Dynamische Verformungsmessungen an Eisenbahnbrücken mittels Mikrowelleninterferometrie - Teil 1: Messverfahren

Dynamic measurements of railway bridge displacements through microwave interferometry - Part 1: measurement method

The microwave interferometry is a rather new measuring technique, yet little-known in civil engineering applications. It allows the non-contact acquisition of structural displacements with accuracy in the sub-millimetre range at a sampling rate of up to 4 kHz. The high sampling frequency allows also the caption of dynamic structural responses, which can be used for a straightforward determination of the main modal parameters of the structures (natural frequencies, damping ratios). Furthermore, the synchronous acquisition of the overall motion of the targeted object is possible due to a high range resolution, which facilitates a direct identification of modal shapes. This paper gives a short introduction of the measurement method and outlines its boundary conditions and limitations with respect to applications in railway bridge dynamics. The knowledge has been gained on the basis of comprehensive systematic experimental investigations performed within the frame of a cooperation project with the German Railways (Deutsche Bahn AG). As a result an evaluation matrix was created, which clearly illustrates the applicability of the microwave interferometry for different railway-specific tasks. The second part will present selected results of microwave interferometry measurements of railway bridges in comparison to parallel conventional measurements and the corresponding numerical investigations, which were used for the validation of the measurement technique.