Broken PT Tendons

June 9, 2017

 

Post-tensioned (PT) tendons are structural elements in buildings. While broken tendons are not commonplace, they do occur. It can be a hassle figuring out what to do and how to approach the break. Although there are several different methods on how to accomplish the work, generally the structural engineer is first consulted on whether the tendon needs to be replaced. After review, the engineer often concludes the break is not severe enough to require repair. However, owners or builders may request the tendon be fixed regardless. (After all, who wants a new building with parts missing!)

 

Strand can be fixed many ways depending on the length and location. Sometimes couplers are needed to replace sections. Other times it is easier to replace the whole piece. PT requires a lot of specialty equipment and components depending on the repair such as PT couplers, stressing equipment, and new strand and anchors. The process includes scanning, chipping, inspections, and pouring back chipped-out areas. If several tendons have been broken, cut, or lost, shoring may be required.

 

When the tendon requires repair, sometimes the engineer will allow a smaller strand to be installed in place of a 0.5” strand because they may believe that the same size piece cannot go back in. This decision leads to two problems:

 

  1. A smaller tendon would leave room for moisture to collect which leads to rust and thus weakening the tendon. This has always been the number one downfall of PT.

  2. A tendon with more room will fly out unpredictably if it were to break or get cut in the future, potentially causing serious damage to person or property.

 

If tendons are installed to PTI standards, they can be replaced with the strand of the same size. When the tendon is tight, it is still free to move for stressing because of the grease. In this instance, if the tendon were to break, the grease would help slow its momentum, much more than depending on air resistance alone. Also, with less potential exposure to moisture, the tendon will last longer. Although the process is a little more complicated compared to smaller strand replacement, the result is a stronger strand with full forces.

 

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Post Tensioning Solutions

130 37th Street Northeast

Auburn, Washington 98002

(253) 737-5167

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