Due to the increase in traffic load, steel railway bridge “Sava” in Zagreb was strengthened in order to meet higher standard requirements. After the strengthening, experimental investigation of the bridge was conducted. Bridge “Sava” is a double-track railway bridge over 4 spans with total length of 306 m and width of 9.6 m. Static system of the bridge is a simply supported continuous beam which is strengthened by the arch in the main span (langer beam). The main span is 135.54 m long and the remaining three spans are 57.50 m, 57.96 m and 55.00 m long. Static and dynamic loading was performed using two 119.5 m long train compositions each consisting of locomotive (4 axles, 20.0 t per axle) and 8 freight wagons (4 axles, 19.95 t per axle). During the static testing trains were positioned in different locations on the bridge in order to achieve maximal inner forces and displacements. Displacements were measured at 30 measuring points and strains were measured at 16 measuring points. Within dynamic testing, modal parameters of the bridge (natural frequencies and modal shapes) were determined using operational modal analysis during ambient excitation. In addition, natural frequencies were determined from vibrations measured with robotic total station after train compositions pass by at various speed. Experimentally determined displacements, strains (stress) and modal parameters were compared to the corresponding numerical values obtained from the FE model of the bridge. Values of experimentally determined parameters presented in this paper are important for future monitoring of the structural health of the bridge structure.

static and dynamic testing; structural health monitoring; operational modal analysis; modal parameters