In a first for Germany, Hochtief has successfully slid a new three-lane motorway bridge – nearly a kilometre long and weighing almost 30,000 tons – just over 19m into place beside its twin at the Lennetal Bridge on the A45 autobahn near Hagen in North Rhine-Westphalia.
A crowning achievement in the eight-year project to replace the old bridge, the pioneering manoeuvre was carried out to plan on Friday, 5 March after thousands of hours of planning by a team of 60 experts and a test-slide performed in Switzerland last year.
Some 90,000 vehicles cross the 30-metre-high bridge every day, and the slide was the final element of Hochtief’s strategy to keep traffic flowing as freely as possible throughout the project, which began in 2013.
First it built a temporary bridge to divert traffic from the old Lennetal Bridge, built in 1967. The old bridge was demolished by explosives in 2017.
Then it built a new, permanent, concrete and steel, three-lane bridge length to take traffic off the temporary bridge.
It built the piers for the second length, which adds three more lanes, but built that length on temporary pier structures 19.15m away from the first, so as not to disrupt traffic.
In the 6.5-hour operation on Friday, hydraulic winches hauled the offset bridge length with super-strong cables from its temporary piers to its permanent ones on tracks made for the purpose.
- See a video animation of the manoeuvre’s concept:
- And watch the pull on 5 March:
Hochtief described it as precision work; the length might have cracked if the pull was not completely even.
"We pulled the bridge simultaneously at 15 points. The tolerances were down to the last millimetre, and every step had to be perfectly executed," said Hochtief project manager Jan Felgendreher.
The project’s client, Elfriede Sauerwein-Braksiek, director of the Westphalia branch of state-owned Autobahn GmbH, said the technique could be used again.
"That the transverse sliding was carried out so successfully today paves the way for future construction projects," she said.
The six-lane bridge is scheduled to open for traffic in summer 2021.
Image: The operation took thousands of hours of planning by a team of 60 experts (Still taken from Hochtief’s video animation)