The bridge survived 48 times more weight than expected - New Technology

Approximately 140 sensors were placed on the bridge to get as much data as possible. 36 pulleys with steel cables per jack anchored 24 feet into the rock face trial. Photo: Transport Administration

Load test on steel bridge in Norrbotten had a successful outcome. The bridge survived over 1 200 tonnes, although it was designed for 25.

For a layman seemed little difference on the bridge after the load, but överramsstången the truss closest to the camera is slightly skewed. Thomas Blanksvärd, investigators from Luleå University of Technology, and Anders Carolin, broexpert of Transport Administration, told the trial of journalists .. Photo: Transport Administration

Anders Carolina. Photo: Transport Administration

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bridge will be loaded until it collapses

The journalists present were perhaps a little disappointed that the crime was not more spectacular.

– Bridge just broke up quietly and slowly, and there was some creaking and crashing, says Lars Hedstrom, press officer at the Swedish Transport Administration.

– No comment “oh well, it’s clear now,” was enough, but it was a very clear violation of what occurred. And it bang a little and jumped backward, says Anders Carolin, broexpert the Swedish Transport Administration.

purpose of the load test, part of a larger research project, is to find out if it is possible to allow for higher loads on the Swedish railway bridges and let them be in use anymore.

bridge that was tested has previously been over Åbyälven in Norrbotten, but was moved before the load test to a place five kilometers north of Långträsk and placed on a concrete foundation. During Thursday morning was subjected to loads with large jacks that drew my part down to the ground.

– We managed to get into three different offenses in the design. First, there was a material breach when the steel began to flow, resulting in permanent deformations in several places on the bridge, for example in lattice structure and sekundärbärverket, where trains are running normally, says Anders Carolin.

But the bridge still could carry more cargo, so the trial continued. Then we had a break in a long beam under the jacks, as Dodge put together. However, scientists have continued to add more load.

– Since we reached the point where the bridge can not handle more cargo and then we got a vippbrott when överramsstången in truss snapped. After that, we continued to run with jacks but only got larger deformations, says Anders Carolin.

At most, passed the bridge over 1 200 tons burden, that is considerably more than the 25 tonne bridge were designed for the 50′s. The type of bridge has an overcapacity Clearly, then, after the trial, but exactly how big it is can not Anders Carolin answer yet.

– We need to look at the data first. The load today is static and applied slowly in a controlled manner, it should be translated into trains running at high speed with several coaches, he says.

There are four other railway bridges that are identical to the bridge that was tested on Thursday. One of them is on the Ore Railway, where LKAB transporting its ore, and the mining giant would gladly load of 32.5 tonnes. But yet, the Swedish Transport Administration not call LKAB and give the green light.

– No, but we do not have to leave and say “forget it”. The issue of running heavier trains includes much; rails, sleepers, fastenings and their own wagons, and is something that we have to investigate with them. But as far as the bridge, we should be able to have some feedback to clear this year, says Anders Carolin.

Now the old Åbyälvsbron and jacks dismantled. Some bridge parts will be recycled and some parts to the lab at Luleå University of Technology, to further load attempts to be made on certain details.

– It’s all about points and joints, riveted joints, to see how they look when they are loaded normally but also how they look when we impose very high loads. There are many uncertainties and conservative assumptions in terms of riveted joints, says Anders Carolin.