Dutch construction, mining and energy company Mammoet have aided a Finnish construction company in restoring a collapsed bridge in Umea, Sweden.
The bridge, weighing over 3,000 tonnes and being 464 metres in length, was being constructed using an incremental launching process, and it was during the second launching stage when trouble started according to Mammoet’s Sales Manager Rafael Martinez.
“The bridge moved forward in an uncontrolled manner for more than 130m, causing it to rest in an unstable condition,” he said. “Additionally, when the bridge dropped, the impact caused serious damage to the sections of the steel deck that were resting on the first two concrete piers. It also caused the bridge to twist out of alignment and the backend to fall from the abutment.”
Mammoet’s engineers were on the scene within a few weeks, however, with a salvage-solution already designed when they arrived. Further inspections carried out on the site confirmed that salvaging the bridge was the ideal scenario.
With concrete piers on the bridge that were “over 30 metres high”, the Mammoet team decided that operating at that height was neither “easy or safe”, resulting in the decision to cut the most damaged part of the bridge, pull the rest back to the launching pad, and then repair what they could at ground level.
To complete this, temporary shoring towers were placed around the concrete piers to release the bridge, whilst a cantilever gantry was used to lift the back section off the ground and raise it up to the launching level at the abutment, close to the launching pad. The realignment work was aided by hydraulic jacks atop each shoring tower.
“These could move the bridge up and down, right and left, and back and forth,” Martinez explained. “The system is computer-controlled, so we had constant, real-time monitoring of all the loadings of the bridge, meaning we could move it in any direction.”
Conceived in 1803, Dutch company Mammoet have gone through multiple mergers with other lifting and construction companies to become a global construction, mining and energy powerhouse.