AS3600 2017 Draft
AS3600 2017 Draft
(OP)
Just to let those who are interested know, the draft for the new concrete code has been released.
https://www.concreteinstitute.com.au/News/National/AS3600-Standards-Australian-Draft-for-Public-Comme?returnUrl=/Home
https://www.concreteinstitute.com.au/News/National/AS3600-Standards-Australian-Draft-for-Public-Comme?returnUrl=/Home





RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
It would seem our designs just got 5% better, given most of the reduction factors have increased by 5% (for example shear phi = 0.75 instead of 0.7).
RE: AS3600 2017 Draft
No, the materials got 5% more reliable than they were 40 years ago apparently!
RE: AS3600 2017 Draft
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
Where does it say that?
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
I meant in the Draft! 8.2.4.2 will allow theta up to 50 degrees based on a strain of .003. And it does allow the designer to use a value > than the calculated equilibrium value but no greater than 50 degrees. As you suggest, the model is based on the Canadian MCFT and the theta chosen is more logical than the old method. RAPT has been using the minimum value depending on level of shear compared to Min and Max for many years, so normally significantly less than 45 degrees and often as low as 30 degrees.
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
The last paragraph of 8.2.4.3
"kv and thetav may be determined from Clause 8.2.4.2 using a value of εx that is greater than that
calculated from the equation in this clause. The mid-depth strain parameter εx shall not be
greater than 3.0 * 10-3."
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
It is not technically a limit on theta, it is a limit on ex, which is used to calculate theta and then kv
RE: AS3600 2017 Draft
Does anyone know the intent of <Table2.2.2> (j) "Bending, shear and axial force in singly reinforced walls forming part of a primary lateral load resisting system" resulting in theta=0.65.
I interpret the "primary" to mean walls subject to in-plane shear/structural wall action and NOT out-of-plane actions (i.e. face loading of slender walls)
Cheers
Toby
RE: AS3600 2017 Draft
I think "primary lateral load resisting system" might give it away!
RE: AS3600 2017 Draft
True, pure semantics - but in my book out-of-plane resistance is of primary concern in resisting lateral loads.
I assume the reduction for singly reinforced walls relates to the lack of confinement in the "boundary elements".
What of seismic 100% in-plane loads coupled with 30% out-of-plane and vice-versa, which would seem reasonable in that out-of-plane action of walls must contribute to action perpendicular to them, which they may have demand placed upon them from buildings torsional response. Also "primary lateral load resisting" elements located at a building corner will receive in-plane demand and out-of-plane demand form wind loads.
So my take on this would be to reduce in-plane response mechanisms by theta=0.65 (when acting alone)
and to reduce out-of-plane response mechanisms by theta=0.8 (Class N reo) - out-of-plane buckling a consideration for effective struts from in-plane action coupled with direct out-of-plane actions.
Example
A typical rectangular tilt building with large opening in wall on "short" side.
The wall "pier" will be subject to in-plane demand from actions parallel to "short" direction of building and out-of-plane actions from "header" over in a tributary sense....
Got called away - may give it more thought and get back later
Cheers
Toby
RE: AS3600 2017 Draft
What I was getting at essentially was that are we to "blanket" all singly reinforced walls with theta=0.65, or only when the bending, shear and axial forces are considered as "in-plane" actions.
Back to tilt up buildings - it would seem unreasonable for a wall subject to out-of-plane bending, with N-class reinforcement that meets the minimum ratios and demands to be assigned theta =0.65. Essentially a wall designed utilizing the findings of the slender wall task committee and SEAOC bluebook recommendations should be sufficiently reliable with theta =0.8-0.9.
Maybe too many tilt panels have been designed ignoring minimum steel quantities, with L class reinforcement and neglect of P-Delta effects, that theta=0.65 is warranted. In my opinion such poorly designed walls would need more than theta=0.65 to make them sufficiently reliable.
Toby
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
If this blanket theta applies to out-of-plane actions then 2 identical walls in every way, except one has L class and the other N class, would be "rated" the same.
RE: AS3600 2017 Draft
Apparently the draft is no longer available. Does anyone have a pdf copy to upload on here?
Thank you
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
Now you will have to wait until the next version of the draft is released to begin wondering again.
If you are registered as an AS3600 owner/user with standards they will probably tell you when it is available.
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
But the next draft is already written, so it is too late to change except by comment on the draft when it is released for comment in the next couple of months.
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
I also do not think the simplified wall method was ever meant to be used for blade columns. That was part of the reason the "wall definition" of length > 4 width was removed from the code many years ago. Unfortunately is was reintroduced in the fire design section and now many consider it to apply to design of columns/walls in all situations.
It was introduced for fire as a longer column will have less heating of bars as the corner bars, which are affected more by heat, are less dominant.
RE: AS3600 2017 Draft
RE: AS3600 2017 Draft
There has been testing over the years to prove that they are more robust than you may think.
Not all buildings are affected by the earthquake provisions.
RE: AS3600 2017 Draft
Part of the reason is that concrete is much stronger over time than the design value, so rather than forming distributed cracking to dissipate energy you get a single crack (with lower reinforcement ratios at least) and hence reinforced capacity can actually be lower than the uncracked concrete capacity. This generally results in bar fracture due to low cycle fatigue after a low number of cycles, as might occur in a seismic event.
As I believe it the intent of the recently updated NZ provisions are essentially making sure that the walls behave almost in an elastic manner up to the Maximum Credible Earthquake (MCE, 2500 yr return period event).
There might be laboratory testing to show they are robust, but real events in NZ recently generally showed in certain circumstances very poor performance.
RE: AS3600 2017 Draft
Apparently there is a new draft out for comment. Does anyone have a copy to share? Thanks in advance
RE: AS3600 2017 Draft
http://www.eng-tips.com/viewthread.cfm?qid=436319
My link in the fourth post should give a free pdf download for anyone in Australia.
Apparently it's not free for those outside Australia.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/