Mainz, Germany-headquartered crane company Riga Mainz was commissioned by contractor Salcef Bau to lift out old bridge sections and install a new prefabricated rail bridge over a tributary of the Danube in Biberach, Germany.
For the job Riga Mainz used a 750-tonne Liebherr LR 1750/2 crawler crane. To ensure the crane, equipped with a 49-metre main boom, could work securely it had to first build a two-metre thick, 18×18 metre concrete slab. The slab was on eight large bore piles.
Due to confined space the assembly of the crane was challenging. Set up and dismantling took two days each. Company owner Uwe Langer, also responsible for project planning, reported, "The space conditions were very tight, as the newly constructed reinforced concrete bridges to be assembled were already placed on the construction site. In addition, we were restricted by surrounding trees."
Bore piles were also needed for the new bridge’s abutments. Drilling machines drilled 12 bored piles with a diameter of 1.5 metres and a depth of ten metres. After the lifting of the new bridge sections, they were cast with concrete into the abutments to form a ten-metre-wide and 20-metre-long new bridge structure. During this work the railway line had to be closed for five days.
The dismantling of the two old steel bridges, each weighing only 51 tonnes, went smoothly. The two prefabricated new reinforced concrete bridges, each weighing 285 tonnes, posed a more significant challenge. The LR 1750/2 had to move a gross load of 300 tonnes, including the crane hook block and rigging, to a lifting height of up to 27 metres and an outreach of up to 25 metres. Various auxiliary tasks for the crawler crane, such as lifting an 85-tonne excavator at a 42-metre outreach, were also performed. The entire job took just over two weeks (ten days of operation including five-night shifts).
