Liebherr lifts large prefabs

19 July 2017

Dragages Singapore is using two high capacity Liebherr tower cranes to lift concrete prefabricated, prefi nished, volumetric modules for two 40-storey towers. The job comes as the Singapore government mandates this technique on some areas in the city.

Main contractor Dragages Singapore is using two Liebherr 1000 EC-H 40 Litronic High-Top tower cranes to erect the two 40-storey towers of The Clement Canopy, a condominium project that is the fi rst structure on the island to be constructed using an all-concrete version of the Prefabricated Pre-fi nished Volumetric Construction (PPVC) system.

Although this form of construction has been used elsewhere in the world, the project is the tallest ever to be built anywhere using concrete PPVC. These cranes are the heaviestlift tower cranes ever to have been imported into Singapore, having a lifting capacity of 40t at a working radius of 35m, and are top of the Liebherr 1000 EC-H High-Top range.

PPVC is a method in which free standing volumetric modules complete with fi nishes for walls, fl oors and ceilings are prefabricated and then erected on site. Singapore mandated PPVC for selected zones late in 2014, and is closely monitoring the use of this system as this method of construction is to improve productivity in construction sites.

Senior methods manager at The Clement Canopy, Kevin Lai, says that Dragages’ fi rst experience with this system was as far back as 2006, with prefabricated bathrooms for ‘The Sail’ condominium, a prestigious residential project at Singapore’s Marina bay area. In other recent PPVS projects, the company needed to lift steel-framed and hybrid modules, weighing less that 20t.

“This is the fi rst time in the world that full concrete PPVC units [have been] designed to build to 40 storeys.” Lai says during the planning stage Dragages and the architect, ADDP Architects, worked together to optimise the layout, dividing the residential units into modules and ensuring that one tower crane could be used to build each block.

In this way it was calculated that the heaviest module would weigh 29t, with the lightest at 17t. Dragages then looked into the crane market to see what was suitable.

Liebherr was selected from a shortlist of three companies for a number of reasons including lifting capacity, reliability, Singapore backup service, the technical support of the Tower Crane Solutions department in Germany and an attractive package. Another advantage, said Lai, is the size of the tower crane sections, which are smaller than those of the competing brands.

“The 2.4 x 2.4m size of the tower sections means that transport was easier, and also there is less room taken up on site.”

“We shall certainly consider purchasing if we have more work of this kind”, he said. “Singapore allows tower cranes to be used for only ten years, no matter what the brand, and so investments in this type of equipment have to take this into account.”

As this was the fi rst occasion that a Liebherr 40t capacity tower crane had been brought into Singapore, there was a lengthy and stringent approval process that had to be completed, taking around six months, before the cranes could be imported. They arrived in December and January, and took between four to fi ve days to erect on site.

Seng Swear Wern, civil production manager on the project, says that PPVC has allowed a reduction of the on-site workforce, but there are more people involved in the factory prefabrication. “As this is our first fully concrete PPVC job, and as we are still in the early stages, we are learning from our experience,” he says.

“This is very much a factory production line system. Certainly, in the long-term there is going to be a significant productivity improvement.” Seng explains that the concrete modules are being manufactured in Malaysia, and then trucked over the causeway into Singapore, where they are taken to the Dragages fitting-out factory at Tuas, on the far western side of the island.

Transformed into fully fitted modules, they are then taken by flatbed truck to the site. The largest of the modules measures 8.5m long by 3.2m wide and 3.15m high, complying with Singapore transportation regulations that stipulate a maximum trailer width of 3.4m and overall trailer transportation height of 4.5m. “Lifting the modules into place is very quick,” says Seng. “It takes only a few minutes to lift the module, but longer to do the precision placing. Placing has to be within ±2mm, because if there is any greater discrepancy, the entire building could become out of alignment.”

The Liebherr tower cranes are equipped with a Micro-move precision placing system, operated from the cab, and in addition Dragages has its own laser guiding system to ensure accuracy.

The operators are Dragages personnel, and have been provided with training by Liebherr Singapore. With a jib length of 35m, both of the cranes are able to operate from a fixed position outside of the two towers, and being tethered to a nonmodular element of the building, will grow as the structures grow.

There are in total 1,866 modules. Dragages in the early stages of the project is averaging the lifting of five modules per day, and is aiming to increase this to eight as the project progresses. The total lifting operation is programmed to take between 13 and 14 months.