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Early form release for two-way slabs
- To: <seaint(--nospam--at)seaint.org>
- Subject: Early form release for two-way slabs
- From: "Keith Pabst" <kpabst(--nospam--at)ha-pa.com>
- Date: Wed, 7 Apr 2004 08:44:45 -0400
I am working on a
project which has a 12 " thick, two-way flat slab system. The contractor is
proposing to use a forming system that offers an early release of the beam and
girder forms. The way the system works is there are shores at 6'-0" on
center each way with a beam and girder system supporting the plywood at 16 or
24" o.c.. The forming manufacturer has made recommendations for an early release
of the beam and girder system but leaving the vertical supports in place until
the concrete has reach the required strength. They have a one day release time
specified for a 12" slab as long as the min. compressive strength is 500 psi.
Basically they consider the slab to be a 2-way slab supported at 6'-0" o.c.e.w.,
unreinforced. They have analyzed the slab based on the modulus of rupture to
determine the early release time. I have looked through the ACI Manual
and have only found the section which requires forms for horizontal surfaces to
remain in place until the concrete has reached 70% of the required
compressive strength. I guess I have the following
this type of early release system
allowed per code.
2. Is the method of
analysis described above acceptable per ACI utilizing the modulus of
3. Can anyone point me to a portion of the code which
would allow such a system to be used without achieving the 70%
I would appreciate
any information anyone could provide
me regarding this matter.
Keith E. Pabst, E.I.T.
Highland Associates, Ltd.
Architects Engineers Interior
102 Highland Avenue
Clarks Summit, PA 18411