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.

 

[QSIIN]

@SheerForceEng

We are seeing more commonly, heavy duty couplers being used to connect the precast panels vertically, and install two, sometimes three lifts of panels at a time, leaving a space for the insitu slab to be poured in between. Due to shrinkage, high strength grout is often required to fill the gap that developed between the slab and panel. Wouldn't assume that has been done on Opal, but the two options you've highlighted aren't the only methods for precast.

Using the couplers highlights other issues though, as generally not all bars are coupled (as already mentioned by RAPT and myself) meaning strain compatibility and bar development at the joint is questionable. Interaction between continuous coupled bars, precast concrete and insitu concrete is complex too, though I question how often this interaction is thoroughly checked.

Regarding the original engineers and investigation, wouldn't it be prudent that a third party engineer, with little to no vested interest, do the investigation and report, not just the original consultant...? Isn't there a conflict of interest there? Of course they are going to say "overall structurally sound"...

 

[Tomfh]

Human909, they are propping heavily below L4, which would suggest they are concerned with the slab as well and not just the connections to the panels supported by L4.

 

[degenn]

The “transfer” you are talking about looks to be only a 200 slab, like all the rest. The floor to floor height looks consistent. With 20 floors above, you can’t expect any reasonable redistribution without punching the slab.

The problem with propping to ground is how the get a say 10000kN foundation for the props.

 

[human909]

Propping is occurring from the basement upwards and and probably is aimed to extend at least to level 16. It would be to reduce the load on the existing compression members so that no further damage is done and to allow remediation once they figure exactly why and how. Remediation becomes a whole lot more difficult once the slabs has moved!

Regarding the original engineers and investigation, wouldn't it be prudent that a third party engineer, with little to no vested interest, do the investigation and report, not just the original consultant...? Isn't there a conflict of interest there? Of course they are going to say "overall structurally sound"...

The main investigation and remediation is being carried out by the responsible company, WSP. I would suggest that they are being very thorough now, they are engaging other engineers from within the firm as well as engaging engineers (presumably specialist) from another private company.

On top of this the state government has formed a engineering investigation that is participating in all this. (This isn't a normal action, but given the severity and the high profile the government has jumped on this.)

I would say from an engineering standpoint things are going to be pretty thorough from now on.


I can't explain why the early decisions and statements were made about the building's structural soundness. But it does seem like they were driven by the vested interests of the developer "Ecove" and builder "Icon". These are the ones with their necks mostly on the line in terms of immediate costs and reputation. WSP obviously will face issues if there is a structural design flaws.

 

[CivilEngAus]

https://www.dailymail.co.uk/news/ar...pal-Tower-debacle-begin-fiery-blame-game.html

I'm not sure how reliable The Daily Mail is although they have a new photo from apparently inside an apartment.

Apartments have already been - or will be - gutted on levels four, six, seven and 10. ...

This will include, but is not limited to, removing the walls to assess the structural damage.

New images show the interior of one such apartment that has already been assessed, showing a temporary metal wall in lieu of the plaster and exposed wires hanging from the roof.

The cost of the metal props currently holding the building up is said to be in the hundreds of thousands, and more are currently on their way from international sources to due a shortage of supply locally.

The ground level of the building has also been jackhammered and pavement ripped up.

Engineers are allegedly calling for the further inspections to garner a more holistic understanding of the causes and impacts of the current debacle.

They are also arguing it will allow them to assess the extent of the damage, amid rumours the engineers involved are currently at a loss as to how to go about repairing the building.

The new details come just days after allegations surfaced that two new cracks on level four had been found.

 

[Tomfh]

Just a bit of bad grouting hmm...

 

[rscassar]

If it is the grout beds of the precast walls and it went unchecked through construction, the cracking of these walls could be extensive throughout the whole building. When they take off the finishings for all the walls & columns up the tower there could be more surprises yet. I don't think this building will be re-opening anytime soon, and I'm not sure there is a successful remediation for this building.

This is going to send shockwaves throughout the whole highrise building industry in Australia.

 

[human909]

Whatever the reason for vertical displacement, even if it is just 'bad grouting', the consequences can be severe. This part we have known pretty much from the start. When you have slabs on multiple levels moving enough to jam doors rectification is always going to be challenging. Appartments gutted and ground jackhammered is likely just inspections and installation of props. If you have a tiled ground floor you are going to want to remove them before placing the props. (Which must extend down the the basement foundations.

That said, that picture above looks like they are possibly still concerned about the strength of the precast panels. (despite comments their comments to the contrary) But I feel like I'm doing too much guessing now, I've done enough already!


One thing to observe. If anything the media coverage of this is getting worse. Reporting rumors as fact which have forced denials.
EG on the previous level 4 cracking:
Design firm WSP — one of the investigators being employed by the building company Icon — denied reports the cracks on the fourth floor had widened from 3mm to 20mm over the past week, with chief executive Guy Templeton declaring them “completely not true”.

“We’ve gone through the rest of the building, that (cracking) has been there for an indeterminate amount of time, not necessarily the same,” he told The Australian. “It’s been monitored and it hasn’t moved at all. It’s just a bit of cracked concrete, not very exciting.”

 

[rscassar]

I'm actually surprised that they are speaking with the media openly as they are. Given what is at stake, I would expect any interviews with the media they would be very polished and deflect questions without given a definitive answer. Like a politician does when they get grilled by a journo.

 

[rapt]

Human909,

You have had an awful lot to say about this considering your own admission to having very little experience in this area and no knowledge of what has actually happened with the building.

Some comments like

"The main investigation and remediation is being carried out by the responsible company, WSP. I would suggest that they are being very thorough now"


could be regarded as slanderous. I would be confining myself to known facts, very few if any of which have been aired by anyone on this site.

RE WSP, they merged with Winward Structures several years ago when WSP moved into Australia. Winward were previously part of Bonacci Winward but they split in the early 2000's to form Bonacci Group and Winward Structures. There is no other connection between the 2 groups that I know of.

 

[Sheer Force Engineer]

We are seeing more commonly, heavy duty couplers being used to connect the precast panels vertically, and install two, sometimes three lifts of panels at a time, leaving a space for the insitu slab to be poured in between. Due to shrinkage, high strength grout is often required to fill the gap that developed between the slab and panel. Wouldn't assume that has been done on Opal, but the two options you've highlighted aren't the only methods for precast.

Hi QSIIN, you are spot on, however the two methods I have outlined remain the only standard approaches for the base where a wall/column starts at footing level (or in this case where a discontinuity or transition occurs and the wall/column doesn't continue to levels below in the same configuration.

For the "block-out" method, you are still left with the conundrum of how to grout the gap that is left between underside of column surface and top side of slab (you have one of two options which I have outlined above).

Regarding the original engineers and investigation, wouldn't it be prudent that a third party engineer, with little to no vested interest, do the investigation and report, not just the original consultant...? Isn't there a conflict of interest there? Of course they are going to say "overall structurally sound"...

There is definitely a conflict of interest however this is generally the first port of call in a situation such as this for a few reasons:

- The original engineer already has significant analysis and understanding of the building (hopefully!!) and at short notice in critical situations can hopefully give some fast answers after re-checking or internally peer reviewing the design to either confirm or disprove that design is an issue.

- To get another engineer at short notice means approaching the firm, getting the scope agreed, getting the fee sorted, then the contract. With occupants inside, this is not ideal.

- Some firms steer clear from getting involved in these kind of situations altogether for fear of having their name associated with the debacle.

When the situation escalates and a logical answer is not found (or the prevailing answer is one that the developer/builder etc. is not satisfied with) a third party is then involved which now looks like is happening...

It looks like Rincovitch and Cardno are also involved now so there are plenty of eyes looking at the situation (with no vested interests, albeit one vested interest to one-up a competitor and get some PR out of the process which when scrutinising a design in this case would be a good thing as it gives added motivation to do a thorough peer review!!)

As a side comment, I've never seen so much significant propping in a "structurally sound" building before which is exhibiting cracks that are "not very exciting"

 

[human909]

Human909,
You have had an awful lot to say about this considering your own admission to having very little experience in this area and no knowledge of what has actually happened with the building.
Some comments like
"The main investigation and remediation is being carried out by the responsible company, WSP. I would suggest that they are being very thorough now"
could be regarded as slanderous. I would be confining myself to known facts, very few if any of which have been aired by anyone on this site.

That emphasis is yours not mine. Slanderous, well that is your opinion. I believe I have stuck to the known facts and where conjecture has taken place I believe that has been clear. I don't believe I have misrepresented unknowns as facts. This discussion, and certainly my comments, are meant for the interested parties in this forum. If we wanted to wait until all the facts were public before discussing the topic then the topic would never get discussed.

If you consider my contribution as useless, then that is your opinion. Personally I have valued the contributions of everyone here, even those who I have questioned or who have questioned me.

**Failure/accident analysis is a fantastic way of learning and a great way of not repeating past mistakes. Open discussion is a great way to engage the mind on the topic. Honestly I wish it was promoted more heavily in all aspects of engineering.

 

[mangotree]

Wow, sounds like a structural engineering soap opera!

Thanks rscassar for your reply on the 31st Dec 2018. I appreciate that.

I learnt a lot from your comments too, SheerForceEng. Your explanations are very clear and thorough, and it’s great to have someone with your experience sharing your thoughts.

I happened to come across an article from the Financial Review, titled “Opal Tower: Ecove developer Bassam Aflak says builder Icon bears liability” by Michael Bleby dated 1st Jan 2019.
If you google search the title, you can read it online. Here’s an excerpt:-

Start of Quote
“Tensions rise to surface
As technical experts scramble to understand the cause to cracking in the building that has dominated national news headlines over the past week, tensions are bubbling to the surface between the main players. Mr Aflak said his own project managers were party to the structural investigations taking place but he was not aware consultancy WSP was putting out a statement late on Monday saying other cracks had been found but that the building was structurally sound.
"You would have seen a release by WSP Australia last night, which we only found out about this morning as well," Mr Aflak said. "There appear to be two locations where they're identified a crack. We're still waiting for a full report."
The problems had occurred in "garden slots" – recesses in the facade on the fourth, 12th, 16th and 26th levels of the building – where precast concrete panels joined structural columns and engineers needed access to about 40 apartments to inspect those connections, Mr Doyle said.
"What caused it will play out over a long period – whether it's precast related or related to the column connections."
He said one potential cause, the grouting sealing the connection between panel and column, was not a problem.
"The type of grouting didn't raise any concerns," he said.
Both Mr Doyle and Mr Aflak said the building was safe for occupation. Mr Aflak said he hoped the majority of residents – apart from those living in units that still required invasive testing to determine problems – would be able to return home sooner than the 10 days Icon said was necessary, when it evacuated all the residents for a second time last week.
"I'm hoping once we have a plan and a resolution this week from the engineers, everyone will be in a position to put a plan of action in place – I think the majority will end up coming back earlier than anticipated – and working out a plan of action for the balance of them."
Mr Doyle, who said the timeline of any remediation work – and consequently, any return by residents – was subject to approvals given by the government-appointed engineers, was non-committal.
"I can't answer that," he said. "It's out of our hands at the moment." “
End of Quote

I’m not certain whether the grout in the article refers to the same under panel grout discussed here.

 

[Tomfh]

Human909,

Yes, we should all discuss failures more openly. The way everyone hides mistakes is really sad.

I often wish for The Big HandBook of Structural Screw-ups so we could all learn where the most common pitfalls lie. Too bad it doesn’t exist because everyone invariably clams up. It’s only ones like Opal which make the news which get out there for all to see.

 

[human909]

Yes, we should all discuss failures more openly. The way everyone hides mistakes is really sad.

I often wish for The Big HandBook of Structural Screw-ups so we could all learn where the most common pitfalls lie. Too bad it doesn’t exist because everyone invariably clams up. It’s only ones like Opal which make the news which get out there for all to see.

Exactly. And although rapt may have a point about unnecessary speculation and analysis, there is also the counter point of not enough analysis or review.

There have been numerous times in my professional career that I have questioned things around me in the absence of all the facts. If you wait until you have all the facts you might be waiting forever. Sometimes I've had to eat humble pie after questioning things because I've been wrong. Other times I've caught errors before they have led to more serious issues.

There sorta is a "HandBook of BIG Structural Screw-ups", (note the rephrasing). But it readily misses all the small screw-ups which can include equally important lessons. One of my hobbies is a risky activity that involves plenty of risk assessment with analysis that engineers are often more adept with. Knowing and understanding past mistakes can keep you and others alive. Open discussion is important for the community to understand the risks and pitfalls.


EDIT:

In other news. This article (despite being from a tabloid media source) is one of the best summaries I've seeen regarding the chain of the responsibility for the construction.

https://www.news.com.au/finance/bus...r/news-story/02d13f5cac8b41fe9b600c111118d346

 

[Agent666]

Meanwhile, AAP has reported that structural engineers investigating the building’s cracks believe a prefabricated concrete panel was not inherently faulty.

Instead, they think the damage was potentially caused by how it was installed, or possibly by problems in the design or construction of the building itself.

From this news article, Link. If true seems to narrow down (or widen) the field of possibilities.

 

[Agent666]

To throw something else into the mix, it's possible that whatever grouted connection is present between the insitu and precast was not grouted at all. This would seem consistent with the events/damage I'm extracting from the limited information that's avaliable.

Hokie66, I'm very surprised that engineers inspections are being neglected. Engineers are one of the important links in understand what is going on sometimes and understand the impact of changes, etc. They are the policemen of the construction world, putting you head in the sand thinking you are limiting your liability by not inspecting is potentially completely the opposite of the situation if something goes wrong (liability through professional neglect). You have an obligation to prevent problems that might lead to the design intent not being achieved in my view, and am obligation to protect the public. Shame Australia doesn't seem to have learnt from the NZ experience in the 90'swith regard to the leaky buildings fiasco (and we didn't learn from exactly the same Canadian experiences a decade or so earlier as I understand it).


Wondering in Australia are the drawings/calculations/specifications part of the public building record like in NZ, so anyone can simply request the building records from the local council? I'm guessing not, as my recollection of doing work in Australia 15 years ago was that I never even had to submit calculations or anything like that.

 

[IRstuff]

Can anyone confirm that the column configuration was definitely changed between the issuance of the architectural drawings and the actual construction?

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[rapt]

Human909,

The emphasis was added to show where I thought the problem was! You wrote it!

To suggest that they are being thorough NOW is to suggest that they were not previously, and that is still not known. In fact, were WSP the original structural consultants? Bonacci are listed as the structural consultants in the listing of consultants for the project. WSP are not mentioned, and are not related to Bonacci in any way.

In that comment above I was not referring to speculation about the cause of the problem, though I still find it amazing that there has been so much discussion without the existence of any factual information. As far as I know, no-one has seen a structural drawing or calculations, or even a final architectural drawing or even knows what the connection looks like.

 

[Tomfh]

Rapt, now that things have gone bad, WSP are obviously taking a much closer and more thorough look at the panels/grouting etc than they did previously.

So there’s nothing wrong with them saying they’re being much more thorough with it NOW that it’s failed. That’s what happens when things go bad.

You don’t do a forensic check of every square inch of grouting and concrete in normal practice. You don’t order apartments to be gutted so you can check the concrete.