German bridges fall to Atlas Copco breakers
By Lindsay Gale13 October 2011
One common characteristic of road bridge demolition is the limited time that is available to contractors to carry out the work in order to minimise disruption to traffic.
German contractor Prangenberg & Zaum faced just such a challenge when it had to remove a bridge on the A40 motorway at junction 28 at Gelsenkirchen-Süd for main contractor Strabag AG Koln in order to make way for road widening works in just two days. Using three Atlas Copco breakers - a 7 tonne HB7000, a 5.8 tonne HB5800 and a 2.5 tonne HB2500 - the solid reinforced concrete bridge and bridge heads were removed in just 32 hours. The resulting debris was processed by a pulveriser on site and then transferred to Prangenberg & Zaum's recycling station for further processing. In all, 2,300 cubic metres (88,300 cubic feet) of concrete and reinforcement were processed in this way.
According to P&Z site manager Holger Schmidt: "The work went off without a hitch. Our Atlas Copco hydraulic breakers worked as reliably as they always do. We are very pleased with a total of eight Atlas Copco breakers among our machinery. They never let us down, particularly on construction sites with tight deadline constraints."
The A40 is the busiest motorway in the Rühr, with 120,000 vehicles using it around the city of Bochüm at peak times and work began on widening it into a six lane highway in 2010 and should be completed in 2012.
Meanwhile, transport authorities in Germany had decided on some major road construction near the town of Lorch, Hesse, where the B297 road crossed over the B29 on a 3,000 tonne, two bay, reinforced concrete bridge. This bridge had to be removed as a part of the reconfiguration of the road layout but its design and geographical environment meant that it was a challenge for FWA Fischer, the demolition contractor assigned the task of removing it.
First, the B297 bridge had to be removed without any damage being caused to the carriageway of the B9 below. It also featured not only a longitudinal and transverse slope but also a curvature with a 280 m (919 ft) radius to the horizontal. In addition, a local access route that was slightly offset and 15 m (50 ft) below it had to be kept open for emergency vehicles at all times.
The above required that Fischer develop a demolition plan that described every single demolition phase in precise detail to ensure that work was carried out in a controlled manner that never put personnel, machines or the environment at risk. The works began with the complete closure of both roads and the removal of crash barriers. An impact bed was then laid on the B29 carriageway, using recycled materials, to act as protection.
Fischer then started work on the demolition itself, using a mix of tools (five Atlas Copco breakers and four Atlas Copco CombiCutters) which were mounted on a Cat wheeled excavator and five Cat tracked machines. Fischer simultaneously broke up the bridge deck from above and removed the bridge caps. The 4 m2 (43 ft2) concrete bottom chords were then demolished. Once the longitudinal reinforcements were accessible, they were cut into lengths and removed, and finally the bridge abutments were demolished. All concrete debris was conditioned on site and crushed so that it could be used as fill on other road projects.