AMSYSCO Post Tension Blog

Updated PTI Specification Requiring Encapsulated Tendons

By admin, on January 19th, 2012

The following is a press release from the Post-Tensioning Institute which requires the use of Encapsulated Tendons for all unbonded PT buildings subject to ACI-318.

Release:

NEW PTI SPECIFICATION UPDATE REQUIRES THE USE OF ENCAPSULATED TENDONS

FARMINGTON HILLS, MI (January 16, 2012) – The Post-Tensioning Institute (PTI) has announced a new specification update approved by the PTI Board of Directors and the Technical Advisory Board. Addendum #3 to PTI M10.2-00 Specification for Unbonded Single Strand Tendons requires the following:

All unbonded single strand post-tensioning tendons used for structures designed in accordance with the Building Code Requirements for Structural Concrete (ACI 318) must be encapsulated. The encapsulation of the tendons shall be in accordance with the material requirements for aggressive environments in the PTI Specification for Unbonded Single Strand Tendons (PTI M10.2-00).

The intent is to augment the durability of the post-tensioning systems used for all applications governed by ACI 318. Encapsulated systems provide additional protection of the prestressing steel regardless of location of the structure or exposure to moisture intrusion from any source.

Addendum #3 to PTI M10.2-00 Specification for Unbonded Single Strand Tendons is available for free download on PTI’s website at http://post-tensioning.org/Uploads/Addendum3.pdf .

Source: http://www.post-tensioning.org/press_releases_details.php?id=21

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Missed Stressing Operation

By nkhosa, on December 18th, 2011

Q: What happens if you forgot to stress an unbonded post-tensioning tendon at the construction joint and have already poured the subsequent pour?

A: The most preferred option is to stress the tendon in the subsequent pour. However, the following items should be factored in:

a) The 7% Elongation Range must be revised.

Since you have a longer pull, the elongation calculation needs to be revised also. This should be noted in the elongation records from the PTI-Certified Inspector. A thumb-rule is to just add Min1+Min2 and Max1+Max2 together. For example,

First pull of 50′ would be Min1 = 3.72″ and Max1 = 4.28″
Second pull of 100′ would be Min1 = 7.44″ and Max1 = 8.56″
New elongation range for 150′ pull would be Min1 = 3.72″ + 7.44″ = 11.16″ and Max1 = 12.84″.
The new range is an close approximation. A more accurate range can be calculated with PT software. This is especially important for very long pulls.

b) The force in the tendon will likely be less.

Since the stressed tendon length is now longer, your angular and wobble friction have likely increased somewhat due to the increased number of spans. In other words, the final average force will drop in both pours for that particular tendon.

Previously, the 50′ pull may provide 27.5 kips of force in Pour #1.
Previously, the 100′ pull may provide 27.3 kips of force in Pour #2.
Now, the 150′ pull may provide only 26.9 kips of force in Pours #1 and #2.

c) The intermediate anchor has been abandoned.

The force within the 150′ tendon will be transmitted uniformly through the construction joint. Conversely, the 50′ tendon transmits force only within Pour #1 and the 100′ tendon transmits force only within Pour #2 (i.e. the construction joint “locks-off” the force within each pour). This is important should be there be any repair/renovation conducted in the future.

- Neel Khosa, Vice President, AMSYSCO

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Scholarship for College Students – Post Tensioned Concrete

By admin, on November 10th, 2011

PTI AMSYSCO Scholarship Program

The new PTI AMSYSCO Scholarship program has been recently established by AMSYSCO, Inc. to commemorate the company’s 30 years in the post-tensioning industry. In announcing this new scholarship program, AMSYSCO owner, Rattan Khosa said

“Last week AMSYSCO completed 30 years in business. Only in this great country America, one can come with just $8 and later start a business in a basement. Over the years, I have been returning to the community, part of what I make every year, through my private foundation named after my parents. I thought it was time that I did something for the post tensioning. It will be great to award scholarships through PTI.”

The AMSYSCO Scholarship will provide two engineering students with $2,500 each for the Winter/Spring 2012 school term.

The student must attend an U.S. engineering undergraduate or graduate program with preference given to those attending the University of Maryland, and the University of Illinois at Urbana, IL.
The student is required to be in good standing academically and must be pursuing a civil and/or structural engineering degree.
Preference will also be given to students studying and/or researching in the field of post-tensioned concrete.

Award recipients will be selected and announced March 30, 2012. In addition, the award recipient will be honored at an awards ceremony that will be held in conjunction with the Post-Tensioning Institute’s 2012 Annual Technical Conference.

The student will be invited to attend the conference and awards presentation at PTI expense. Please refer to information below to apply:

These forms are also available in Microsoft Word file format. Contact PTI and request the 2012 PTI AMSYSCO Scholarship package

Application deadline: February 29, 2012

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The content of this post is provided from the Post-Tensioning Institute. The scholarship selection process will be managed by the Post-Tensioning Institute.

http://post-tensioning.org/student_competitions.php

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