ASSESSMENT OF THE PEDESTRIAN BRIDGE OVER THE DRAVA RIVER IN OSIJEK
On December 11 and 12, 2020, experimental measurements of the dynamic parameters of individual structural elements were carried out on the Pedestrian Bridge over the Drava River in Osijek.
As a part of the experimental measurements, the forces in the hangers on the upstream and downstream side of the bridge, the force in the main anchor cables were measured and the structural dynamic parameters were determined. The aim of the extensive field tests is to determine the dynamic parameters using the analysis of video recorded by the drone and their comparison with traditional measurement methods.
The traditional determination of the structural dynamic parameters (natural frequencies, damping coefficients and mode shapes) was carried out by measuring vibrations (with accelerometers) together with a system for collection and analysis. The procedure is based on the singular decomposition of matrices of spectral density functions measured at the vertical excitation of the structure by a seismic platform located on the bridge. Measurement of accelerations during forced excitations was performed on the downstream and upstream side of the bridge in a total of 100 nodes (50 on each side) in two perpendicular directions.
The recording of the bridge construction elements was performed by a multi-rotor aircraft equipped with a high-resolution camera and a laser measuring instrument (Light Detection and Ranging- LIDAR). Experimental determination of natural frequencies of anchor cables and hangers on the bridge was done by the method of motion detection of the excited element on the recorded video material and analysis of point cloudy in 3D space obtained by the LIDAR system.