fib BULLETIN NO. 113

Title: Polymer-duct systems for internal bonded post-tensioning

Recommendation

Year: 2024

Pages: 171

Format approx. DIN A4 (210x297 mm)

ISBN: 978-2-88394-186-1

Abstract:

Thick-walled polymer ducts have been used since early 1990 for internal bonded post-tensioning applications. Based on the first ten years of experience, fib Bulletin 7 Corrugated plastic ducts for internal bonded post-tensioning was published in 2000. Since then, polymer ducts have found their way into several national standards and recommendations and are to be found on the market in various products (ducts and accessories) that differ in material and geometry details. The fib Bulletin 7 was updated and extensively amended in 2014 and published as recommendations in fib Bulletin 75. 

Since initially, experience with fabrication of these polymer ducts was quite limited, a number of system tests were specified not only for initial approval but also for factory production control during regular fabrication. This is in fact quite exceptional since approval procedures for post-tensioning systems typically specify material and geometrical checks for factory production control only (except single tensile element tensile tests). Now, another ten years later, and with significant experience gained with the fabrication of polymer ducts, time has come to adapt the factory production control procedures of polymer ducts to those typically used for post-tensioning systems. Hence, all system tests were removed from factory production control except one which verifies geometrical fit of duct and duct couplers which is difficult to verify by dimensional checks only. 

In addition to these changes to factory production control, the current content of fib Bulletin 75 has been mostly kept but critically reviewed and amended or corrected where necessary. Test procedures for dimensional requirements, and leak tightness of duct system and of anchorage-duct assembly have been modified in order to obtain a quantitative result from a pressure reading rather than a qualitative visual observation of leakage only. However, the actual performance requirement has not been changed, hence results of testing to fib Bulletin 75 can be considered still valid also under the now updated specification. 

We acknowledge the valuable contributions of all the members of Task Group 5.11 and the support of Christian Krebs as expert for questions regarding polymer material properties.

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