AS 4600: Capacity reduction factors for bolted connections - Lapped sheets in tension

[human909]

It would seem that AS4600 has some pretty onerous limitiations when bolting steel sheet together. I'm considering two lapped plys of steel bolted together and the loss of capacity you get compared to say the EU code is significant.

4600 CAPACITY REDUCTION FACTORS
"Net section tension: 5.3.3
With washers— 5.3.3(a)

double shear connection 0.65​

single shear connection 0.55​

Without washers 5.3.3(b) 0.65"

0.55 is a pretty significant capacity reduction on what is largely a simple connection. I'm not sure why the difference with washers but I'm sure somebody might be able to point me in the right direction.

In contrast:
EU.1993.1.3.2006 Pages 62-67
Have largely the same capacity calculation but have a reduction of 0.8!

So for the same design 0.55/0.8 you have a 69% loss of design capacity when following AS4600 compared to the EU code.

Is there anything I'm missing? Or is it just a difference in codes? [EDIT it seems the US codes have the identical reduction factor to AU, so EU seems signifacantly less conservative.)


As a deeper background I'm hoping to approve an EU designed structure for AU conditions. When you have 30% loss of capacity between the codes it can get kinda tricky!

(This research paper gets deeper into the nitty gritty of the various codes on these connections. However it doesn't get into the capacity reduction factors.

https://ro.uow.edu.au/cgi/viewconte...&httpsredir=1&article=7339&context=engpapers)

 

[human909]

It seems I'm busy answering my own questions:
Digging up this:

https://ro.uow.edu.au/cgi/viewcontent.cgi?httpsredir=1&article=2176&context=eispapers

Shows I'm not the only one who has come to the same conclusion base on empirical research.

"It is proposed that a resistance factor of 0.80 be applied to the new equation to ensure a reliability index of not less than 3.5 in the LRFD approach of the North American specification for the design of cold-formed steel structures."

A selective quote but read the whole article if you want to know how they got that figure.


Not to mention the that washers both sides do seem to result in strength increase DESPITE what the code implies.

https://steel.org/~/media/Files/SMDI/Construction/CFSD - Report - RP08-11.pdf

 

[Agent666]

I don't think you are looking at the latest 2018 version of AS4600. There were some changes in this area based on looking through the latest version (that may or may not address your ambiguity?).

 

[human909]

Thanks Agent666!

You are absolutely correct. Damn glad those changes have been made. Suddenly the structure 45% stronger.