Elastic Line of a Bridge: Methodology and First Test

14 Deck inclination and vertical displacements are among the most important technical parameters to 15 evaluate the health status of a bridge and to verify its bearing capacity. Several methods, both 16 conventional and innovative, are used for structural rotations and displacement monitoring; no 17 one of these does allow, at the same time, precision, automation, static and dynamic monitoring 18 without using high cost instrumentation. The proposed system uses a common laser pointer and 19 image processing. The elastic line inclination is measured by analyzing the single frames of a HD 20 video of the laser beam imprint projected on a flat target. For the image processing, a code was 21 developed in Matlab® that provides instantaneous rotation and displacement of a bridge, charged 22 by a mobile load. An important feature is the synchronization of the load positioning, obtained by a 23 GNSS receiver or by a video. After the calibration procedures, a test was carried out during the 24 movements of a heavy truck maneuvering on a bridge. Data acquisition synchronization allowed to 25 relate the position of the truck on the deck to inclination and displacements. The inclination of 26 elastic line was obtained with a precision of 0.01 mrad. The results demonstrate the suitability of 27 the method for dynamic load tests, control and monitoring of bridges. 28 29