on actual data. The procedure seems to be able to correctly identify the modal characteristics of such structures, providing results similar to those of the finite element model (case 1: simulated data) or of the traditional single test identification (case 2: real records).

Future developments may lead to a software package which can be used for single tests, allowing a fast and reliable identification of modal parameters without any user interaction, or as modal information engine for automated modal parameters tracking procedures such as that one described in [4] which allows the estimation of such features in an automated way in a time shorter than the length of the recorded signals.

1

A. Mufti, "Guidelines for Structural Health Monitoring", University of Manitoba, ISIS, Canada, 2001.

2

S. Alampalli, "Influence of in-service environment on modal parameters", in "Proceedings of the 16th SEM International Modal Analysis Conference", Santa Barbara, CA, USA, 111-116, 1998.

3

R. Brincker, L. Zhang, P. Andersen, "Modal identification from ambient responses using frequency domain decomposition", in "Proceedings of the 18th SEM International Modal Analysis Conference", San Antonio, TX, USA, 2000.

4

C. Rainieri, G. Fabbrocino, E. Cosenza, "Automated Operational Modal Analysis as structural health monitoring tool: theoretical and applicative aspects", Key Engineering Materials, Vol. 347, 479-484, 2007. doi:10.4028/www.scientific.net/KEM.347.479

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