New knowledge and increased understanding of older railway bridges and their possible lifespan can both be economically profitable and prevent accidents when the country's infrastructure is to be updated.
“If we increase the lifespan of existing structures, we contribute to sustainability by reducing the carbon footprint associated to demolition and building new structures. In this sense, new knowledge and increased understanding of what factors affect strength of older railway bridges is very important for our national infrastructure. Jacob and David have greatly contributed to this new knowledge creation, and we are very happy with the results” says Gabriel Sas, Professor and Head of Subject in Structural Engineering at Luleå University of Technology.
"Increased load concentricity, asymmetrical placement of loads on this type of bridge can lead to a disproportionately reduced load capacity. Concrete bridges are generally relatively old, the average age is 54.6 years, which can lead to an increased accumulation of damage and more serious damage in the foreseeable future," says David Åkergren, student within The Master Programme in Civil Engineering.
The work of the students has included a detailed modelling- and analysis process in the programmes GiD and ATENA Science where the behaviour of the model was calibrated according to test results obtained from a previous test of trough bridge called Lautajokki. After an appropriate behaviour was affirmed, the model was used in two separate studies. David Åkergren focused on the effect of load eccentricity while Jacob Gustafsson had his focus on the different models of load distribution through ballast.
"The hardest part of the work was to affirm that the model behaved like the Lautajokki bridge. It was an iterative process where support conditions and unknown parameters were changed one a at a time to get the behaviour as close as possible to the test result," says David Åkergren.
In the work, an analysis was also made regarding the current state of reinforced concrete trough bridges in Sweden. The database BaTMan (Bridge and Tunnel Management), owned by the Swedish Administration of Transport, was used to analyse for instance age and severity of current damages.
"Our long-term goal is that our work can contribute to a more accurate evaluation of the true capacity for bridges of this type. We hope that this can lead to an increase in life spans of these bridges and allowed axle loads on the Swedish railway network," says. Jacob Gustafsson, Msc. student within The Master Programme in Civil Engineering
A full-scale trough bridge will be tested in Luleå University of Technology's MCE laboratory shortly on behalf of the Swedish Transport Administration. Contact: Gabriel Sas, Professor and Head of Subject in Structural Engineering at Luleå University of Technology.