LabVIEW toolkits for output-only modal identification and long-term dynamic structural monitoring

Abstract

This paper describes the development of computational tools for modal identification and long term dynamic monitoring in LabVIEW environment. These tools mainly consist of two individual toolkits for structural modal identification (SMI) and continuous monitoring (CSMI), respectively. The SMI toolkit implements the frequency domain Peak-Picking (PP) and Enhanced Frequency Domain Decomposition (EFDD) method, as well as the time domain Stochastic Subspace Identification (SSI) techniques. Based on this toolkit, the user can easily develop the whole process of structural modal identification by simply pushing buttons. The CSMI toolkit was conceived for continuous dynamic monitoring excluding manual interaction. It automatically searches the latest output measurements, detects maximum vibration amplitudes and makes statistical treatment of acceleration time series, generates waterfall plots for depicting the frequency component distribution and identifies modal parameters based on automated EFDD technique. The application of these tools is briefly described based on experimental data collected at Pinhão bridge and Coimbra footbridge.

Keywords:

• modal identification
• peak-picking
• enhanced frequency-domain decomposition
• stochastic subspace identification
• continuous monitoring

Acknowledgements

The authors acknowledge the financial support provided by the Portuguese Foundation for Science and Technology (FCT) in terms of basic funding of FEUP and research projects POCTI/ECM/46475/2002 and POCI/ECM/57286/2004, as well as the PhD scholarship provided for the first author.