Train-track-bridge interaction effects on highly skewed girder bridges of short-to-medium spans for increasing operating speeds

This paper contributes to comprehend the vertical vibrational response of oblique, simply-supported girder bridges on high-speed railway lines. Simplified methods adopted for dynamic analysis of such structures admit 2D beam-type models for the assessment of the Serviceability Limit State associated to traffic safety. However, in skewed bridges with multi-track decks and open sections, the dynamic response under railway loads is rather complex due to the coupled participation of three-dimensional modes. Based on experimental data from two existing bridges of different span lengths, detailed digital twins which include an explicit representation of the ballast track are implemented. Taking these models as reference, the influence of skewness on the modal parameters and maximum acceleration under passing trains is evaluated considering bridge variants. Correlation with the presence of transverse diaphragms at the supports and the restraining effect of the ballast track between spans is investigated as well. Finally, the adequacy of considering vehicle-bridge-interaction effects is assessed through numerical-experimental comparisons. The results reveal a reduction in maximum acceleration levels with increasing skewness and a notably weak coupling between consecutive spans, suggesting that classical single-span models may not always safely estimate the deck's maximum vertical response.