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  #1  
Old Posted Nov 22, 2011, 4:07 AM
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Skyscraper loses windows in windstorm, what next?

If a skyscraper loses several windows in a windstorm, what happens afterward?
Aside from the obvious, namely the repair job.
Would the city get involved, sending out inspectors? Would an investigation be done to determine why the windows failed? (could be as serious as structural instability/excessive flexibility, or as minor as a manufacturing defect in the window, or improper installation)

This has happened before. Most notably to the John Hancock Tower in Boston, which had so many windows replaced with plywood at one point that it was a pitiful sight. On april 11, 1976, One Penn Plaza of NYC lost several windows in winds of around 35 mph. Nobody was hurt, but apparently the streets below were a mess.
In the John Hancock's case, the building did turn out to have structural issues, as well as defects in the glass itself, if memory serves. In One Penn's case, I have not found any info on a possible cause, aside from the aforementioned wind. But since 35 mph doesn't seem like that much of a wind to be knocking glass out of a building, I would suspect that perhaps there was something wrong with a few windows, or an installation problem. Overall, the building itself was fine.
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  #2  
Old Posted Nov 22, 2011, 10:15 PM
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This seems to be getting lots of views..
Nobody knows how incidents like this are handled, or what kind of response they might get?
Anyone know where I can find out?
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Old Posted Nov 22, 2011, 11:32 PM
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Since this is an issue regarding the diagnosis and correction engineering flaws in a building structure, the most likely route towards correcting the problem would be via a forensic engineering investigation. Most municipal building inspectors are trained only in pointing out quantitative flaws based on building codes (such as noting inadequate fireproofing, emergency lighting, etc.) from their rather brief visits to a building, so they wouldn't be the ones to carry out the investigation. It would most likely be done either by a private consulting firm, or by the firm(s) that did the original engineering and design for the building.

I think you answered the question yourself - the problem could be due to excessive building structural flex*, or it could be due to improper window anchorage design or installation, or it could be something else. But you can't say for sure which is the major problem that needs to be addressed until you make a thorough investigation of the building under wind conditions.



* For skyscrapers, whose primary lateral forces are due to winds, some degree of structural flex is necessary. But modern engineers try to avoid the difficulties in designing a building structure to withstand high wind loads by aerodynamically designing the building to simply avoid the winds, and therefore, relax the wind load requirements on the structure. This was done for the Burj Khalifa tower by designing the building so that its floor area becomes gradually smaller as it goes higher, as well as by the design of the setbacks. I believe the design of the setbacks allowed for the winds to circulate counterclockwise or clockwise around the building. Don't remember which.
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Old Posted Nov 23, 2011, 3:44 AM
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Is 35 mph (As in the One Penn Plaza case) considered a large wind load? Doesn't sound like it to me, but I'm not an engineer. And if it turned out that One Penn Plaza had something worse than a few defective windows, surely there would be something on public record? After all, the structural problems with the John Hancock building became common knowledge, and even the problems with Citicorp of Manhattan eventually became known.
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  #5  
Old Posted Nov 25, 2011, 3:43 AM
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Quote:
Originally Posted by Amanita View Post
Is 35 mph (As in the One Penn Plaza case) considered a large wind load? Doesn't sound like it to me, but I'm not an engineer.
No. The maximum design wind for NYC is 100-110 mph. It's quite conceivable that NYC gets hit by a hurricane, as we nearly saw with Irene this summer.
http://www.windspeedbyzip.com/

Quote:
And if it turned out that One Penn Plaza had something worse than a few defective windows, surely there would be something on public record? After all, the structural problems with the John Hancock building became common knowledge, and even the problems with Citicorp of Manhattan eventually became known.
Yes. That is not something that engineers would allow to be kept secret.

Incidentally, Robert Byrne wrote Skyscraper, a novel about this kind of thing. A brand new office tower starts shedding windows, and an engineer is brought in to investigate. During the course of his investigation, the engineer discovers severe structural flaws in the building and its foundations. He fights with the building owner to release the information because it is his professional duty as an engineer. I realize that it's an idealized, fictional case, but that is what is supposed to happen.
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Old Posted Nov 23, 2011, 3:56 PM
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This reminds of the Hancock tower case in Boston. Shortly after completion, the windows started popping off en mass. An investigation was carried out to figure why. Hancock tower was one of the first towers to have an all glass curtain wall. AS such, the engineers who designed had very little experience with the kind of glazing required for the very large panels of glass in tiny mullions. It turned out that the glass right next to the soldering wasn't strong enough.

However, the investigation into why the windows were falling off also revealed that the tower had insufficient wind bracing!

Edit:And apparently I didn't fully read the first post.
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  #7  
Old Posted Feb 25, 2012, 2:35 AM
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Quote:
Originally Posted by scalziand View Post
This reminds of the Hancock tower case in Boston. Shortly after completion, the windows started popping off en mass. An investigation was carried out to figure why. Hancock tower was one of the first towers to have an all glass curtain wall. AS such, the engineers who designed had very little experience with the kind of glazing required for the very large panels of glass in tiny mullions. It turned out that the glass right next to the soldering wasn't strong enough.

However, the investigation into why the windows were falling off also revealed that the tower had insufficient wind bracing!

Edit:And apparently I didn't fully read the first post.
Sorry, but this is incorrect.

The reason the windows failed on the JHC was because when they did the wind tunnel testing and engineering, they neglected to take into consideration the rest of the buildings surrounding it in the city!

The initial modeling and calculations were done with a stand alone building isolated in space!

Once they added the buildings to the testing model, they discovered the wind loading was severely inadequate, and adjusted their calculations accordingly, and everything was successfully completed.

It was not inadequate "soldering" or "gasketing" or size of the window panels - it was the whole installation "concept". And, no, the people who provided the installation were quite experienced in this sort of thing. They did not change the concept of the building structural "bracing" either.
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  #8  
Old Posted Nov 23, 2011, 5:05 PM
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And One Penn Plaza is another with a mostly glass skin, although I think the mullions are a little larger than on the John Hancock. And it went up around the same time, opened in 1972. In the Hancock's case, its structural flaws were corrected with additional bracing and a tuned mass damper.

I wonder how much One Penn moves around in a good windstorm? Too bad nobody here works on its upper floors
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Old Posted Nov 24, 2011, 9:27 PM
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A window shattered on one of the upper floors of the Austonian in Austin a month ago or so. They said they believe a large bird got caught in an updraft and hit the building. That was about 7 months after at least 4 windows cracked and fell from the balcony barriers at the W Hotel & Residences a few blocks away. All the glass panels from the balconies were removed and replaced this summer. It was thought that the summer heat this year had something to do with it.

I'm not sure that the city stepped in, other than to close the streets around the building. At least one panel damaged a car and shattered glass injured some people at the hotel's pool deck.
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  #10  
Old Posted Nov 25, 2011, 6:49 AM
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^I didn't think that 35 mph was that much. So that would most likely suggest a few defective or poorly installed windows, rather than a problem with the whole building, right?

And yes, I have read Robert Byrne's "Skyscraper". Good book, even if the ending is kind of sad for us skyscraper-lovers.
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