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Re: Time Constraints on Stressing Post-Tensioned Concrete Slabs

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In which PTI publications are the relations you are mentioning?

Juan C. Gray

Ed Workman wrote:
> 
> 
> 
>      -----Original Message-----
>      From: Gil Brock <gil(--nospam--at)rapt.pcdc.com.au>
>      To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
>      Date: Wednesday, July 28, 1999 9:17 PM
>      Subject: Re: Time Constraints on Stressing Post-Tensioned
>      Concrete Slabs
> 
>      The 3000psi figure for full stressing of a tendon is based
>      on the capacity of the anchors in bearing/bursting. If you
>      wish to use a lesser strength, you should only do it for
>      anchorages tested and certified to work at the lower
>      strengths. Some unbonded anchorages are rated as low as
>      2300psi.
> 
>      By the PTI expression, a slight modification of the
>      expression that used to be in ACI 318,  the minimum required
>      strength is calculable and is similar to ACI criteria for
>      bearing stress in that it is a function of the ratio of
>      bearing area to concentric concrete area. In that context
>      "tested and certified" is not germain to individually
>      anchored tendons common to building work. Where it is
>      desired to achieve early stressing such as at 1200-1500 psi
>      most anchor castings can be augmented with steel bearing
>      plates. It is a simple matter to verify the capacity of the
>      system via first principles.
> 
>