Greater demands will be made in the future concerning traffic volumes, axle loads and speeds by rail, not least because of the "mining boom" in Northern Sweden. In a new doctoral thesis at Luleå University of Technology (LTU) the ability to increase the loading capacity for railway bridges has been investigated, which is an important part to meet the requirement.
- I have developed a new methodology with which one can assess the bearing capacity of concrete bridges with much greater accuracy than before and I've found that many rail bridges can withstand higher axle loads than today, which means significant savings, says PhD Arto Puurula at Luleå University of Technology.
His thesis is part of the EU-funded project Sustainable Bridges in which LTU was the scientific leader of 32 participants from 12 countries. In his research, Arto Puurula used a railway bridge in Örnsköldsvik as an experimental object. It has two spans and was reinforced with carbon fiber rods to test their effect on resistance. The bridge was closed in 2006 and was made available for LTU's research.
Arto Puurula has by computer programs developed models that can calculate how bridges behave as load increases. In a full-scale experiments on the railway bridge in Örnsköldsvik the researchers has placed a steel beam in the middle of the bridge span and with the help of cables pulled it down until there was a break in the span. But to not study the same as previous research has mapped closely on bend fracture, the researchers has reinforced the bridges edge beams with carbon fiber rods to get a so-called shear failure.
- I have analyzed the bridge in several ways and has for example measured the bridges deflection and stresses in the concrete and in the steel and carbon fiber reinforcement, says Arto Puurula.
He has in his calculations used a refined finite element model to evaluate how sophisticated computer programs can describe the real scenario when a bridge is loaded.
- With a refined and calibrated model, one can see how much you can increase the load on the bridge while maintaining safety, he says.