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Presentation by Neel Khosa given during the Post-Tensioning Institute’s 2011 Technical Conference. Topic is about the use of unbonded post-tensioned concrete and stage-stressing PT girders in Target Field stadium, home of the Minnesota Twins MLB team.
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With some post-tension systems, the installer is required to strip the plastic-sheathing in order to install the intermediate anchors at the construction joints. One issue is how to protect the exposed strand until the second pour is made (pictured below – Pour #1 on left and Pour #2 on right).  Exposed strand at construction joint One solution is to put visqueen or a tarp on top of the bulkhead until the second pour is made. This has been specified by some Structural Engineers in order to protect the exposed strand from corrosive elements such as rain and snow. Another solution is to push the plastic tubes on to the backside of the bulkhead in the second pour (pictured below). This would provide added protection to the post-tension system at a lower cost than tarpping.  Strand protected by Tubing - Neel Khosa, Vice President _________________________________________________ Copyright © 2011 by AMSYSCO, Inc. All rights reserved.
Occassionally, the field will encounter a condition where the post-tensioned beam’s CGS (center of gravity of steel) requires several PT beams be installed in the slab. In other words, some PT anchors will not be installed within the web of the beam, but in the flange of the beam. Below are several pictures showing how these tendons can be installed at the jobsite.  Beam tendons sweeping out of beam  Beam tendons swept into slab  Beam tendons swept into slab at Anchors
It is recommended to add some #3 hairpins where the tendons curve to prevent blowouts in the concrete. Without hairpins, the tendon may “slice” through the concrete during the stressing operations. The tendon has a natural tendency to straighten out during the stressing operations. - Neel Khosa, Vice President _________________________________________________ Copyright © 2011 by AMSYSCO, Inc. All rights reserved.
Q: What does “AMSYSCO” stand for? A: “AMSYSCO” stands for American Systems & Structures Company.
_________________________________________________ Copyright © 2011 by AMSYSCO, Inc. All rights reserved.
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