Research project DLM
Bridge dynamic; dynamic load model

Bridge dynamic; dynamic load model

Project name Bridge dynamic; dynamic load model
Acronym DLM
Project partner
Grantor DZSF (German Centre for Rail Traffic Research at the Federal Railway Authority)
Duration January 2020 to June 2023

Research field
(E+E > Energy + Environment
I+I > Information + Intelligence
M+M > Matter + Materials)
Project content
The Eurocode EN 1991-2, which was developed in the 1990s, regulates the load assumptions used for calculation of railway bridges. In particular, it defines the high-speed model trains HSLM-A and HSLM B, which are used for dynamic calculations of train crossings. Due to new vehicle concepts, new wagon lengths, bogie distances, and faster (freight) trains, the current model trains of the standard are not sufficient for the dynamic assessment of railway bridges. This leads to an urgent need to develop new load models that cover the innovations of the vehicle industry as well as operating trains. This was the aim of the present project, which was carried out by the international consortium AIT, REVOTEC, KU Leuven and TU Darmstadt.
The development of model trains for a new load model was based on a comprehensive collection of trains currently operating in Europe, which was compiled in close cooperation with vehicle manufacturers and based on axle-load measurement data. Relevant operational trains were derived from a collection of over 3000 passenger trains and 140,000 freight trains, considering possible future modifications of trains and applying DER- and LIR-spectra as well as the dynamic signature. The data from the vehicle manufacturers was also used to generate a data set of 25 multi-body models. In addition, a parameterised bridge set was defined using the bridge portfolio of German Railways (DB) and Austrian Federal Railways (ÖBB).
Using the data set of the multi-body models, extensive investigations on additional damping were carried out, which led to the conclusion that it is not possible to define a train-independent additional damping approach. However, validation by measurement-based system identification has shown that the multi-body models relying on information provided by vehicle manufacturers are suitable for dynamic calculation of bridge crossings. It can be concluded that the computation approach based on moving loads, which was used as the basis for the development of the new dynamic load models, provides a good approximation of the response resulting from a train crossing.
Using the derived relevant operating trains, over 20 million dynamic bridge crossings were simulated, and a load envelope was determined as a reference. The resulting envelope was then used for the derivation and optimisation of the desired load model trains, which include either conventional or articulated bogies. Finally, a load model for passenger trains (DLM-PT), a load model for freight trains (DLM-FT) and, with the use of an empirically derived reduction factor, a load model for light fast running freight trains (DLM-FT light) were developed and successfully validated on about 350 real railway bridges of different construction types and spans.
In addition, simplified methods based on a response spectrum and a meta-model for the estimation of dynamic structural responses for train crossings in the design process of a railway bridge were developed and validated successfully on real railway bridges.