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.

 

[rapt]

rscassar

That last picture would appear to show a near vertical crack in the wall. Not a compression crushing failure. The base of the wall at the floor appears to be intact as does the "grout" bed.

RE the review, there would appear to be several consultants involved as well as the Government appointed Deans from UNSW and Uni of Newcastle. From what I understand, WSP, Cardno and Rinkovitch are representing different groups as well as Kajima's own people.

 

[epoxybot]

I pieced this photo together from the NZ Stuff video. There is more going on than Agent 666's screen grab shows.

 

[rapt]

Keeps changing.

So it is not a wall according to that photo, it is an upturned beam! And it looks like a flexure-shear crack/failure. And it is right through the depth. You can see another much finer crack at the top right hand corner.

 

[Tomfh]

I thought it was some sort of fold in the slab, so that garden is below the units.

 

[human909]

To me that seems like the window, the wall and the slab shown in this image (LEVEL 10, APT1005). The covering (?tiles?) and the planter box have been removed. The focus of the image is the top of the SQUARE column previously mentioned and the precast panel. My thoughts anyway. But it could be in a completely different area given we have no context.

Link

EDIT1: It also readily explains the 45degree cracking from what could be a steel shim between the wall and the column. This goes back to what rscassar conjectured earlier. The wall is offset on the square column, which is unideal but given the desire for clean architectural lines in the gardens it is understandable.

EDIT2: Added a picture to make it clearer what I'm suggesting. (Thicknesses of slab/wall and dimensions of column relying completely on rscassar's previous post.)
Link

EDIT3. I've gutted this post as I misconstrued the context of the photo. I believe ShearForce's post below is more accurate.

 

[human909]

Meanwhile the insight into the political and legal quagmire continues:

'Design and construction issues': residents claim investigators not cooperating
“WSP and Icon are not cooperative with [the] engineer appointed by [the] body corporate,” the residents claim in the letter.
Chief among the residents’ concerns is their claim that WSP and Icon have denied Mr McMillan access to “equipment and drawings to facilitate his works”.

The headline and claim is a little bit inflammatory. The investigators (WSP) likely have no requirement to cooperate, and might be contractually obliged not to disclose such information. But it just exposes how powerless the actual OWNERS of the property are. As the owner (joint owners) of the property you would hope that access to structural drawings of your own property would be your right. As it turns out it isn't quite that easy.

No doubt none of these issues are new in the industry. They simply have been brought out into the spotlight by this drama. And this is all in the context of a brand new construction. Imagine the nightmare for the owners if the building was outside the 'warranty', which I believe is only 7 years.

 

[Settingsun]

Has there been an explanation of why the developer, builder & designer are in charge currently, rather than the owner's corporation? Is it by default or is there some law/contract that makes it so?

 

[CivilEngAus]

A couple of screenshots taken from a Seven News video from two days ago.

No context on the location.

The image has been taken with a drone.

RE the review, there would appear to be several consultants involved as well as the Government appointed Deans from UNSW and Uni of Newcastle. From what I understand, WSP, Cardno and Rinkovitch are representing different groups as well as Kajima's own people.

Who are Rinkovitch working for?

https://www.instagram.com/p/BaKu-MqH7S8/

The Opal Tower Project at Sydney Olympic Park celebrated the #toppingoffceremony amoungst team member & clients. This milestone was achieved 19 weeks ahead of contract programme and the 36 levels above ground were completed at less than 6 days per level. Congratulations to the Opal Tower project team!

October 2017

I don't work in high rise although 19 weeks ahead of schedule sounds mighty impressive...

 

[human909]

Has there been an explanation of why the developer, builder & designer are in charge currently, rather than the owner's corporation? Is it by default or is there some law/contract that makes it so?

Not there hasn't. But it can largely be surmised. (I am not a lawyer, nor do I know the contracts involved.) But in summary there is nothing that gives the owners or the owners corporation the power to 'be in charge'.

The Developer (Ecove) is the contractually obliged to the owners. There are statutory warranties regarding structural defects between the Developer Builders and the owners. The Builder (Icon) is contractually obliged to the Developers and they are the ones currently covering costs of investigation and relocation of residents. WSP presumably have contractual obligations to Icon and are also (as the original engineers) in the best position to assess the issue.

Icon has put itself in charge as it knows it it liable. Most of those involved have just played along willingly so far. (Though some owners initially and maybe still are, refusing to cooperate with offers and requests from the Icon.

 

[rapt]

My understanding is

WSP - Ecove
Rinkovitch and Kajima - Icon (majority owned by Kajima)
Cardno - Owners/Body Corporate

This could be wrong as it is gleaned from press reports!!

 

[Tomfh]

Human909, you just own the space between the structure. The joys of high rise strata living.

 

[mangotree]

I don't work in high rise although 19 weeks ahead of schedule sounds mighty impressive...

You might be on to something CivilEngAus.

It would be good if the construction programme was checked against when the concrete slab would be cured/ robust enough before it’s subjected to various loads eg. Load bearing panels, post tensioning, and also checked against weather conditions.

I’ve read someone’s comment that sometimes the recently poured slabs appeared diluted down with rain (a general comment NOT specific to the Opal Tower). Would that affect the structural engineering calculations? Or would there be no long term implications?

The problem is, the residents are talking about a class action lawsuit.
That’s the likely reason for the lack of co-operation with the external professional engineering investigators.

 

[degenn]

Am i correct in reading the latest photo as a vertical crack in the wall over the centre of the column? If so, it would appear that a tensile force existed in the base of the wall due to the rectification of the dispersed column force into the wider wall. This force would be say 10% of the axial compression and enough to crack the wall. It appears to have cracked the slab also. If the wall had only minimal horizontal reinforcement the yield would occur until to crack was long enough to have enough bars to contain the crack growth.

This L10 panel should have additional horizontal reinforcement. The panels above need not. The panels would otherwise be the same. Any chance of a mixup?

 

[Sheer Force Engineer]

I pieced this photo together from the NZ Stuff video. There is more going on than Agent 666's screen grab shows.

This photo really makes things very interesting.

I believe this photo is taken just inside the balcony at apartment 1005 (level 10). It is the blind side to the image I showed (from the garden side) on an earlier post of mine. It definitely looks like a beam of sorts, but there appears to be two joint locations (possible 2 grouting beds) which would mean this beam may also be pre-cast of sorts(?)

The shear failure in the slab makes sense considering the following sequence of possible events:

1. Local failure occurs at the wall/grout immediately above the supporting columns under which is the point of most significant stress as pointed out by Human909's diagram earlier, which I'll re-produce here (I'm sticking to my theory of in-sufficient grout but for those playing at home who don't like blame to be given to the contractor this could equally be due to under-designed wall thickness or under-specified grout and/or wall grade from the design engineer!!).

2. Once local failure occurs over the support columns, load then wants to transfer itself, via bending, to the upstand beam and slab system (mind you both of which would not have been designed as transfer elements considering their small depth in comparison to apparent applied load).

3. The up-stand beam and slab however can not go into bending because of the significantly stiff wall above, therefore everything is taken out in shear at the critical failure planes some distance away from the internal faces of the support columns below.

4. The upstand and slab system can not take the shear load so they fail, in shear. Local shear failure would then mean that a portion of the level 10 slab at this location is now "hung" from the support wall above.

5. By this time, the wall has failed enough to increase its bearing contact area with critical surface of the up-stand beam, this is either through closing up of grout voids and/or blasting off enough of the base of the wall to be rid of the chamfer you often find at the base of panels to prevent cracking/chipping in transit, thus increasing its contact area.

6. Local failure of the wall means all levels above drop by however much distance the wall/grout crushed. This explains the Hebel destruction at level 10 immediately adjacent and reports of doors sticking in their doorjambs on levels above.

 

[human909]

I believe this photo is taken just inside the balcony at apartment 1005 (level 10). It is the blind side to the image I showed (from the garden side) on an earlier post of mine.

I think you are spot on with the location. In fact your own photo posted earlier gives context.

This is the same position just before they cleaned the area up properly exposed the beam and wall. It looks a fair bit different but note the same angles in the slab cracking.

Also going over some of the other photos. From what I can see they have engaged in floor to ceiling continuous propping in the floors below level 10 along grid line 20. Propping here makes sense but until I started piecing together the available pictures of the props this had been less clear.

I just thought I'd add a few pictures and what I believe is the context.
Floor plans Levels 5-9

I believe this is showing the bedroom 1, in apartment 3 on one of the floors 5-9. They seemed to have smashed through the Hebel wall separating apartment 3 from 4 to install continuous propping along grid line 20.

Bedroom 1, apartment 4, floors 5-9. (facing built in wardrobe and props going through Hebel wall)

Bedroom 1 apartment 4, floors 5-9. (facing window)

 

[Tomfh]

Sheer force eng, in the photo the grout bed appears the same thickness on both sides of the crack.

 

[Skogsgurra]

An outsider's view:
1. Will most of the building come down? Or are there ways of saving it?
2. If so, who wants to move in again?
3. This thread will, or has already done so, influence the direction investigations take. Which I think is a good thing. More questions and more views. It will be difficult to leave any stone unturned.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[human909]

1. Will most of the building come down? Or are there ways of saving it?

No (very unlikely). But we don't know the exact issue and have no indication of the potential extent. The remediation will be a costly nightmare, but likely less so than the alternatives.

2. If so, who wants to move in again?

That is the legal battle that is looming. Not just that but the loss of value will be a big battle ground the resale cost has dropped not matter what the fix. And there would be a decent number of owners who are investors or short term owner-occupiers. A class action is openly being discussed and discussions between residents and lawyers is occurring. (Property prices in Sydney have already dropped 10%, some might see this as a way of recouping losses already incurred.)

3. This thread will, or has already done so, influence the direction investigations take. Which I think is a good thing. More questions and more views. It will be difficult to leave any stone unturned.

No. On the engineering topics, the engineers involved are doing their investigation an have far more information than the tiny peep hole we have. On the legal and political stuff the media is keeping the spotlight on things.

 

[degenn]

ShearForceEng

A great diagram showing what has happened!

The interesting point is the crack in the lintel beam in vertical indicating a tensile crack. A true shear crack would be on an angle. The drop in the floor is a secondary effect.

The fact that is has tension suggests that the grout and shear connection has not failed. Otherwise the precast beam would just move in.

The fact that there is a single crack rather than spaced smaller cracks suggests it has less than 1% reo or it is not adequately anchored.

 

[rapt]

We must be looking at different cracks!