PT Strand relaxation test 2

[Hunter707]

When conducting the relaxation test according to British or European standard, the initial load for the relaxation test should be 70% of actual breaking load.
However, when conducting the test according to ASTM or JIS (Japan), the initial load should be 70% of nominal breaking load.

Does anybody know the reason for the difference (why actual breaking load would be used in Europe compared to nominal breaking load in USA / Japan)?

 

[amsysco]

Hunter707, I don't have an answer, but that may a good question for one of the testing labs (CTL or Wiss Janey, etc.)

I'm not sure how the tester would know what the "actual" breaking load would until after the test is done. Nominal is more of an expected breaking load (i.e. 0.5" diameter, 270ksi, 7-wire PC Strand ASTM-A416, will usually break around 41.3 kips).

AMSYSCO, Inc. (

http://www.amsyscoinc.com)

 

[rapt]

Technically it should be the actual breaking load.

Maybe the Japanese are happy with nominal because their production methods are so accurate. The strand we used to get from Japan was always very close to nominal in the tests so it does not matter a lot. Some of the other strand from other sources used to vary a lot (easily 5-10%).