Holdfast Training Services Trial Blog

I have recently completed the area I was first working on and have now been assigned as the Site Engineer for vertical elements in the just started Residential Tower. From my first blog you would have seen Multiplex (MPX) fears over not winning this job and the congestion on site that would have caused. Well they needn’t have worried as they won the contract and have just started construction of the 80 story Residential Tower.

The system of jump form that has been selected is causing some excitement in the office, so I thought it was worth sharing with you here. It is apparently so innovative that most in the office have never even heard of it let alone seen it. Before we look at the new system it is worth just understanding how a traditional jump form works.

Traditional Jump Form Tower Construction

Traditional jump form systems form the core only, several levels higher that the decks. The video below shows the normal sequence for a core only jump form.

The foot print of the jump is normally only a fraction of the buildings and space is very tight at the top. Below is done pictures of the traditional jump system being used for the commercial tower on my site.

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The decks are then constructed using either structural form work (i.e. bondeck which provides form work initially and then becomes part of a composite slab once the concrete has cured) or traditionally using removable form work that is supported by a lattice of props and beams. Critically this leaves the columns to be poured separately once the deck is in place. Again this is normally done using a traditional form which must be set up individually for each column adding days of delay. To get around this on the commercial tower on my site are using hollow steel sections as form work then pouring concrete into them to create a composite section. Below is some more pictures of the commercial tower this time of the the decks being constructed.

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Oliver Moore (OM) Jump Form Tower Construction

This new OM jump form is radically different in that it covers the whole footprint of the building and allows the construction of all vertical elements simultaneously and at the same level i.e. the core, columns and shear walls all done at the same time and same level. When fully constructed the system also contains all structural and external façade works minimising the risk to workers and the general public. This is achieved by having a set of screens directly attached to the top of the jump which hang down 5 levels to enclose the horizontal structural works (in this case PT slabs).

From the bottom of the first screens a monorail system is connected which allows a winch system to manoeuvre around the whole of the building for façade install. This eliminates the risky use of mini crawler cranes that have to dangle massive glass panels over the buildings edge to get them installed. These works are similarly enclosed by a second screen system cantilevered from the first hanging down 2 levels. The connection to the primary jump system means both screens and monorail will move as the system does. When this happens an externally complete building will emerge from out of the bottom of the jump.

Multiplex have set an ambitious completion program that has been written into the contract. Once fully launched the jump has been set a 5 day cycle which means all steel work will have to be completed in 8 hours and post tensioning work completed in 4. I have yet to dig in to the program so don’t ask too many questions on this just yet.

The new jump system is also getting an extensive vertical transport system to support the cycle time. The movement of men and materials will be supported through a number of systems, three high-speed site hoists will be installed along with two tower cranes and an integral cantilevered jump lift. A single car site hoist will move through penetrations left open in the podium slabs before climbing the exterior while a double car site lift on the other side of the building will climb up the exterior of the tower from ground level. These hoists will be extended in line with the jumps to ensure quick access is always maintained to the top of the jump form. There is also a cantilevered integral materials lift that is connected to the jump system moving as it does, the lift will be used for the movement of  materials up to 5 levels down from the top deck. This is needed as normally the cranes would land materials directly on the decks but with the jump system covering the decks materials must be landed on the decks and subsequently transported down.

This is all shown diagrammatically in the images below however I suspect they won’t come up large enough to see the detail, so please click here to access the source documents.

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Hopefully that has been interesting and provided a snap shot of what I am up to. Please feel free to fire any questions you have at me and I’ll do my best to answer them. The jump isn’t on site yet so I’ll probably follow this post up in a few months once it’s running to give you some real pictures and let you know how it works in reality.