AS3600 2017 Draft 1

[Trenno]

Just to let those who are interested know, the draft for the new concrete code has been released.

[URL unfurl="true"]https://www.concreteinstitute.com.au/News/National/AS3600-Standards-Australian-Draft-for-Public-Comme?returnUrl=/Home
[/url]

 

[li0ngalahad]

Hi
Apparently the draft is no longer available. Does anyone have a pdf copy to upload on here?

Thank you

 

[apsix]

Try this.

 

[BentEng]

Any thoughts on the new restrictions placed on the use of the simplified wall capacity method? I know plenty of buildings over 12m tall using this clause to design blade columns.

 

[rapt]

No use wondering about it now. That was a draft. if you had wondered earlier you might have been able to have some input to improving it.

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.

 

[BentEng]

Are you suggesting that this might not make it into the final code? If anything, I think that makes it even more worth wondering about, and important to discuss, regardless if the next drafting is released or not.

 

[rapt]

It has been modified in the next draft to more specifically target singly reinforced walls.

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.

 

[rscassar]

I dislike using the simplified capacity for walls reinforced with a central layer of reinforcement. I almost exclusively use 2 layers of reinforcement for any wall that forms part of lateral system. For low-rise and mid-rise buildings this is generally governed by Earthquake loads.

 

[rapt]

Agreed.

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.

 

[BentEng]

I was hoping this clause would potentially help clarify when it is/isn't appropriate to use chapter 11, however if it does only place the new limitations on singly reinforced "walls" then I guess the ambiguity will remain, and we'll continue to see blade columns designed as walls in multi-level high rises.

 

[csd72]

20 Jan 18 04:23

I dislike using the simplified capacity for walls reinforced with a central layer of reinforcement. I almost exclusively use 2 layers of reinforcement for any wall that forms part of lateral system. For low-rise and mid-rise buildings this is generally governed by Earthquake loads.

This goes back to tilt up and precast panels which are mostly singularly reinforced.

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.

 

[Agent666]

FYI in NZ they are also coming down hard on singularly reinforced walls, basically previously you could use the standard 0.85 strength reduction factor, now you need to use 0.7. You are also not allowed to use singularly reinforced walls where walls are face loaded and part of the lateral system (as there is no confined concrete). Lots of other requirements/restrictions as a result of findings from the Royal Commission into poor performance in these systems in the Christchurch earthquakes.

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.

 

[li0ngalahad]

Thanks a lot aspix for sharing the 2017 draft.
Apparently there is a new draft out for comment. Does anyone have a copy to share? Thanks in advance

 

[IDS]

See:

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/

 

[li0ngalahad]

Thanks a lot IDS

I like this draft better than the previous one, especially for the wall design chapter (previous draft limited it to 12m tall structures..)