PERFORMANCE CONSIDERATION OF DYNAMIC CALCULATIONS ON AN UPDATED MODEL OF AN EXISTING BRIDGE

In fatigue calculations of steel structures, it is well known that the cyclic stress levels and therefore the
best possible determination of the actual stresses have significant influence on the result of the analysis.
Within the Rail4Future project, an existing railway bridge was investigated in more detail due to this
problem. The object of interest is a riveted truss bridge which is more than 100 years old and already
shows various signs of deterioration. Due to the given fatigue aspect, there is a high demand to accurately
calculate the stresses for passing trains.
Therefore, a 3D FE model was created and adapted to the actual boundary conditions (support, node
stiffness and damage) in a static model updating. This was only possible with a sophisticated monitoring
system – which consists mainly of strain gauges in combination with a Weigh-in-Motion system, to
identify the passing trains. In addition, dynamic tests and measurements were carried out to identify
eigenmodes, natural frequencies, and damping parameters.
Under the consideration of performance and resource efficiency, the updated and given model can be
used for dynamic calculations of train passages by various methods. In particular there are dynamic
computations by means of modal superposition, full transient computations, as well as transient computations for a single passing load followed by a superposition for all train axles. Another Aspect of interest
is, if there can be reasonable results for the model updating by the much simpler approach defined only
by a target function aiming at the measured natural frequencies of the construction.
By comparing the performance for the different calculation methods, the aim is to show where the best
approach in consideration of performance and resource efficiency is located. With the use of more
performant methods of calculations, resources and time can be saved in future computations.