"Doomed" Las Vegas Tower - Structural Blunders 17

[JAE]

Someone's in trouble...just not sure who:

Doomed Tower link

 

[a2mfk]

ahhhhhhh, I stand corrected. I was thrown off by: Perini Building Company's subcontractor, Pacific Coast Steel.

But I suppose rebar is steel now isn't it...

Carbon fiber maybe?? A whole lot harder to know exactly the field conditions when they are covered with concrete!

 

[azcats]

From what I heard, they did a lot of NDT to determine what was in place and that's how they determined where the new height would top out. It's a weird situation because the floors they removed were residential units that weren't selling and MGM is probably glad they didn't build them...and Perini knows this.

 

[ishvaaag]

Knowledge is not only difficult to be brought into the minds, it is also difficult to bring to the works. I perfectly understand that something as complex as our buildings and constructions are not entirely in the reach of almost anyone in the world. Yet traditional (middle ages) practice was that someone, a contractor-architect-designer, fared with the representation and risks of construction. Since then we have not made other thing that spread more and more abilities and liabilities between different trades.

Some of the "late" implementations such project managers and third party inspections may be -not neccesarily are- truly invasive and disruptive of the traditional ways, particularly in chain of command and some aperture to the "politics" and "economics" of getting commissions, fees, etc.

Not that this only happen to designers; european contractors may be forcibly required to bring the financing of big works or maintenance of the same for say 20 years, making the bank an uninvited guest to their dish.

I am wary of such aperture that can turn in a field of mines able to do away with entire sucessful, profitable and responsible practices and firms, and I have seen cases where these purportedly neutral interventions, and maybe protective of public interests, lead to the realization of the dangers above stated.

Particularly worrying is that some of the outfits are (sometimes transparently, i.e, "invisibly") manned by cheaper scarcely trained professionals, or even if trained, with so little practice or common sense that they themselves are a risk; everyone that can punch the cards, er, make the input to some program is already the nicest engineer.

In many cases, 3d party intervention is a logical requirement, and not even such concern as Foster's can think be logical to take it all to make something in Las Vegas in accord to customs and laws they are not customarily practicing (something entirely common for international practice except for delivering ready-made facilities, I think). Hence some must decide that from construction design and later they just better look from the distance. And sometimes must be a sight.

 

[JStephen]

It's really kind of hard to see through the spin here. If the reports in question just said everything was okay when it wasn't, is that a "falsified" report? Was there some kind of scheming going on with those reports, or just failure to recognize or call out problems? Was the steel placement a "blunder" or was someone following conflicting details along the wrong line of interpretation or what? You can tweak the wording on some of this and change the impact of the story considerably.

 

[JedClampett]

Plus, if you read the Las Vegas Review Journal article linked above, Perini is claiming that;
"Perini counters that structural drawings for Harmon 'were months late and contained many errors and omissions,' adding that MGM Resorts 'would have to acknowledge that the permitted set of drawings never matched the sets of drawings (used) to construct the project.'"
Was this project so rushed that they didn't have drawings to build from?
I think that MGM found out in the middle of the project that it was going to be a money loser. They're litigating their way to cover part of their investment.

 

[JStephen]

You know, this being in Vegas, they should just build it to the full original height, put a big sign out front that says "40% Chance This Building Will Collapse In The Next 50 Years- Do You Feel LUCKYYYYYY?" People would flock to it and buy the T-shirts.

 

[dik]

Rowingengineer...

ANY FOOL CAN DESIGN A STRUCTURE. IT TAKES AN ENGINEER TO MAKE THE CONNECTION."

Dik

 

[vanmorrison]

If the reports in question just said everything was okay when it wasn't, is that a "falsified" report? Was there some kind of scheming going on with those reports, or just failure to recognize or call out problems?

J, you received a star. You have made a very good point and I thank you! To be honest I assumed that the act of fraud and misrepresentation had taken place. Is this a fact or am I jumping to the wrong conclusion? Could the inspection have inadequate because of inspector ignorance or inspection criteria the inspectors are reporting to? Should I believe newspaper reporters as always correct who have verified their statements and context to avoid slander?

JedClampett, I gave you a star also. Yes, there are 2 sides to every story. It is usually the good ones that die first.

What are the requirements to become an inspector, how are the inspectors qualified, who qualifies the inspectors, who is overseeing the inspectors? What was the inspection criterion and did it include the issues deemed unacceptable?

I have a hard time believing that reporting errors (intentional of unintentional) where made by that many inspectors and everyone turned a blind eye to it. There is usually a whistle blower in the pack. Perhaps this is how the condition came to light and the whistle blower is now included in the Las Vegas 20% unemployment stats pointed out by DIK.

IMHO, fraudulent, intentional, misrepresentation of inspection results should be punishable by law, include a fine and jail time. Punishment should also be extended to the entity paying and employing the liar. I say this but on the other hand I do feel for inspectors who have a family to feed and want to do the right thing but are pressured or mislead otherwise.

 

[vanmorrison]

Call me crazy but I always like to have the guy who designed the building also to be the inspector.

I don't think you are crazy.

 

[abusementpark]

vanmorrison

And you get a star because I love your music!

 

[vanmorrison]

Abusementpark, thanks bud!

 

[JStephen]

In the video down on this page, they give an example of the steel placement problems:

http://www.fox5vegas.com/news/25805385/detail.html

 

[ishvaaag]

It frankly looks more an economical problem than a constructive one ... 1.5 billio dollars? The building seems not to have the size to recover such amount by any means.

 

[hokie66]

The video doesn't help much in understanding the problem. The language used ("reinforcing the cement"), etc. doesn't give any confidence in the reporting. The other reference talks about congestion in beams which are 8' thick, which may mean 8' deep, but that is just a guess. The most common place for congestion problems in towers is in core coupling beams and outriggers...

 

[paddingtongreen]

From the video, it seems there were two rows of bottom reinforcing but the constructors took some from the centers of the rows and put them higher up on the sides of the beams. It sounds as though there was a large proportion of steel, probably lots of stirrups near the ends making it difficult to add the inner bars.

We used to build physical models of some congested joints in a couple of the nukes that I worked on. It made planning the rebar installation so much less difficult.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[abusementpark]

These quotes from Hokie's article tell the story, I believe:

They found that the Harmon's third-party inspection firm, Monrovia, Calif.-based Converse Consultants, falsified 62 daily reports between March and July of 2008 stating that things were OK when they weren't. County inspectors missed the problems, too. It seems rebar was misplaced inside link beams that transfer horizontal loading to the building's shear walls. A shear wall is a braced panel wall that counters lateral loads on a structure. In other words, it supports the building and keeps it from falling over.

Stirrup hooks, ties that hold rebar together, also were spaced incorrectly, county investigators found; some even poked past the floor slab, prompting workers to cut them off with a blowtorch so they wouldn't show.

"We do not see this very often," county building official Ron Lynn said. "They installed it wrong. That's the bottom line."

Harmon's design called for pouring top portions of the 8-foot-thick link beams with the floor slab, which is a tricky procedure given the tight and exact spacing of rebar.

Harmon workers reportedly moved rebar without first getting an OK from the structural engineer, Halcrow Yolles, which is a major no-no in the construction chain of command. Rebar placement is carefully configured to maximize structural building strength.

"Congestion, or too much rebar matted together, prevented proper coverage and distribution of concrete," said a project official who requested anonymity.

Perini counters that structural drawings for Harmon "were months late and contained many errors and omissions," adding that MGM Resorts "would have to acknowledge that the permitted set of drawings never matched the sets of drawings (used) to construct the project."

While it doesn't quite sound like the structural engineer is completely off the hook here, there seems to be a lot of overwhelming evidence that the rebar sub and the inspectors were the major culprits here.

How this went on for 15 floors of construction is beyond me. Did the EOR not made a single pour visit the entire time? I understand sometimes you are specifically not hired to perform construction administration. However, on a building of this magnitude, an engineer should never allow complete separation from the construction process.

Oh well, at least it was a successful project for the lawyers.

 

[paddingtongreen]

It was my practice to consider constructability in my designs. Over the phone, or in a meeting, I would tell the fabricator/erector, off the record, what I had in mind when i made the design. I would tell them that I would make changes to accommodate different "ways and means".

Then, after the lawyers and the insurers became involved, we were instructed to stay away from means and methods, it belonged to the Contractors and our insurance didn't cover it. The weird thing though, was that one of our construction managers would look it over for an independent QA constructability review. Unfortunately, they were senior, desk-bound guys who hadn't been in close proximity to actual construction work for eons.

Oops, this started out as a caution, the GC says they were working to drawings different to the sealed permit set. We don't know if the EOR was consulted about the changes. We don't know what drawings and documents the Inspectors were using. It looks certain that the owner miscalculated the demand for condos and is trying to call it a loss due to the faulty work, etc. etc..

A personal note; I hated working on jobs implementing the designs of "Great Architects".

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[DRC1]

"...the permitted set of drawings never matched the sets of drawings (used) to construct the project."

Considering the terrible housing and construction market in Las Vegas, and without saying which parties were at fault, how could anyone expect the above situation to end well?

 

[JAE]

A personal note; I hated working on jobs implementing the designs of "Great Architects".

A star paddington! - I've seen the same frustration - but that struggle is either because:

1. The "great" architect was really quite incompetent when it came to constructable details, or,

2. The "great" architect was designing something unique, and in doing so was pushing the engineers to stretch their designs as well and design something unique as well, or

3. a combination of 1 and 2 above.

 

[JedClampett]

One thing that confuses me (actually a lot of things confuse me) is on the news story that JStephan linked. I realize that there is nothing more superficial than a local TV news story. But the example the construction professor shows in the story was that the horizontal bars in the shear link(?) were incorrectly placed and the stirrup (tie?)spacing was too far apart. If that were my project, I would be doing some serious pencil sharpening to make that work. If the links are tension members, is the bar location and stirrup spacing really that important? And isn't there some room for interpretation either way? Note that Las Vegas is a pretty low seismic area, corresponding to the old Zone 2B.
With hundreds of millions of dollars at stake, I wouldn't mind getting a cut of it to do an as built analysis of the structures. It seems that tearing them down is pretty drastic. Fifty or sixty million dollars in repairs could go a long way.