New Research Developments in the Assessment of the Damping Factor of Railway Bridges

Abstract

To achieve realistic and economical results, dynamic assessments of railway bridges require input parameters in mechanical models that accurately reflect reality. In this regard, the applied damping properties of the structure play a crucial role in predicting resonance effects and evaluating the compatibility between rolling stock and railway bridges. The EN 1991-2 standard specifies damping factors based on the type and span of the structure, but these values are often highly conservative and do not reflect actual conditions. As a result, in-situ measurements are often needed to reclassify bridges that appear critical in preliminary dynamic assessments as non-critical. However, determining damping factors from in-situ measurements often leads to variable results due to the measurement method used and the individual scope of action of the evaluating person interpreting the data. This contribution introduces new evaluation methods and analytical tools for determining damping factors from in-situ measurements, aiming to reduce the scatter of results and minimize the influence of the evaluator’s individual scope of action. Based on data from a measurement campaign on 15 existing railway bridges, this contribution discusses new evaluation methods for generating damping factors in both the time and frequency domains. The findings demonstrate that a well-defined evaluation algorithm can significantly reduce the scatter of results, and that the excitation method substantially impacts the determined damping factors. Additionally, the paper presents a novel approach for calculating the damping factor of railway bridges without requiring in-situ measurements. This mathematical determination of the damping factor offers a realistic alternative to overly conservative standards and enables a more accurate assessment of the dynamic behaviour of railway bridges.