Advantages and Disadvantages of the Counter Deflection Based on the Average of the Deflections Recorded in the Sections of the Superstructure of a Railway Bridge

Objectives: The paper analyses the vertical displacements of a railway bridge with a special shape of counter deflection, steel-concrete composition, 50m span, under the action of a high speed train. Work method: The running track of the bridge has a special structure, without ballast bed, with rails continuously fixed into the concrete slab using the Edilon material. In order to determine the impact of the increased speed upon the vibrations and deflections of a mixed section railway bridge superstructure, this superstructure has been carried into the SAP2000 finite element calculation programme. Two variants of superstructure have been analysed, one without counter deflection and one with counter deflection, based on the average of the deflections obtained in the bridge that had a straight running track. Twelve non-linear dynamic analyses have been performed for each model, with the Thalys train that covers the analyzed models with speeds: 1, 10, 20...110m/s (3.6...396km/h). The maximal value of the counter deflection is 10.323mm. Conclusions: The paper presents comparatively the deformations and vibrations obtained under the action of the Thalys train running with the above-mentioned speeds for two analyzed superstructures. The superstructure with counter deflection made up of the average deflections has a better behaviour (lower vibrations), for speeds higher than 90m/s.