Opal Tower - Sydney Australia 28

[CivilEngAus]

https://www.news.com.au/national/ns...s/news-story/dad28af4aad5ff11cf968102635824f9

https://www.smh.com.au/national/nsw...ns-building-may-collapse-20181224-p50o4b.html

This could be an interesting and developing story in Sydney Australia. A 34 storey near new residential apartment tower in Sydney has been evacuated this afternoon over fears it is in structural distress with cracking noises heard during the day and one or more cracks developing; emergency services are treating it as a major incident.

Given we already have some of the toughest building codes in the world (although little to no registration requirements for engineers) it will be interesting to see how this plays out and what the crack(s) looks like to cause such a major emergency response.

 

[mangotree]

Yes, you're right MDEAus. That photo is in the interim report.
Thanks for that.

 

[Agent666]

Statement from WSP regarding the repairs and reoccupancy. Link

This suggests they are concentrating only on strengthening/repairing 3 wall locations on each of levels 4, 10 & 16.

 

[david256]

60 minutes on Sunday shows some of the repair work.

https://twitter.com/60Mins/status/1090897475940962304?s=20

 

[Agent666]

Interesting, that looks like a simple surface patch to replace the spalling concrete. Wonder how they strengthened it, and/or addressed the underlying design issues.

I was in all honesty imagining something completely different would be required if they were addressing what I'd see as the obvious issue/deficiency in the original detailing based on the observed damage. An apparent surface patch hardly addresses the apparent lack of confinement. Obviously no one has officially said what they think the apparent design errors were, so hard to say if this type of repair would address the underlying design and construction issues.

 

[david256]

Agent666, yes it's definitely confusing especially considering the level of damage we've seen in photo's and videos.

 

[Tomfh]

If they’re building a new wall to bypass the hob junction wouldn’t they not bother strenghthening the cracked hob?

 

[mangotree]

Have they used some kind of structural epoxy adhesive injected into the cracks?

I wonder what they found about the reo in all the other panels. Apparently there’s a “concrete scanning” service that uses ground penetrating radar (GPR) technology to locate reinforcement. Not sure whether the equipment can size them or not.

 

[david256]

mango tree, it definitely looks like an epoxy it would be interesting to know if they are using it to strengthen or repair the panels. And it'd good to know what they're doing on the other side of the panelled wall. Hopefully we'll see more on Sunday night.

Took some screen captures of the 60 minute video, you can see the other side of the hob beam and you can see they have repaired a slab crack with something again looks like an epoxy.

https://imgur.com/a/vgcAnsV

 

[hokie66]

Injecting all those cracks is not getting to the root cause of the distress. If the problem is with inadequate reinforcement, they are just pushing water uphill. Will be interesting to see further reports.

 

[david256]

Yeah, it looks like they're just repairing the cracks, I was expecting some kind of permanent column supports would be installed on the inside of the panel wall, taking some load off the wall and hob beam.

 

[Agent666]

These superficial repairs could just be part of the preliminary stabilising works vs being part of the final remedial to address any shortfalls in design or construction. Though its finished off so nicely at the base that it seems like that's it for the outside at the bottom apart from reinstating the waterproofing.

I would have thought that their would have been some further comments by the university professors by now if they are getting into the repairs, as the public still has no idea what the design issues are, that they are being effectively handled, etc. Yet a considerable portion of the tower has been opened up for reoccupancy based on WSP/Icon/Cardno agreement.


For those of us outside Australia, please post back on the 60 minutes programme content. Any idea if they stream it?

 

[Tomfh]

I thought they are casting a new wall inside to bypass the defective hob/grout junction?

 

[rapt]

Agent666,

I know we live in the information age (much of it mis-information) but I cannot understand why you would think they will give a running commentary on the whole project!

 

[degenn]

I can totally understand why the developer, builder and engineer wants to keep it quiet but do they have an obligation to explain more when there is such public interest and the entire industry is being brought into disrepute

 

[Agent666]

Hi Rapt
That's not exactly what I meant but I can see it was a bad choice of words on my part. I thought their mandate was to produce a public report on cause and comment on proposed repairs (items 1 & 2 of their scope). These repairs seem to be underway of course, and one recommendation was that the design of any repairs was peer reviewed by independent and qualified engineers, which I assume and hope someone is at least doing.

I have not seen anything at all about this, but if I were a PR guy for the designer or contractor I'd be outlining to the residents that someone is at least doing this to alleviate their concerns. Otherwise its the guys who made the mistake fixing the mistake, and well that doesn't fill me with a whole lot of warm fuzzies to be honest based on my own experiences.

The professors issued an interim report, but it basically said nothing technical apart from raising more questions to a curious engineer reading it with a view to finding out what the root causes were.

As others have said, the explanation that seems to come out of the interim report is the suggestion that people moving in caused the overload resulting the damage and failures observed. I find it interesting that something that clearly had capacity issues, with possibly less than normal serviceability loads can have some propping added and the people involved are saying its all structurally sound and no worries so people can move back in while repairs are being undertaken (maybe they are advising they don't take their furniture back, just in case!...).

I have a hard time believing that there are not more design issues throughout the structure than the areas that failed, but I'm a cynic. Too many years of doing peer reviews to know where there's one mistake, that there are generally more if you go looking.

I honestly have no idea what if any involvement the professors still have, but what I really meant was I would have thought they still owe a final report at some point that actually fully addresses the scope they were asked to report on, being:-

1. - determine the basis of the failure, what happened and how?
2. - The immediate steps that need to occur to ensure the safety of the building for its occupants

I find it interesting on a personal level as this type of thing simply isn't supposed to happen in a country like Australia given all the checks and balances and modern codes and building practices that are in place. Like degenn notes, it reflects poorly on the industry as a whole and the media/politicians at least have certainly tried to turned it into a witch hunt on the whole construction industry in AU.

I am almost certain if this was a structure I was peer reviewing that the apparent lack of confinement (which I see as being a prime contributing factor to the damage we are aware of) would have been raised as a red flag and we would have insisted on something being done about it. However in Australia as I understand it you don't have the same level (or any) independent design review like NZ does. So when a designer potentially gets it wrong, it is wrong, there is no safety net, and every now and then it goes wrong when all the holes in the Swiss cheese align.

 

[rapt]

The logic that people moving in caused the problem is absolute rubbish.

Total dead load would be about 7 or 8kPa while full design live load is 1.5kPa. So live load is relatively insignificant compared to the building load before anyone moved in. And construction loads would have been similar or higher. Wall design loads from Wind and earthquake would have been higher than LL!

Like everyone else I would like to know what is happening and think there are major construction problems as a minimum. But I am not expecting any information in the near term.

Anything on 60 minutes will normally be sensationalist mis-information in my view so I will not be watching it. Making it worse will that the Tomic love-in will be on the same show!

 

[mangotree]

I am also wondering when the professors’ final report will be issued, especially since people have already started re-occupying the premises.
It would give them a certain level of comfort if an independent public authority confirms the process.

This is after all, a defective structure built on public land.

If they don’t release any formal documents, all that would be circulating in the public domain would be the tabloid-oriented news, but at least the public gets some insight into the rectification.

Tomfh – I haven’t heard anything about a new wall. Are there any more details?

 

[david256]

Current Affair is running a special this week, supposedly construction videos, it'll be sensationalised but the images will be interesting.

 

[Tomfh]

The ACA preview footage looked interesting. Spalling columns and lots of slab soffit cracks.

 

[tornear]

Columns shown in the ACA preview look like the result of concrete getting behind the plastic liner inside a formatube (or similar form system).