Australian timber code Shear strength.

[Agent666]

Not having designed previously to this standard (based in NZ), where would I find the characteristic Shear strength for a given timber type (f's I think, don't have standard in front of me right now).

All I have been able to find via the strength group classification is the modulus of elasticity and the modulus of rupture (bending strength) within AS/NZS 287.


In particular I'm after a hardwood Vitex but good for the future to know where to find other types.

 

[nonplussed]

It's in the appendix of AS1720.1. You will need to know the stress class of the timber, usually F11 or F14 for hardwood but you might need to confirm for that species.

 

[Agent666]

OK, I'm missing how to link the strength grade, say 'S7' to what F number is equivalent it seems if that's how it's done. Maybe I'm missing the obvious then!? The strength group when looked up in as/nzs2878 only has the bending strength and the modulus of elasticity listed, no equivalent F grade?

 

[nonplussed]

Refer to table 1 in this document for the relationship between strength group and stress grade:

https://www.woodsolutions.com.au/fwpa/article_downloads/Timberspeciesandproperties.pdf

You are going down the wrong path. The timber supplier needs to tell you what stress grade the timber is or what they are able to provide. (

http://www.sitcoaustralia.com.au/vitex.php)

This manufacturer says F27 for Vitex.

Stress grade takes into account the defects in the timber, such as knots and knot spacing, splits etc. Whereas strength group is a general strength for that species and does not take into account defects. Only the manufacturer can visually inspect the timber for defects and provide the corresponding stress grade.

 

[Agent666]

Hi Nonplussed

Thanks for the info, I have the strength group from the supplier (S6 unseasoned from memory), but out of left field comes this stress grade within each strength group which I had no idea about, certainly not covered in AS/NZS 2878. I thought wrongly it was graded to match the strength group as this has a defined bending strength/modulus of elasticity (and presumably other properties).

Will ask supplier at any rate, though not sure if they will know as all they volunteered previously was the strength group which we incorrectly assumed was all we needed to look up lower characteristic strengths for bending/shear etc from relevant standards.

It seems kind of counter intuitive to have the strength group and the stress grade as there is all this overlap in F grades between each. If a bit of timber didn't make the grade on the basis of the strength group limits I would have thought it just gets bumped down a strength grade or two until it complies. That's how it works here in NZ with our pine which is the main source of timber.

Thanks.