Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

278 Chapter Nine
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Jump Form System
In conventional gang forming, a crane serves two purposes: lifting
and supporting. Only a small fraction of that time is spent in productive
lifting. Most of the 15 to 20 minutes that a crane spends cycling,
a conventional gang form goes into idly supporting the form. Jump-
Form, the trade name of Patent Construction Systems, is a forming
system that dramatically reduces the crane time. It is used for gang
forming successive vertical lifts including shearwalls, core walls,
piers, battered walls, lift stations, and control towers.
The JumpForm system eliminates the supporting function, reducing
crane time to as little as 5 minutes on a typical lift. This is accomplished
by two unique features, gangs that tilt back and an automatic
release/attach device. JumpForm’s gangs retract, allowing workers to
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conveniently mount the next lift’s landing brackets while the Jump-
Form remains securely supported on the wall. This provides a clear
advantage over conventional gang forms, which must be fully removed
from the wall by the crane, before mounting the landing brackets.
JumpForm’s unique release/attach device works in conjunction
with the landing brackets to eliminate the need for any additional
wall attachments. All ties can be released, the gang stripped, and
other preparations made before attaching a crane. Once the crane is
hooked up and begins lifting, the mechanism automatically releases
the JumpForm from the wall, then automatically engages at the next
lift to fully support the system. The crane is released immediately
and preparations begin for the next pour.
An entire lift of JumpForms can be flown and secured in rapid
succession. Safety is improved because the release/attach mechanism
operates remotely; therefore, workers do not need to be on the system
to affect either the final release or the reattachment.
Workers can quickly bring gangs to a near true vertical position
by adjusting the braces to a reference mark noted from the initial lift,
as illustrated in Figure 9-48. Transit crews guide only the final adjustment
of the pipe braces, which saves time compared to the wedges
and stand-off jacks used in conventional gang forming. The pipe
braces minimize bonding resistance by effectively peeling the gangs
away from the wall for easy stripping. As the gangs retract, inserts for
the next lift becomes accessible from the JumpForm system’s upper
level work platform. Workers can now mount the landing brackets
before releasing JumpForm from the wall, an especially convenient
feature when constructing shearwalls.
Workers can mount the next lift’s landing brackets on both sides
of the wall while the JumpForm system is still in place. This minimizes
crane operations because the forms stay on the wall throughout
the formwork phase. Because JumpForm does not need the
support of intersecting floors, it is well suited to the construction of
tall bridge piers and similar floorless structures.
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