Numerical modelling of the Vindel river railway bridge : upgrade of a finite element model from dynamic measurements

The Vindel river railway bridge is located outside of Vindeln. The bridge is a concrete arch bridge with a total length of 226 m. It was built in 1952 and was originally constructed to carry an axle load of 25 tons but has been classified to carry 22.5 tons until a couple of years ago when the allowed axle load was increased to 25.0 tons. In 1997 the bridge was investigated and cracks were found in the sections closest to the crown, movements were also noticed when trains passed by, which led to further investigations. The bridge has been the subject to two earlier reports, Bennitz (2006) and He et al (2005). Complab at LTU made measurements on the bridge and Bennitz evaluated these in order to find the eigenfrequencies and their correlating eigenmodes. He’s work resulted in FE-models with which he analysed the bridge. The purpose with this report is to continue where Bennitz and He left of and to continue the analysis in order to find out more about the dynamic behavior of the bridge. Creating a new FE-model and evaluating new measurements was a part of this but unfortunately the measuring was delayed and the analysis of those results will be presented in a report by Ola Enochsson. From the FEM-analysis that has been performed ten eigenmodes with frequencies up to 7 Hz was identified, the nine that Bennitz found and one more to add. The frequencies found are relatively close to the earlier measurements. The static deflections of the bridge have been simulated with Brigade using loads representing the heaviest test train, BV-3 in three different positions on the bridge. The initial deflection based on the self weight of the bridge was 8.3 mm and the largest deflections from the different train loads were 2.0 mm, 2.0 mm and 8.0 mm. The dynamic live load effect has also been simulated. For the dynamic analysis have the load from three different trains have been evaluated, the trains are BV-3, D-2 and the steel train. These trains have been simulated for velocities between 50-120 km/h with the interval 10. The largest deflections from the dynamic live load analysis are when the train is positioned covering half the bridge, and they are 8.3 mm for BV-3 in the speed 80 km/h, 6.6 mm for D-2 travelling in the speed of 90 km/h and for the steel train 6.5 mm at the speed of 90 km/h. The values from the dynamic live load compared to the values from the static live load test are almost the same as for the largest deflection. This indicates that the bridge does not swing with its eigenmodes for the velocities tested.Validerat; 20101217 (root