Metrodome Roof Collapses?

[grizz441]

You hit the nail on the head for me Shuffler.  I got roped into running a program that designs structures 4 years or so ago.  Fortunately I've had the guidance of a PE I've worked with for almost 15 years and he's helped a LOT.  As I'll never actually be a full blown structural engineer I try to learn as much as I possibly can about it.  Not only in my area but as many other areas as I can.  Which is why I'm bugging Grizz and Sunbat as much as I can (sorry guys). 

correct, Sunbat and grizz since Sunbat has been a licensed structural engineer for a while now.  I'm just a wee old EIT working to become licensed in the future.

[grizz441]

I'm figuring like anything else. You learn it the hard way in school then when in the job arena you have computers do most of the calcs. You must be able to understand what is being done though.

You have computers do a lot of the hard calcs, but you have to know how to model.  It's not as simple as just magically creating a structural model and then clicking a button that gives you the answers.  It is difficult stuff and you have to know what you are doing to make sure that you make the correct estimates and boundary conditions.
I'd say I do about 60% of my calculations by hand though, especially when sizing individual members.  When you look at more complex systems of multiple members acting together, computers become necessary.

[SunBat]

You hit the nail on the head for me Shuffler.  I got roped into running a program that designs structures 4 years or so ago.  Fortunately I've had the guidance of a PE I've worked with for almost 15 years and he's helped a LOT.  As I'll never actually be a full blown structural engineer I try to learn as much as I possibly can about it.  Not only in my area but as many other areas as I can.  Which is why I'm bugging Grizz and Sunbat as much as I can (sorry guys). 

I felt a little bad about making that statement to Babalonian about “CADD monkeys” because there are many many designers that I greatly respect.  I actually don’t like that term  (I had to rib him some though ).  As a matter of fact, the very guy that got me into Aces High was one of the best designers that I have ever worked with.  He used to be on the boards a lot, his name was Yknurd and his in game name was Drunky.  He was a designer much like the way you seem to be, he was always interested in learning and would have been a fantastic engineer but his circumstances in life never allowed him to make it to college and get a degree.  He is smart as a whip, truly gifted with a tremendous capacity for spatial reasoning, has intense focus, and has that proverbial “snap” that is so cherished in our line of work.  I have had the privilege of working with others like him and I am absolutely convinced, and nobody will ever be able to persuade me otherwise, that an engineer’s number one most valued asset is a good designer.  You sound like that type of person, so keep up the good work.

And don’t let Grizz fool ya, one day he will make twice the enginerd that I am.   

[Dichotomy]

Thank you SunBat..   I remember Yknurd any idea how he is?

[Babalonian]

<snip>
Oh, and your definition is incorrect.  Carry on though cad monkey. 

No... no, I think I'm correct.

I vote that we get Skuzzy in here to weigh on the final and absolute decision. 

The Gerhardt I'm talking about has a young kid, he went to a school that my mom taught at.

He also has a very thick German accent

Probabley not him, he doesn't have an accent at all... though, it might not be noticable given the super-thickness of the accents of some of the middle-eastern guys/gals working there.

[Babalonian]

I felt a little bad about making that statement to Babalonian about “CADD monkeys” because there are many many designers that I greatly respect.  I actually don’t like that term  (I had to rib him some though ).  As a matter of fact, the very guy that got me into Aces High was one of the best designers that I have ever worked with.  He used to be on the boards a lot, his name was Yknurd and his in game name was Drunky.  He was a designer much like the way you seem to be, he was always interested in learning and would have been a fantastic engineer but his circumstances in life never allowed him to make it to college and get a degree.  He is smart as a whip, truly gifted with a tremendous capacity for spatial reasoning, has intense focus, and has that proverbial “snap” that is so cherished in our line of work.  I have had the privilege of working with others like him and I am absolutely convinced, and nobody will ever be able to persuade me otherwise, that an engineer’s number one most valued asset is a good designer.  You sound like that type of person, so keep up the good work.

And don’t let Grizz fool ya, one day he will make twice the enginerd that I am.   

Don't worry about it,  every monkey has his day.    I'll come up with something more witty nexy week, I'm preparing to take home some work I gotta hump over this weekend to meet a noon deadline on monday (that some 4-year degreed nupty inadvertently forgot to mention to me until last night, even though they knew about this deadline three weeks ago.... lesson for today kids; stay in school longer so you can enjoy your weekends, get paid twice as much, work half as hard, and deligate the overtime... am I mad?  F-no, today is payday and tonight I PARTAY!).

[Tordon22]

multiple members acting together

Is that your favorite part?

[cattb]

Could the amount of wind moving snow on the metrodome roof have something to do with the collapse?

Some area barns where I live had the roof collapse. They were newer buildings. Besides the heavy snow load, there was so much wind that one side of a roof had very little snow and the other side would be stacked high with snow. Just to the south 16.6 inches of snow and about 30 miles north about 22 inches snow of where I live.

[grizz441]

Could the amount of wind moving snow on the metrodome roof have something to do with the collapse?

Some area barns where I live had the roof collapse. They were newer buildings. Besides the heavy snow load, there was so much wind that one side of a roof had very little snow and the other side would be stacked high with snow. Just to the south 16.6 inches of snow and about 30 miles north about 22 inches snow of where I live.

Windward or Leeward drifting (worst case) is to be superimposed on balanced snow load if an obstruction like a high wall or parapet exists.  There are provisions for that, I'm not sure how that relates to a dome structure, but the engineers who designed it should have found out.

[DREDIOCK]

I used to think the PE registration process was absurd until I read this thread. Thank you for making my PE registration mean something Dred, et al.  I was afraid I went to school, practiced engineering for all those years, and passed that impossible test for nothing. Please keep drafting for dollars and imagining that u know what ur talking about while the real engineers make sure the public is safe.  Please.

It doesn't sound like you have a very good understanding on how the engineering world works.  Just sayin.

Ok. Rather then put up the text that immediately came to mind.
Explain to me my errors.

Im not an engineer thats true And true I dont have a full understanding of engineering. But I do get to be in the maintenance end of the work and can see what seems to be to be common sense reasoning.
Given the typical environment of the area. The dome was doomed to fail. Fortunately the failure wasnt worse and nobody was in the way, or on top when it did. which could have very easily happend considering that just hours earlier people were up there trying to clear it. You cant just let that much snow sit on top of something like that Let alone wet snow. Eventually something is going to give. You dont need to have an engineering degree to figure some things out
I bet if you had interviewed some of the maintenance workers even months ago. they would have predicted this to happen at some point.
You see. engineers design it. But the workers have to deal with the finished product hands on day after day.

Suns. How many wakes and hospitals have you been to that were caused by your superior engineering skills?
How much time have you spent on the maintenance end of some of your designs?
Engineers are capable of great accomplishments and horrible disasters. Sometimes within the same projects

It becomes dangerous when you have engineers who seem to think they have a lock on safety





Sun. based on your comment. I'd have to say you are possibly one of those liabilities

[DREDIOCK]

Windward or Leeward drifting (worst case) is to be superimposed on balanced snow load if an obstruction like a high wall or parapet exists.  There are provisions for that, I'm not sure how that relates to a dome structure, but the engineers who designed it should have found out.

Dunno if you have read this already or not. but ti gives some eplanation as to how the dome was supposed to work

http://engineeringfailures.org/?p=391#more-391


and in this post not trying to sound like too much of a wisearse but
Again I am not an engineer. But anyone who has ever had to shovel slush can tell you there is a slight difference in weight between wet snow and what is often called "dry" snow.
A better example of what Im trying to say is after a storm with a very cold snow how much lighter the snow is to move then if you wait for it to start melting.
This is because of the amount of air trapped between the flakes. the water content can range from 3% in a very "dry" snow to 33% in wet snow to 100% for ice
Again. using common sense. they were melting the snow from underneath. then steaming it also from above adding even more water to an already wet and heavy situation. This on what was from what I have read an already very wet snow to begin with thus removing the air from the snow making it even heavier in a more concentrated area.
Now I know this is a much different structure. But on a house the last thing you want is for the the snow to melt in such great amount on your roof. Ideally you want your attic and roof to be the same temperature as the outside

Referring back to the pictures I used in my original post. It would seem to me a far better design to simply create a roof with such a pitch as would simply not allow great amounts of snow to accumulate up there to begin with.

Now. if I am wrong. explain why.

[SunBat]

Suns. How many wakes and hospitals have you been to that were caused by your superior engineering skills?
How much time have you spent on the maintenance end of some of your designs?
Engineers are capable of great accomplishments and horrible disasters. Sometimes within the same projects

It becomes dangerous when you have engineers who seem to think they have a lock on safety
(Image removed from quote.)

(Image removed from quote.)
(Image removed from quote.)

Sun. based on your comment. I'd have to say you are possibly one of those liabilities

Um.  None, thankfully.  I also don’t remember making a statement that implies that I think I can never make a mistake.  It’s a good thing for an engineer to make the person that he/she trusts the least be themselves. 

There is no way for me to go into any detailed explanation of the intricacies of structural engineering.  For me to do it any justice, I would have to impart to you the equivalent of at least four years of ABET accredited education and many years of practical engineering experience in addition to that.

I said earlier in the thread that I would withhold my opinion of this case because I know how intricate and detailed these things can be and it is impossible to know all of the factors involved just sitting at my computer and guessing.  This is the major distinction between me and you.  You made a post with “authority” about how it should be done, and I know there is way too much to be considered for me to pass judgment based on what I read over the internet. 

That’s the problem with people like you.  You think you know, and you make decisions and judgments based on what you think you know.  I actually won’t say until I do know.  Most good engineers won’t pass judgment until they have taken the time to sit down and analyze all of the factors involved in a design or situation.  That drives maintenance people, project managers, plant operators, facility owners, construction hands, fabrication technicians and drafters crazy because they think they know better than the engineer.   They don’t.

I can’t tell you how many times in my thirteen years of engineering experience I have caught a construction hand or a maintenance person modifying my design to such an extent that it really could kill someone.  Thankfully I had the way to check on them and not leave them to their own devices where they were sure they were correct and I was the “idiot”.   In most of the “engineering” failures that you hear about in the news, it is not the engineer that messed up but some slipshod construction outfit or maintenance person that decided to take a short cut when they were installing or maintaining the engineer’s design.  I would be willing to bet that that was the case with a lot of those pictures that you posted. 

[grizz441]

Dunno if you have read this already or not. but ti gives some eplanation as to how the dome was supposed to work

http://engineeringfailures.org/?p=391#more-391


and in this post not trying to sound like too much of a wisearse but
Again I am not an engineer. But anyone who has ever had to shovel slush can tell you there is a slight difference in weight between wet snow and what is often called "dry" snow.
A better example of what Im trying to say is after a storm with a very cold snow how much lighter the snow is to move then if you wait for it to start melting.
This is because of the amount of air trapped between the flakes. the water content can range from 3% in a very "dry" snow to 33% in wet snow to 100% for ice

This is already common knowledge and factored into design Dred.  This isn't common sense stuff that the 'idiot engineers' didn't think of.  Here is the design equation for the density of snow:

γ = 0.13pg + 14 but not more than 30 pcf

pg is the ground snow load, and is 50psf for Minneapolis.  Do the math, and compare that number to the density of water and see what you come up with.  It's not like this "wet snow" thing is something the "idiot engineers" didn't think of.

I can't even comment on the design of the dome, I haven't the slightest clue about it, or the designed drainage system, or its required maintenance schedule. 

I'm curious though, what point are you trying to make?  That structural engineers are over payed idiots? 

[Dichotomy]

Dred,

As I believe I've posted before in this thread nobody will know for sure what the CAUSES of the incident were until the full report is filed. 

Suffice it to say that, based on discussions with PE's that I know and respect, my own thoughts, and the thoughts of others, the ultimate cause of the incident is fairly obvious.  The reason for that happening is not so obvious.

Oh and Sunbat... 'Project Designer' I like that title.  I'm, seriously, going to ask my boss to put it on my business card underneath 'Project Manager', 'IT Director' (laughing is okay I do), and 'Sales Manager'.  He balked at 'Head Number One Doo Doo Boy' 

Back to seriousness.  When I drive past or see something I designed I tend to grin thinking back and saying 'who would have thought I'd be doing this 20 years ago'.  My aim is to make damn sure that what I design is safe and standing until the owner decides to remove or replace it.  I can recommend certain steps that the owner needs to do to maintain the structural integrity of the structure but I'm not in the position to demand it.  If they dont.. well there might be averse consequences of their failure to heed my advice.

I can't and won't go any further in a public forum other than to say I trust the engineers I work with and know, if I miss something, they'll point it out to me and I can make corrections.  Imagine what it would feel like knowing your seal was on something that failed catastrophically due to causes unknown.  The engineer in question is guilty until proven innocent.  Tends to make MOST of them careful. I know I am and I'm just a project designer

For Sun and Grizz..  A couple I did that I'm kind of proud of. 




The second one is interesting because it's an embedded pole in a 15 ft berm.  Got a TON of schooling from my PE buds on that one.  Wish I could find the construction pics of the first one. 

[68ZooM]

I can’t tell you how many times in my thirteen years of engineering experience I have caught a construction hand or a maintenance person modifying my design to such an extent that it really could kill someone.  Thankfully I had the way to check on them and not leave them to their own devices where they were sure they were correct and I was the “idiot”.   In most of the “engineering” failures that you hear about in the news, it is not the engineer that messed up but some slipshod construction outfit or maintenance person that decided to take a short cut when they were installing or maintaining the engineer’s design.  I would be willing to bet that that was the case with a lot of those pictures that you posted.  

There lies the whole problem, it's "trying to save a buck" that leads to Structural Failures, like you posted deviating from an Engineered plan to save a buck or cut a corner is not worth a human life, just glad that no one was hurt when the Roof did collapse, all this discussion has really perked my interest in finishing my last 2 years, but oh i hate all the Math