Partial Mall Collapse 7

[JAE]

dik,
I once was asked to look at some hollow core plank - the facility manager took me through an old abandoned plant - walked a ways across a large open room and down some stairs - underneath the very floor I walked I saw that the floor was comprised of hollow core planks - most of which had spalled the entire bottom "flange" off with multiple dangling strands hanging down as much as 15 feet. And I had just walked across it. This was an interior floor - no rain but probably daily washings as it was a meat packing plant.

 

[dik]

JAE:

Thanks for the added info... most damaged HC planks I've seen are at the ends or as a result of the core popping because of frozen trapped water... in this instance, I suspect that damage was due to movement or corrosion at the bearing ends.

Dik

 

[charliealphabravo]

i didn't see any sign of a vehicle in the photographs. that would suggest that the failure occurred under pretty minimal loads.

i'm with dik on the corrosion mechanism. the steel beam at the door looks pretty bad in the photograph. can someone with more HC experience confirm the direction of the span? it looks like the failed HC panels were supported at the door but this is opposite to the direction of the remaining panels in the photograph.

 

[dik]

The span appears between steel beams with HC slabs sitting on the flanges, and the grout space likely centred on the web. Usually, there are dowels between the HC panels (centred and perpendicular to the steel beams) I don't see any indication of these dowels in any of the photographs.

Dik

 

[ajk1]

While I agree that leakage of non-contaminated water does not lead me to think structural collpase, leakage of water contaminated with corrosive deicing salts certainly would lead me to believe that extensive structural damage has occurred if the leakage has been occurring for a number of years and yes IT MOST DEFINITELY WOULD MAKE ME THINK OF STRUCTURAL COLLAPSE if it is not quickly repaired, depending of course on condition survey findings. The corrosive deicing chemicals are tracked onto the roof surface from the cars. I would urge any engineers not familiar with this to read CSA S413. Hard to believe any structural engineer in Ontario is not fanilliar with this. If salt was directly applied to the roof surface as a de-icer, then it would have made things much worse.

It would be of interest to know whether or not there was water proofing traffic topping on this structure or not, and if there was proper slopes tpo drains and if the drainage piping we all clogged up. I suppose there was a membrane or it would have leaked like a sieve, but it sounds like it had gone beyond its design service life.
from day one into the occupied space below.


dik: it makes little difference whether the concrete is in compression or tension, with respect to protection of the steel. The corrosive chemicals are absorbed by the concrete and eventually penetrate to the steel, irrespective of whether there are any tension cracks or not. Sherway Gardens Mall parking structure was recently demolished; in that structure some of the strands were badly corroding at mid-span of the tees where they were in compression. What really drove this home to me was the Place Bell Canada garage in Ottawa in 1983 or so, which was heavily post-tensioned so that the yop was in compression just about everywhere and there were virtually no cracks in the top surface, yet the this had some of the most extensive corrosion of the top reinforcing bars that I have ever seen.

 

[dik]

ajk1... well aware of chloride intrusion, thanks... tensioning and density of the concrete just helps a tad... big thing is the integrity of the membrane.

Dik

 

[dik]

...from the Winnipeg Free Press, "ORILLIA, Ont. - New information has led the Ontario provincial police to deem their probe of a fatal mall roof collapse in Elliot Lake a criminal investigation.

Two women were killed on June 23 when the roof of the Algo Centre Mall caved in and plummeted two floors down into the building.

The provincial police force was assisting the Ontario Chief Coroner's office in its investigation into the deaths of Doloris Perizzolo, 74, and Lucie Aylwin, 37, but "as a result of information obtained," the police said Tuesday they are now also looking into the collapse as a criminal investigation."

 

[JAE]

Uh oh.

 

[dik]

It starts...

From the Globe and Mail, "A class-action lawsuit has been launched in relation to the fatal Elliot Lake mall collapse, according to a press release.

The release says that specific details of the lawsuit will be released this afternoon at the Elliot Lake Hampton Inn.

A source speaking on background said that the City of Elliot Lake, the province, and the mall’s owner will be party to the suit."

 

[hokie66]

Therefore, we may never get to see reports of any investigative work.

 

[dik]

At the trial, the reports will probably be entered in as the records and should be available.

Dik

 

[Hacksaw82]

Looks like they released the onigional engineering report here:

http://s3.documentcloud.org/documents/395566/algomallscan.pdf

The firm who did the report has been sighted for professional misconduct in 2010, according to reports. The PEO is said to be investigating this report, and the collapse.

 

[dik]

Thanks for the added info... I didn't see any dowels that are common between the HC panels and it may be that they were either cut in the caulking process by someone not aware, or possibly rusted at the HC joint, or maybe there just wasn't a picture showing them.

Dik

 

[Hacksaw82]

Yes, I noticed that too.

It's also curious that they couldn't see the underside of a lot of the planks, due to the insulation. Seems like we may have a bearing failure here, likey the ends of the precast may have rotted out, or a beam flange went away.

This incident may have deep reprocusions in our industry, where it comes to condition assessments, and the liability we take on after.

 

[dik]

...from the PEO:

As part of PEO's assistance with the investigation of the Algo Centre Mall collapse, the following message is being sent to all licence holders in the province on behalf of the Ontario Province Police (OPP). Please contact the OPP directly should you have any information to provide.


Ontario Provincial Police
Criminal Investigation Branch
Criminal Investigation Services
777 Memorial Avenue
Orillia ON L3V 7V3

Thursday, July 26, 2012

Attention PEO Members:

On June 23, 2012 the roof of the Algo Mall in Elliot Lake Ontario collapsed claiming the lives of 37-year-old Lucie Aylwyn and 74-year-old Doloris Perrizzolo as well as injuring 19 other people.

The O.P.P. is investigating the cause of the collapse with the assistance of members of the PEO, who are conducting the forensic analysis of the building from an engineering perspective.

Our investigation to date has indicated that there may well have been a number of engineering assessments done in relation to the Algo Mall, for various purposes, since it was built in 1979.

There are obvious challenges associated with identifying the engineers who have conducted these assessments over such a time span and with retrieving related information and reports. For this reason we are asking for the assistance of PEO Members to attempt to identify and speak with those who may have been professionally involved with the Algo Mall.

While this is considered a Criminal Investigation, our primary goal is to provide answers to the people of Elliot Lake and, most importantly, to the families of the victims, as to what led to this catastrophic building failure.

If you, a colleague or your company has conducted an engineering assessment of any kind at the Algo Mall, or if you feel that you may be in a position to assist, please call the tip line at:

705-849-7246 or by email: OPPELLIOTLAKE.ALGOMALL@ontario.ca

Any information provided will be treated with the utmost regard and attentiveness to the sensitivity of its nature.

I sincerely thank you for any assistance in this matter.

Detective Inspector K.M. (Mike) Bickerton
Ontario Provincial Police

 

[SkiisAndBikes]

From the Toronto Star ...

http://www.thestar.com/news/canada/...top-parking-lack-of-waterproofing-scrutinized

 

[JAE]

From that Toronto Star article - a key sentence:

What’s not clear is if any structural issues could have been detected by these visual inspections, or if more was or could have been done to test structural integrity.

What is everyone's perspective on this? I know that we are often times hired to perform "visual" investigations of structures and we write reports outlining what we can visually see - if there are any visible distresses, cracks, flaws, etc.

Are we as structural engineers required to, or "allowed" to stop at visual examinations? Is our pledge to protect the public safety and welfare something that would compel us to recommend to an owner to do more tests, load tests, material tests, local destructive demo to open more lines of visibility?

 

[dik]

S&B... good link...

Dik

 

[charliealphabravo]

What is everyone's perspective on this? I know that we are often times hired to perform "visual" investigations of structures and we write reports outlining what we can visually see - if there are any visible distresses, cracks, flaws, etc.

I'm interested in this deliberation too. The question is even more difficult with shear failures like this one that may be sudden and experience minimal prior displacement. It's enough to give you cold sweats if you try to imagine a scenario where there are no warning signs if there is such a thing. The Hyatt Regency might have been close from a third party condition assessment point of view.

Aside from any standards that may apply, I foster a "follow your nose" instinct. Based on what little we think we know so far, this one stinks enough that an engineering survey that started out as visual should have long ago escalated into something more exploratory, so I say. Thirty plus years of documented leaks coupled with a steel frame under a winter parking lot over a food court would make you curious at the least I think. Add some quick span and bearing checks, pull back some insulation, probe or sound the steel and I have difficulty believing you wouldn't be worried by that point.

 

[rowingengineer]

"Are we as structural engineers required to, or "allowed" to stop at visual examinations?"

YES. If the scope requires a visual then you provide a visual, and recommend further investigation as required from problems found from the investigation.

I don't subscribe to idea that as structural engineers we should go beyond our scopes in the name of good faith and NOT be paid for it.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."