Microwave remote sensing of bridges and large structures: advantages, limitations and possible applications

Recent progresses in radar techniques and systems have favoured the development of microwave interferometers, suitable to the non-contact measurement of vibrations on large structures. The main characteristic of the new radar systems is the possibility of simultaneously measuring the static or dynamic deflection of several points on a large structure with high accuracy. The objectives of the paper are: (a) to describe the main radar techniques (i.e. high resolution radar waveforms and phase interferometry) adopted in the radar-based measurement of deflections, in order to highlight advantages and potential issues of the new technology; (b) to illustrate the application of microwave remote sensing in static and dynamic testing of full-scale bridges and in the measurement of the vibration response of structural elements very difficult to access by using conventional techniques, such as stay cables.