Abstract
Measurements of displacements of bridges under dynamic load are particularly difficult in the case of structures where access to the area under the tested structure is impossible. Then, remote measurement methods are preferred, such as interferometric radar. Interferometric radar has high accuracy when measuring displacement in the direction of its target axis. The problems appear when a bridge vibrates in two directions: horizontal (lateral or longitudinal) and vertical. The use of one radar to measure those vibrations may be impossible. This paper presents the application of a set of two interferometric radars to measure vertical vibration and horizontal longitudinal vibration with high accuracy. The method was positively verified by experimental tests on two railway bridges characterized by different levels of horizontal displacement. The accuracy of the radar measurements was tested by the direct measurement of vertical displacements using inductive gauges. In conclusion, in the case of vertical displacement measurements using one interferometric radar, the influence of horizontal displacements should be excluded. In the case of locating radars at the area of bridge supports, it is necessary to either use a set of two radars or first investigate the magnitude of possible horizontal displacements in relation to vertical displacements.
Highlights
The bridge displacement response is primarily sensitive to the stiffness of the bridge, whereas the acceleration response is affected by many other parameters, so bridge dynamic displacement is more suited than acceleration for updating railway bridge stiffness [2]
The presented method was positively verified by experimental tests on two railway bridges
In the case of a truss bridge with significant values of vertical and horizontal displacements, only the application of the set of two radars led to the conformity of measurements with the reference measurements
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Theoretical and experimental analysis of the displacements of bridge structures under static and dynamic load is important in SHM (structural health monitoring) or bridge load testing. With the developments of SHM systems, the deflection caused by the live load of bridges can be studied based on high-quality monitoring data from advanced deflection sensing systems [1]. The bridge displacement response is primarily sensitive to the stiffness of the bridge, whereas the acceleration response is affected by many other parameters, so bridge dynamic displacement is more suited than acceleration for updating railway bridge stiffness [2]. Accurate measurements of deflections are important in the validation of road bridge models [3]
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