Gulf Construction Online - Derrick crane to mall’s rescue

Germany & the Mideast

Liebherr cranes ... at Dubai Mall site.

Derrick crane to mall’s rescue

01 March 2009

THE region’s first Liebherr derrick crane — the 200 DR 5/10 Litronic — has solved a major problem for contractors at the Dubai Mall project by providing a solution to dismantle and remove a seemingly impossibly-located luffing jib crane.

“Without the derrick crane, it would have been physically impossible to dismantle a Liebherr luffing jib crane on the roof of the Dubai Mall and take it off site,” confirms a spokesman for the joint venture main contractor Dutco Balfour Beatty-Al Ghandi.
The Dubai Mall is one of the world’s largest shopping malls and forms part of the Burj Dubai district in Dubai. In preparation for the official opening of the mall last November, it was necessary to dismantle a large number of tower cranes employed throughout its construction.
To dismantle one such crane — a Liebherr 280 EC-H tower crane — it was necessary for the main contractor to temporally install a Liebherr 125 HC-L 6/12 Litronic luffing jib alongside the tower crane to remove its components. “The location of the luffing jib crane was such that there was no access even to use a conventional mobile crane technique. It would have been impossible to remove the crane without the Liebherr derrick crane, which is especially designed to dismantle tower cranes on high buildings,” explains a spokesman for its Germany-based manufacturer Leibherr-Werk.
Although designed primarily for high buildings, the derrick crane proved equally adept at removing the components of the luffing jib crane on the low-rise Dubai Mall.
“The solution for removing the luffing jib crane from the rooftop,” says the spokesman, “was to swing the dismantled components onto a 25-m length of rollers, allowing a Liebherr tower crane to lift them across a further 40 m off the rooftop. A second Liebherr tower crane was then utilised to carry the components a further 30 m, to be lifted in turn by a third tower crane and lowered to the ground for transportation offsite.
The Liebherr 200 DR 5/10 Litronic is designed to lift a maximum 10,000 kg but for the Dubai Mall application, it was been certified to lift a maximum of six-tonne load. “First for lift off was the six-tonne jib assembly followed by the A-frame counter jib without the hoist assembly, to comply with the six-tonne capacity restriction. With the cab weighing 10 tonnes, this too was broken into two elements,” the spokesman says.
Taking a day to install, the derrick crane was expected to complete the dismantling and removal within two days. The recently-introduced derrick crane, depending on its application, has been designed with load moments of 100 or 200 tonne-metres. Its supports are articulated and adapted to the structural circumstances of the substructure of the building to achieve optimum distribution of the support forces. Depending on the application, the crane can be used with or without supports, known as ‘shift legs’.
The dimensions and weights of all the individual parts of the derrick crane are designed to allow them to be dismantled solely with the aid of a small hoist and, on the Dubai Mall project, lowered to the ground in a similar sequence as the luffing jib unit.
The maximum dimension of the individual components was 2 m by 1.10 m by 1.10 m with a maximum weight per package of 1,000 kg. Throughout the construction of the Dubai Mall, no fewer than 29 Liebherr tower cranes were used, he says.
A fleet of Liebherr mobile cranes were also used throughout construction and fitting out prior to completion and handing over.