Mace has invested £9M in a radical new ‘jumping factory’ - a rapid construction method which will see buildings built at a rate of one storey a week.
“The aim is to achieve a 55 hour cycle so one week or floor, which will be the first time this is done since the empire state building,” said Mace project engineer James Rushton.
The self-contained factory is housed in a giant 10 storey ‘tent’ which is built around the perimeter of the new building. Inside, the building is constructed floor by floor and when one is completed, the factory is ‘jumped’ up 3.3m to the floor above to repeat the process, revealing the completed building below.
The contractor has rolled out the new technology to construct East Village Plot No 8, a 30 storey residential building in Stratford, London. The building has been designed with the innovative method in mind with as much off site and modular construction as possible.
“Once we’ve jumped, the process starts again,” said Rushton. “We lay the rebar, pour the slab, then we start putting in twin walls, standing columns then we come in with the bathroom pods and Hvac [Heating, ventilation and air conditioning] units. Everything is modularised so it all comes fully fitted.
“You get repeated quality, it’s safer for the workers, it minimises noise and dust for the surrounding environment, we can’t be rained off and the factory is rated up to a force 12 gale.”
The building itself is a precast concrete twin wall construction with a core at its centre. However, at each of its four corners the concrete columns have been replaced by steel columns. These twin UCs support the jumping factory as it makes its way up the building.
Inside the factory, a ring truss around the perimeter of the structure supports two 30t gantry cranes – actually four 15t cranes, tethered together in pairs, one situated over the loading bay and the other a working crane which ferries materials back and forth over the floorplate. Secondary trusses then support the roof and membrane walls.
In turn, the ring beam is supported by the 3.5t steel brackets which sit on 50mm thick, 500mm long plates welded to the steel columns at each floor level. Diagonal steel props are wedged between the steel columns and perimeter concrete columns to take the lateral load from the factory to ground.
To jump the structure, hydraulic jacks situated between the ring beam and the brackets activate and transfer the load of the factory into the bottom set of brackets. A 240mm pin is then removed allowing the top set of brackets to be lifted by the jack to the next support point on floor above. The pin is then replaced in the higher location to lock the structure in place, the jacks deactivated and load transferred back into the building’s frame. The bottom brackets then climb up the building to replace the previous position of the top.
“At the moment it’s supporting about 220t but when we’re jacking with resultant moments we get up to about 500t in each corner,” said Rushton. “It’s quite phenomenal that that’s all sitting on a 50mm thick plate.”
The process takes little over two hours.
To feed materials to the project, the team is applying a ’just in time’ delivery system, which at full pelt will see a delivery to site every 13 minutes. Goods are delivered to a loading bay on the north side of the site.
When the building is finished, the factory’s bespoke supporting steelwork can be modified to fit around other buildings.
Currently the team is constructing floor seven. Rushton said it was yet to hit full speed, but it was continually improving the design and was ironing out the logistical challenges.