Complete floors cast on ground
LIFT SLAB
SLAB TECHNIQUE
IFTEEN
New York
Farchitect, Philip Youtz and a Texas
oil-man, Thomas Slick, watched their revolutionary idea get off the ground with the first building to go up by the lift-slab method. In co-operation with the Southwest Research Institute at San Antonio they had worked for a year on an original approach to construction that would eliminate the seemingly wasteful need for erecting complex timber formwork before ac- tual concreting operations can begin.
The lift-slab method, in brief, con- sists of casting the roof and floors of a building on the ground and then later lifting these slabs into position by means of hydraulic jacks that are mounted on permanent columns. The slabs are cast one on top of the other in pancake fashion with a spray coat- ing of special curing membrane over each to keep them separated.
The earliest concrete structures to go up by this method were only one and two storeys high, but as the tech- nique was perfected it became pos- sible to "lift" multi-storey buildings into place by the same unusual and dramatic technique. Among the tall- est lift-slab structures is a 15-storey
This feature is contributed by Mr. Marshall Long, president of International Lift Slab Corp.. Overland Park. Kansas. Mr. Long states that the Lift Slab method is widely used in Aus- tralia and his corporation has been in correspondence with several concerns in the Philip- pines, Singapore, Hong Kong and Japan who have indicated an interest in introducing the system in South East Asia.
apartment building at Ann Arbor, Michigan, USA, and an 18-storey stock exchange at Sydney, Australia.
In
Prestressing the slabs provides ad- ditional advantages such as longer spans and deflection-free slabs. prestressed lift-slab construction, the slabs are cast on the ground over draped steel cables or tendons. These cables are then stressed with jacks and fixed into position after the con- crete is cured.
The combination of prestressing and casting on the ground minimises or eliminates the possibility of de- flection which would be particularly serious in lift-slab work. It produces thin slabs of great strength (greater than the ordinary reinforced slab), giving rise to a light and airy look in
Far East Architect & Builder August, 1966
Slabs in position on 15-storey block at Ann Arbor, Mich.
concrete in the form of wafer-thin horizontal layers supported and sep- arated by slim columns. Lightweight concrete, 110 lb. per cu. ft., can be used in lift-slab work to reduce load- ing on columns.
Basic Steps
Once the decision is made to em- ploy the lift slab method, the main concern of the builder is to plan his construction procedures so that the crucial stage of lifting the structure into final position can be smoothly and successfully completed.
Construction procedures using the lift-slab technique would, of neces- sity, vary with the size, height and
type of building that is being erected. Nevertheless, the following basic steps would apply to all lift-slab jobs:
1. Place the foundation.
2. Erect columns with special collar attachments.
3. Construct the slabs оп the ground, one on top of the other.
4. Lift the slabs by means of hy- draulic jacks placed on top of the columns.
5. Connect the slabs to the col- umns by means of the collar device.
Components
Foundation. The foundation for a lift-slab job may be either the ground floor that is placed directly over the
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