D-A-CH TAGUNG 2011 - SGEB

5 CONCLUSIONSIn the described study the dynamic behaviour of a multi span railway bridge has been investigated.Combining both numerical and experimental analyses with increasing complexity,respectively, the complex dynamic behaviour of the structure, that is charactarised by globaland local modes, could be well identified.The experimental modal analyses made a weak coupling of the actually statically separatedsuperstructures obvious. Fifteen global vibration modes of the bridge could be reliably identifiedfrom purely ambient acceleration signals, which were excited under wind and groundvibration. For these modes, the natural frequencies and mode shapes are accurately identified.The modal damping ratios identified from the second test campaign are generally of very low (< 1%).The finite element model properly predicts the first two global modes of the first span bothwith respect to shape and frequency. The third global mode of first span, known as the first torsionmode, was also computed for the FEM, but with a slightly different shape as identified fromthe tests. Furthermore it can be observed that the identified shapes of global modes of higherorder are very similar to several calculated mode shapes. However, more detailed investigationsare necessary for a correct assignment.Furthermore it could be proven that it is possible to identify multiple modes using two differentmeasurement systems if appropriate reference sensor locations are chosen. This meansthat the combination of independent measurement systems in practical applications under fieldconditions is capable.6 ACKNOWLEDGEMENTSThe research presented in this article was carried out within the European project FADLESS(Fatigue damage control and assessment for railway bridges), that was supported by the EuropeanResearch Fund for Coal and Steel (RFCS).REFERENCES[1] Deutsche Bahn AG. Richtlinie 804 - Eisenbahnbrücken (und sonstige Ingenieurbauwerke)planen, bauen und instand halten, 2010.[2] Deutsche Bahn AG. Richtlinie 805: Nachrechnung bestehender Bauwerke, 2010.[3] Österreichisches Normungsinstitut. ONR 24008 - Bewertung der Tragfähigkeit bestehenderEisenbahn- und Straßenbrücken, 2006.[4] Schweizerische Bundesbahnen. I-AM-EB: Richtlinie für die Beurteilung von genietetenEisenbahnbrücken, 2006.[5] B. Peeters and G. De Roeck. Reference-based stochastic subspace identification for outputonlymodal analysis. Mechanical Systems and Signal Processing, 13(6):855–878, 1999.[6] E. Reynders, M. Schevenels, and G. De Roeck. MACEC: A Matlab toolbox for experimentaland operational analysis. Report BWM-2008-07, April 2008.30812