Application limits for continuously welded rails on temporary bridge decks

The possibility of omitting rail expansion devices from the track configuration, when continuously welded rail is continued over temporary bridge decks, is investigated in detail. More specifically, the related rail track to temporary bridge interaction phenomena are analysed using finite element modelling. A first parametric analysis assesses the additional rail stresses due to moving trainloads and temperature variations, based on stipulations provided in the unit identification code 774-3R. In addition the model is expanded to a more complex structure that is able to simulate the buckling behaviour of the rail track using non-linear methods. Using this model, a second parametric study is performed in which only thermal loading is considered. This allows for determining the parameters, which are predominant in determining the critical buckling temperature of the rails, and for assessing the magnitude of the safety margin necessary, when it comes to thermal buckling of the rails and the temporary bridges. It can be concluded that, depending on the magnitude of two main factors, the lateral ballast resistance and the amplitude of the initial track misalignment, a considerable reduction of the track stability might arise. Therefore, a minimal characteristic lateral ballast resistance of 4 kN is recommended along with a maximal allowable misalignment amplitude of 7 mm has to be prescribed when thermal track buckling has to be considered in the design.