Comparison of Methods for Measuring Deflection and Vibration of Bridges

Continuous exploitation of bridges causes their progressive consumption. Periodic observations can help to control safety of such structures. Reliable description of behaviour of the bridge under load requires the use of method, which enables observation of many points simultaneously. The paper presents a comparison of deflection and vibration measurements performed on span of a steel bridge designed for tram traffic. Measurements were carried out during normal traffic. It was assumed to obtain the data necessary to determine the span deflection and vibration. Deflection measurements were carried out independently by two systems using different techniques: radar interferometry and digital image correlation. In both cases it is possible to measure many points on the structure simultaneously. Additionally, a set of accelerometers was installed on structure in order to measure vibrations. Vibrations were determined also by the ground-based interferometric radar. This novel measuring device operates on the basis of stepped-frequency continuous wave modulation and microwave interferometry technique. It allows to determine deformation and vibration frequency of the object through non-invasive observation of its behaviour at a frequency of up to 200 Hz. The authors present the comparison of test load results obtained by two systems and analysis of dynamics. * Corresponding author