Monitoring of oscillations and frequency analysis of the railway bridge "Sava" using robotic total station

摘要

Bridges as a civil engineering objects are critical components of infrastructural system of every country. In order to verify design prediction and capability of taking over the design load, bridges are subjected to load testing, during which intentionally provoked displacements are measured. This paper presents implementation of surveying methods in dynamic testing of the railway bridge after reconstruction. Bridge Sava” is a double-track railway bridge over the river Sava in Zagreb. The bridge is a steel structure with total length of 306 m and width of 9.6 m. It consists of 4 spans, 135.54 m long main arch span and three girder spans 57.50 m, 57.96 m and 55.00 m. During the testing bridge was excited by two trains passing at speeds from 20 to 75 km/h. Vibration of the bridge was measured by accelerometers at 42 measuring points and by two models of robotic total station with measuring frequency 10 Hz and 20 Hz at measuring point placed in quarter of main span. This paper is focusing on the ability of total stations to measure the vibrations to the order of a few millimeters, as well as determining the natural frequencies of the bridge. Measurement results are compared to theoretical results, obtained from numerical model of the bridge and to result of Operational Modal Analysis based on acceleration measurements.