Reporting Split Tensile Strength in SI units

[BigH]

Just want to see how you all would handle the following reporting instruction as given in ASTC C 496-96.
"Splitting tensile strength calculated to the nearest 5 psi (35 kPa)"

Say my splitting tensile strength is calculated to be 1133 kPa. How does one report this to the nearest 35 kPa.
Is it:
(1) 1135?, or
(2) 1133/35 = 32.37 round to 32, then 32*35 = 1120, or
(3) 1133/6.894757 psi/kPa = 164.32 psi round to 165 (nearest 5 psi) then 165*6.894757 = 1137 kPa.

They did the same thing when going to SI with compressive strength - round to nearest 79 kPa - then they finally changed it to 0.1 MPa.

One interesting point is in the paragraph on Precision and Bias - they gave numbers of 405 psi (2.8 MPa) and 400 psi (2.8 MPa). Note that they didn't even use kPa as required under reporting. Mmmmmmm

 

[iandig]

My initial view would be 'option 2' as this relates to the principal that 5 psi is = to 35 kPa. Therefore my understanding of the intention of the specification is to report to the nearest 5 psi with this being taken as a reasonable level of accuracey for the test.
If it was me, and I was using this standard, I would look at calculating the results using both kPa and psi and assessing the difference between the results. Plus, being a bit of a nerd with spreadsheets, I would plot the result on a graph with the tensile strength in 35kPa incriments, then select the 'reported' value by inspection.
Knowing how confusing this will be, you will end up with 7 different results, which can then be used for an upper bound, lower bound and characteristic value.

 

[woofar]

I think you should seek clarification from your accreditation authority. The clause is obviously flawed as 5 psi = 34.4737864 KPa. To my mind, such an obvious ambiguity is an unforgivable error for a national standard. Personally, I would not sign off on a report to that standard unless I had a clarification in writing.

 

[BigH]

34.4737864 doesn't equal 35 ? Really?? (as far as practicality goes for test results, it does). I'd have no problems signing off . . .
If you question this, question the conversion of steel rebars from Grade 40, Grade 60 to Grade 300 and Grade 420.
The question doesn't pertain as to whether 34.47+ = 35 but how does one actually round off to the nearest 35 kPa given a particular result - such as 1324 kPa??

 

[henri2]

Big H,

Interesting post.

I agree with iandig. Your option 2 in the OP seems the way to go. It keeps things simple. So using your option 2, I'd report 1324 kPa as 1330 kPa (1324/35 = 37.83 round to 38, the 38*35 = 1330 kPa).

With all other uncertainties regarding material strengths and loadings, which are handled by relevant factors of safety, strength reduction factors etc, the conversion errors appear minor and thus acceptable, no?

 

[BigH]

Good to see you back Henri!

I posted the question sort of tongue in cheek as it seemed inane and ludicrous that ASTM would have actually made the "SI" change without reviewing its practicality - but they did (and earlier on compressive strength). I ended up telling my lab guy to "cheat" a bit and we have reported it to the nearest 25 kPa. Easier to do and it divides evenly into 100.