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Opal Tower - Sydney Australia 28

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CivilEngAus

Civil/Environmental
Jun 8, 2014
47


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.
 
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Merry Christmas!
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Sheesh. Poor blokes.

I'm VERY impressed the fire department has quickly whipped out a laser range finder to monitor the building movement.

I'm also surprised they shut off the power. Why? How does this help anyone now having to shelp up and down 34 stories. How do they get pets out down 34 stories?



Keith Cress
kcress -
 
itsmoked said:
I'm also surprised they shut off the power. Why? How does this help anyone now having to shelp up and down 34 stories. How do they get pets out down 34 stories?

Shutting off electricity and gas is pretty essential to prevent fire. Who cares about pets when there are hundreds of millions of dollars and lives and stake.


(There is every chance it will all play out fine in the short term with no harm to pets or anybody else. But the immediate concerns need to be addressed with a high degree of caution.)
 
Quotes from various media outlets below. Slightly conflicting, as I wouldn't expect the transfer to occur at level 10.

Media said:
Engineers will spend Christmas Eve alongside firefighters examining a large crack on level 10 to establish whether the building is safe and investigate the source of the cracking, Fire and Rescue Acting Inspector Greg Wright said.

Media said:
Wood & Grieve Engineers, who worked on the building, said online: “The large structural offsets at the base of the towers created a particular challenge. The difficulty was in the coordination of transferring sewer and storm water services through the deep transfer beams and large transfer slabs.”

“Due to the height of the building which imposes excessive pressures on the pipework and fittings installed on the lower half of the building, the WGE team came up with a unique dual stage pressure control concept and conducted a series of experimental tests to simulate the real working condition of the system before specifying it for installation in the building.”



 
Trenno said:
Quotes from various media outlets below. Slightly conflicting, as I wouldn't expect the transfer to occur at level 10.
I'd normally take such media reports with a grain of salt..

Plenty of plans and picture on this site:
3lPzxkI.jpg


What does seem almost certain is that several tension members, most like post tensioned strands have failed in the floor of level 10. The sounds were heard from as far as adjacent buildings. The slab has moved. Doors needed to be smashed open to get to some residents. At best it would be confined to one or two floors, but according to reports it seems to be several. Floor 10,12&13....
 
I'm not sure if it is a visual affect or if there are discontinuities in the columns due to openings in the structure for greenery.
2ULPkZB.jpg
 
So residents are being let back in. But this failure does seem to affect the serviceability of quite a few apartments and is not confined to just a few floors.

0gmI8xB.jpg
 
150 units in this building. It is reported now that about 2/3 of the residents have been allowed to return to the building. Someone, not clear who, has made an assessment that 51 units are uninhabitable for the time being. So obviously they have decided that the whole thing won't collapse, but some sort of localised distress makes a part of the building hazardous.
 
So the metaphor for the collapse of the Sydney housing market has been avoided...watch out Melbourne and Brisbane
 
Looking at the plans linked above, it appears to be grid 20 wall. Compare L9 and L10 plans, and see how that grid 20 wall is supported largely on a column below. Apartment 1005 is where it occurs.

Could wall be failing/crushing where the wall transitions/transfers to the column(s) under? Ie localised bearing failure?
 
Tomfh said:
Looking at the plans linked above, it appears to be grid 20 wall. Compare L9 and L10 plans, and see how that grid 20 wall is supported largely on a column below. Apartment 1005 is where it occurs.

Could wall be failing/crushing where the wall transitions/transfers to the column(s) under? Ie localised bearing failure?
My thoughts too. I have been hesitant to trust the structural accuracy of the architectural plan by they do seem good.

You can see the level 4 transition here:
bMQ1DO7.jpg


Open the photo to zoom in and have a look at the far left.
 
Interesting.

It seems a common transition. I wonder why it happened up higher? Stronger concrete further down?

They must be working pretty hard right now assessing it all. I wonder who gave the green light for all the other units to return? The designers?
 
The Australian newspaper has reported that the NSW government will conduct an inquiry into the problem with this building. Based on many government inquiries in Australia, this could expand to be bigger than Ben Hur. Maybe that is a good thing.
 
I think it is pretty hard to speculate at this stage whether it is a design failing or a construction failing. Based on the state of the industry these days I'd GUESS that it is a failing on the construction side of things. Naturally a design failure would likely imply similar issues at the other connections.

Regarding giving the all clear for most of the building. I suppose it was based on the fact that it has been standing for four months, what's going to change in another couple of months. (Summer heat expansion is the only thing I can think of.)

I would presume that the initial determination is just short term. Long term structural safety of the structure can't have been determined this quickly. And remediation of the damage done will be eye wateringly expensive.
 
Yeah, hard to say whether it’s design or construction issue, or both, but it wouldn’t surprise me if it’s design issue. Someone neglecting to consider that the wall needs to locally yield at the stiff point before it can engage elsewhere.

They’re taking about 1-2mm movement, so maybe that’s whats going on.
 
Have seen that 1-2 mm referred to, but not sure how you measure that when it has already occurred
 
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