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RE: Elevated post-tensioned slab cracks

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Hi Gil,

Thanks for the clarification. Yes, even if the slab is UNcracked in service,
at higher levels of load (overload and failure conditions) where it will be
cracked it will behave as a 1-way system, in the way it was reinforced. My
point was that ACI 318 can only really call it a 2-way slab in the UNcracked
service range level of load, and beyond that it is 1-way.

Mark Geoghegan
Honolulu, HI

             > -----Original Message-----
             > From: Gil Brock [mailto:gil(--nospam--at)]
             > Sent: Thursday, January 09, 2003 5:56 PM
             > To: seaint(--nospam--at)
             > Subject: Re: Elevated post-tensioned slab cracks
             > Importance: High
             > At 03:14 PM 9/01/03 -1000, you wrote:
             > >I generally agree. The ACI 318 justification of PT
             > banded tendons as a 2-way
             > >slab only works if the slab stays UNcracked under
             > its service loads, or at
             > >or close to the balanced load, hence behaving as an
             > elastic plate.
             > I will even partly disagree with this statement
             > Mark. It will exhibit 2way
             > action at service if the slab is uncracked, but at
             > overload/ultimate
             > strength conditions it will be a 1way slab and it
             > will fail as a 1way slab.
             > Other cracks will appear that will make it look like
             > a 2way cracking
             > pattern but, as no reinforcement has been placed
             > across these cracks, they
             > cannot hold any moment capacity and the actual
             > failure strength pattern
             > will be 1way.  Though some of the PT experts in USA
             > seem to think
             > differently, a crack can only be controlled by
             > reinforcement across the
             > actual crack so reinforcement 15' away from a high
             > stress point will not do
             > anything to contain the crack width.

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