This educational video from AMSYSCO, Inc. shows the process for determining the Friction Coefficients.
Post Tensioning Institute (definitions):
- Friction Loss: the loss of stress (force) in a prestressing tendon resulting from friction created between the strand and sheathing during stressing.
- Wobble: the friction caused by the unintended horizontal deviation of the tendon.
- Angular Curvature: the friction caused by the profile of the tendon.
American Concrete Institute (ACI-318 Chapter 18, Table R18.6.2) gives ranges for Bonded and Unbonded post tensioning tendons. The lower the Wobble and Angular Curvature friction coefficients are, the higher the force per tendon. A higher force per tendon can help solve field issues such as broken tendons or under-elongations.
AMSYSCO, Inc. recently conducted a field friction test in 2009 for our 0.5″ diameter Unbonded Post Tension Tendon. We used the “load-cell” method (shown in the video) and our friction coefficients outperformed the recommended values given by American Concrete Institute. To request a copy of our results, please email us at info@amsyscoinc.com.
Copyright © 2009 by AMSYSCO, Inc. All rights reserved.
wht is the first thing required before post tension?wht is the last thing carried out after post tension?
Richard, I would recommend reading the Post-Tensioning Institute’s Field Procedures Manual for Unbonded Single Strand Tendons. The book goes through the entire post-tension process (Intro, Documents, Delivery/Storage, Installation, Concrete Placement, Tendon Stressing, Elongation, Tendon Finishing, Encapsulated Post Tensionn Systems, Jobsite Troubleshooting).
The Post-Tensioning Institute also offers a few courses on Field Certification for Ironworkers and Inspectors.