Who is Responsible?

[dik]

Further to a current thread and not wanting to hijack anything:

The Algo Centre mall that had the roof collapse and kill a couple of people and injure 20 more had a non-construcable roofing system that was ultimately the cause of the collapse. The roof was used for parking over the mall area.

Who would normally be responsible for the roof construction? The Architect, the engineer, or the precaster?

I would consider the roof as part of the building envelope with the Architect responsible for waterproofing and control joints. He would normally work with the engineer on this. I've also encountered the precaster looking after the entire topping, membrane and control joint issue, but only for stand alone parkades.

Just looking for some other thoughts.

Dik

 

[civeng80]

When it ends in a Court case or Inquiry all of the parties would become involved to give their evidence.
It could be one or or three that could ultimately be responsible.
The Laws of the Land are not always compatible with the laws of nature !

 

[rowingengineer]

Whomever had it in there scope of works/contract.

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."

 

[aaronPTeng]

dik,

I believe it is the engineer. Architect a little bit also. As an engineer you need to take into account the conditions your structure will encounter. the architect should also be responsible for water proofing and should detail the drawings accordingly. However as the engineer you assume this will eventually fail, as water proofing is generally warranted for 10 years and your design life of your structure long exceeds this.

As an engineer you need to understand the construction methods and the skill set of builders in your area. You then factor this into your design.
It is noted in a news article the engineer mentioned he was not happy with the construction, then simply he should not of passed it. We have all been in situations where there is pressure as we all have to run a business. But at the end of the day your a professional engineer and the buck stops at you.

Although who is responsible is all irrelevant in the legal process. They will chase the money and the easiest target. They will go after everyone until someone blinks first and insurance pays up.

"Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. Dykes, 1976

 

[aaronPTeng]

http://www2.elliotlakeinquiry.ca/exhibits/mar_12_13/NL_E000010274.pdf

Good link for the report.

"Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. Dykes, 1976

 

[hokie66]

The architect traditionally has been responsible for ensuring that buildings shed water. But today, architects seem to think that they only need be concerned with floor plans and aesthetics. In the disgraceful case of the Elliot Lake collapse, there was plenty of blame to spread around. As Dik said, the roofing system as built never had a chance, but then plenty of supposedly competent engineers, inspectors, etc. had chances over the years to do something before it was too late.

 

[dik]

I've gone over the forensic report in some detail. Some added info to the OP (based on info contained in the report).

Roof construction specified was essentially a 3” concrete topping supported on a waterproof membrane and 8” hollowcore slab. Stipulated loading was for a superimposed load of 140 psf and the maximum span was 31’-0”. Actual construction consisted of a repairing cracking in the 3” composite topping. I've used 8" HC for 32' with no topping and a 40 psf live load, just about maxxing it out.

Structural steel shop drawings were reviewed by the Architect only, and hollowcore shop drawings, bearing the seal of the precaster’s engineer, were returned, not reviewed.

The drawings were prepared by the Architect, but sealed by the engineer. The drawings essentially stipulated the design loads.

Dik

 

[cliff234]

This failure, like most, is a classic case of several mistakes coming together to cause a structural failure. Lack of communication, complacency and inattention to detail. Like most structural failures, valuable lessons could be learned from this tragedy by everyone in our profession.

 

[msquared48]

At a 31' span, with a 2.5" slab, 8" hollow core is only good for about 70 psf here.

Someone (is) screwed up there...

Mike McCann
MMC Engineering

 

[hokie66]

Maybe the structural design wasn't very good, but the building finally failed due to corrosion of the steel, and that was caused by leakage. As Dik said, there was no membrane, and it all depended on continually replacing sealant and hoping. Nobody did their job in a professional manner.

 

[dik]

The connection that failed was reduced to 13% of its capacity due to corrosion. Cyclical loading and no mention of fatigue in the report.

During construction when the engineer was questioned by the client about the design, he responded by saying that the drawings showed the stipulated loading and it was the precaster's responsibility to provide it.

Dik

 

[Ron]

dik...good thread.

I've gone over the forensic report in some detail.

This is exactly why you'll not likely ever be in the position of the project's design engineer and others. Case histories and failure investigations/forensic studies teach us so much about the expanded effect of our decisions, lack of decisions and project interactions.

This one is clearly a waterproofing failure first, followed by a weak structural design. Chances are though, that absent the corrosion issue, the structure would have performed a long time since structures rarely are exposed to the loads for which we design them.

I agree that waterproofing should be an architect's purview; however, as hokie66 correctly noted, they seem to want to abdicate responsibility for anything not aesthetic. Unfortunately the same theme plays out throughout construction....delegate of activities and responsibilities with no follow up or interaction

 

[dik]

It may be more of a material and design failure. It's an interesting problem... the office manager sent out a link to an animation of the collapse... so, I took a gander. I then decided to get a copy of the forensic report for a quick read... and found so many 'interesting' things (in a Chinese sense) in it that I decided to do up a powerpoint presentation. This became three presentations. I uploaded the first in the ET Journal section for forensic reports. The project became so large that I did the general forensic report preparation, the critique of the submitted report and a third one that offers my own comments and observations.

The spec'd roof wouldn't work, you would likely get 1/3 the stipulated superimposed loading. As constructed, with a 3" composite topping, you would be hard pressed to get the specified 140 psf load capacity.

The jointing in the 3" topping was critical... if you can imagine a 3" concrete topping several hundred feet in both directions relying on sawcuts spaced too far with no time control for the 'cutting' to provide the 'leak' control. The parkade roof leaked the first year and continued for its lifetime. It was never properly repaired. Cracks occurred at 'random' and were caulked, sometimes using improper caulk. The aspect ratio of a caulked repair is generally too 'rigid' and forces the caulk to fail, or tear away from the concrete. People involved did not seem to have any understanding of the problem.

The drawings were never revised to reflect a proper construction, and, I suspect numerous good consultants that prepared reports had assumed the original construction was adequate. The consultants include some of the better engineering firms and they are well versed in parkade deterioration/corrosion issues. The inadequacy was not included in their reports.

The reason I'm thinking that it could be more architecturally related is that the drawings, including the structural, were prepared by the architect. In addition it does not appear that the engineer was even involved with shop drawing review. This was handled by the architect.

I've done 12" HC parkades with composite toppings, but each second HC joint was tooled (so it is installed at the correct time) and filled with urethane sealant. This was alternated with a proper joint with a bond breaker that was 2" wide. It's still standing...

 

[hokie66]

How can a topping be both composite and have sealed joints? Doesn't make sense to me.

 

[dik]

for example with 4' wide planks, the joints are at 4' with tooled and bond broken joints alternating at 4'. By tooling the joints, you guarantee that they are installed at the right time <G>. In the other direction, the joints would be at 31' with the composite topping in compression... The joints are parallel to the span.

The original had 8" HC with a membrane and a 3" topping... no composite action possible due to the membrane.

Dik

 

[hokie66]

Silly system, as far as I am concerned. Either the original or the actual.

1. In the original, there was probably no drainage at the membrane level, whatever the membrane was supposed to be. And no way to tell where leaks are occurring in the membrane.

2. In the actual, depending on a bonded topping and sealant joints is a recipe for disaster. Concrete isn't waterproof, and sealant joints require a lot of maintenance. May be something that could be dealt with if the area below is accessible, so that leaking is apparent immediately. But if this is parking over a habitable area, I would worry.

 

[dik]

The slope in general was less than 1%... another 'no-no' for a parkade structure... At very least, they should have had a bonded topping for strength if necessary, an insulation layer, another concrete topping and a waterproof membrane, properly sloped... then it might have worked...

Dik

 

[dik]

...or the membrane beneath the concrete topping... to help protect it.

Dik

 

[aaronPTeng]

hokie, dik,

I often say to builders/ developers, not to rely on trades to do the job properly. Therefore yes have a membrane documented but also design the structure in critical areas like above to be water tight, or shed water etc.

If we know this is an issue shouldn't we be designing our structures with this in mind?

Maybe it is showing i do not have that many grey hairs and was not around when architects used to document to high levels,

Regards,

"Structural Engineering is the Art of moulding materials we do not wholly understand into shapes we cannot precisely analyse, so as to withstand forces we cannot really assess, in such a way that the community at large has no reason to suspect the extent of our ignorance." Dr. Dykes, 1976

 

[hokie66]

aaronPTeng,

Often it is not feasible, at least not practical, to design a structure to be watertight. That is where the cladding, facade, waterproofing, etc. come in. So making a building shed water was traditionally the responsibility of the architect. Not so much in recent times, with more complicated buildings. Now we have facade engineering as a specialty, and few architects want to be involved in the actual detailing. The philosophy seems to be that if a detail is not shown, the architect can't be blamed if it doesn't work.

In the case of the Elliot Lake shopping centre, there were plenty of people who all needed to work to the same end if this disaster were to be avoided. The architect, structural engineer, precaster including the designer for that system, structural steel fabricator and erector, the so-called membrane designer and installer, maintenance people, various inspectors, local authority staff, several successive building owners...

As the NORR report stated, this was an "intrinsically flawed system", and that should have been evident to many people along the way, assuming they had a modicum of common sense.