An interferometric radar for non-contact measurement of deflections on civil engineering structures: laboratory and full-scale tests

Abstract

Recent progress in radar techniques and systems has led to the development of a microwave interferometer, potentially suitable for non-contact vibration monitoring of civil engineering structures. The main characteristic of the new radar system, named IBIS-S, is the possibility of simultaneously measuring the (static or dynamic) displacement at several points of a structure with high sensitivity. The paper first describes the technical characteristics of the microwave interferometer and the results of laboratory tests carried out to evaluate the actual displacement sensitivity of the equipment. Subsequently, the application of the sensor to the measurement of ambient vibration response on a concrete bridge is presented and discussed.

Keywords:

• ambient vibration testing
• bridge
• interferometry
• output-only modal analysis
• radar

Acknowledgements

The research was supported by the Italian Ministry of University and Research (MIUR) under grant Cofin 06. The authors are indebted to the Local Administrations of Bergamo and Milan, owners of the bridge investigated. Furthermore, M. Antico, M. Cucchi, Dr N. Gallino (Laboratory of Vibrations and Dynamic Monitoring of Structures, Department of Structural Engineering, Politecnico di Milano) and Dr P. Ricci (Ingegneria Dei Sistemi, Pisa) are gratefully acknowledged for their assistance in conducting the field tests.