Objectives: The paper analyses the vertical displacements of a railway bridge superstructure, steel-concrete composition, 50m span, under the the 250KN mobile axle load.
The running track of the bridge has a special structure: the rails are continuously fixed into the concrete slab using the Edilon corkelast 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.
Sixteen non-linear dynamic analysis have been performed with the 250 KN mobile axle that covers the analyzed model with speeds from 1, 10, 20, 30... 150m/s (3.6...540km/h).
Based on the results presented in this paper, we can say that, for the high speed trains that run at a speed that is close to 60m/s on this superstructure, it is possible that the vibrations and vertical deflections will be amplified. This amplification will be reached if the frequency with which the axles of the train get to L/2 is close to the own frequency of the first vibration mode of the analyzed structure.
The increase of the running speed of the mobile axle determines the increase of the amplitude of the vibrations, but this does not necessarily lead to a continuous increase of the recorded deflections of the superstructure.
The behaviour of the analyzed model from the point of view of the vibrations and of the deflection pattern corresponds to the known theoretical models.
The paper has a theoretical importance because it studies the behaviour of this type of structure in response to a single mobile axle.
KEYWORDS: superstructure vibration, mobile load, high speed, deflection
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