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RE: CONC - Stripping of Deck Forms

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Bruce:

Given staging (construction live loads) and dead loads, you can
calculate the required strength, and other material properties.  Require
sets of confirmation cylinders to confirm the material properties.
Don't forget to provide for a standard deviation to your required
strengths.  This is similar to the f'cr as opposed to the f'c.

You can also consider reshoring which is a common practice, but don't
forget to consider the change in shears and moments due to the presence
of shores.

This is a common practice in high rise construction, especially with
flying forms.  The forms are dropped, rolled out and placed on the top
deck.  The number of levels with shores, and the number of levels with
shoring are determined by a structural engineer.  It is also a common
practice in post tensioned slabs where you do not wait for 28 days to
post tension a slab.

Often this is a separate contract for construction sequencing that the
contractor has with a structural engineer, it may or may not be with the
EOR.  Although it is wise to submit it to the EOR for approval.
Caution: this can be considered methods and means.  It will entail added
liability.  You should get more fee for this service.

Regards,
Harold Sprague
Black & Veatch
 ----------
From: PRSE(--nospam--at)aol.com
To: seaoc(--nospam--at)seaoc.org
Subject: CONC - Stripping of Deck Forms
Date: Wednesday, August 13, 1997 9:08AM

I have a project in Santa Monica, which is 3 stories of wood over a
structural concrete deck over parking.  The deck is specified as 4000
psi
concrete.  The contractor wants to know if he can strip the forms after
7
days, assuming the concrete has reached full design strength.  I am
hesitant
to let him do this because I am afraid the concrete will not be quite
cured
enough and the early removal of the forms may result in some
deflection/creep
problems.  As an alternate he has offered to reshore at 7 days with
posts
spaced further apart than the original shores.  His goal, of course, is
to
save money by returning the rented shores as soon as possible.

Any thoughts and/or experience with this issue would be much appreciated
as
they are scheduled to pour on Friday and are looking for an answer from
me
shortly.

Thanks in advance for your advice / opinions.

Bruce Resnick