This short clip shows how to apply paint-marks prior to stressing of post-tension tendons. It’s recommended to use a straight-edge, metal to help with elongation measurements. Refer to the Post-Tensioning Institute’s “Field Procedures Manual for Unbonded Single-Strand Tendons” Chapter 7 for additional information.
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Copyright © 2011 by AMSYSCO, Inc. All rights reserved
As a post-tensioning inspector or installer, have you ever been in a situation whether you are unsure whether some PT tendons have been stressed? By not having a PT tendon stressed, this could have detrimental effects on the structure.
Here are three pointers that may help you out:
1. PAINT-MARKS : Compare the location of the paint-marks to other tendons of the same length. If you see a major difference in one or more paint-marks, then the flag should go up. If the location of the paint marks are similar, then either ALL of tendon have been stressed or NONE of them have been stressed. If you have a deviation, then you may have an unstressed tendons or an elongation issue. (Related Video :Applying paint mark for post-tensioning tendon).
2. BITE-MARKS : Check whether there are “bite-marks” on the tendons. During the stressing operation, the hydraulic jack “grabs” the stressing tail of the PT strand and and creates a series of small bite-marks. The picture below shows two tendons that have been stressed (click picture to enlarge). This visual inspection helps if your paint-marks have been washed away.
Bitemarks into Post-Tensioning Strand
3. ELONGATION RECORDING : AMSYSCO highly recommends that the inspector (or testing agency) record elongation during the stressing operations…rather than several hours later. This step increases the quality control of the project and eliminates a potential unstressed tendon.
– Neel Khosa, Vice President, AMSYSCO
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Copyright © 2011 by AMSYSCO, Inc. All rights reserved.
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.