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How to replace a motorway bridge
This could be an exam question in civil Engineering: We have a 1 kilometer long bridge over land on a highway that 90,000 vehicles pass a day … How do we replace it without stopping the traffic, with the lowest possible cost and once finished, it has to be in the same starting position?
Although data is lacking for this «Mini exam» and, a prior, you can imagine some coherent solution. Few will guess how the little riddle turned out.
Engineering alone is amazing enough! But when you combine it with civil engineering, things get bigger than blunt.
In this story, the Lennetal bridge of the A45 motorway located in Germany. 30 meters high and almost a kilometer long, with thousands of cars and trucks that pass through its roads every day.
Since its inauguration in 1967, each year has seen its road traffic until reaching the 90,000 Vehicles per day. With so much effort, it was no longer viable to continue maintaining it.
The need to replace the entire bridge has launched a historic engineering milestone in Europe. From the Hochtief company, have managed to move - in one piece - almost 1 kilometer of three-lane highway with 30,000 tons of weight, a little more than 19.50 meters.
They move 19.5 meters a highway bridge with a length of 1 kilometer and 30,000 tons (three times heavier than the Eiffel Tower)
We better see it in the video …
The The operation carried out by the engineers to cover this section took 6.5 hours. Hydraulic winches with super steel cables moved the bridge into the correct position, insane!
Although you already have the solution of "exam". Today, we want to learn more, and for all of us who are not familiar with the techniques of replacing bridges, nor are we from roads or civil engineering engineers, I find the work they do surprising! we add a small diagram of how the replacement of the Lennetal bridge was carried out
1.- Build a new lane
Without stopping the traffic. The engineers' first step was to build a new four-lane road next to the old highway. This new construction will be - as we will see later - a transit direction for the future new highway.
As a small paragraph, remember that we already have the first robot that builds a bridge on its own, even if it looks like a toy, we can already see what the future will be like.
2.- We move traffic to the new road
When we have the new road finished parallel to the old highway. We pass the road traffic - both ways - to circulate on the new road and have the old lanes free.
We continue without obstructing traffic, although obviously we will have fewer lanes.
3.- Demolish the old highway
We have the old highway without traffic. We began the demolition of the two directions - six lanes - at the same time we began with the new foundation that will support the new highway.
In this particular case, the foundation is built independently and to support; three lanes in one direction and three in the other. Remember our article on building foundations with some very interesting injury files.
4.- Construction of only one motorway direction
On the new foundation that we already have. We are only going to build three lanes with one direction. With the intention of taking advantage of the new road that vehicles already circulate.
It is time to pass the road traffic of the first new highway built, to the latter that we have executed. Now, the first one, we already have it free of vehicles.
5.- Move the bridge with hydraulic winches
With the hydraulic winch system we move the one kilometer long bridge to place it in the original position of the old highway.
And we have everything in place! Although this may seem like an operation that is done in a short time. This project began in 2013, and at the beginning of this month, it is when the movement of the bridge has taken place.
For those who are more curious. We leave you the following video that details with 3D modeling how the entire process has been carried out by the engineers.
Civil engineering is passionate, but when it comes to bridge building techniques, it increases exponentially! Curiously, the longest road traffic bridge in the world is the 55 km long Bang Na Highway in Thailand. The construction of the huge bridge required more than 1,800,000 cubic meters of concrete.
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