Abstract
The objective of this paper is to present proper finite element (FE) models which can predict the dynamic characteristics and behaviour of a railway bridge under dynamic train loading for the purposes of fatigue design and assessment. As a case study, an existing six-span continuous welded plate girder railway bridge in Stockholm having the cross beams oriented at a skew angle of 80˚ with the main girder is investigated. The bridge was built in the mid 1950s and its span vary between 26.9m and 33.6m in length. A number of detailed three-dimensional FE models of the bridge are developed in terms of increasing complexity, starting from a beam-only model and refining it to an FE model consisting of shell elements and the combination of the two. Additional factors that are being investigated are the effects of different boundary conditions, the number of modelled spans and the effect of secondary elements such as bracings. Eigenvalue analysis of the bridge is first carried out in order to determine its dynamic characteristics such as dominant frequencies and mode shapes. These are compared between the different models and the existing analytical solutions. Furthermore, available field measurements at different members on the bridge are compared with the results obtained from the FE analysis under the passage of a typical locomotive at various speeds. Based on the numerous FE analyses on the bridge models and their validation with the field measurements, few conclusions and suggestions are made for the advanced dynamic modelling of bridges.