Metro Dome collaspe

[NITTANYRAY]

If I remember correctly, this is not the first time they have had trouble with snow on the Metro Dome roof.
I am sure the building code in Minn requires roofs to support more than 17" of snow.
Did the owners get a special variance because the roof is supported with internal air pressure?

It appears that when the roof deflated the snow on the roof all went to the center and caused a tear in the fabric.
I hope when they repair the fabric that they reinforce it in the center in case it deflates again.

 

[NITTANYRAY]

Yes it was a maintenance thing, but it was also a bad design.
If you design a parking garage in the snow belt but do not specify epoxy coated re-bars and it starts to rust in ten years is that a design or maintenance issue? Yes there are maintenance things the owner can do such as wash down the traffic aisles to remove the salt and replace the concrete sealer every five years that will increase the service life of the structure but specifying the correct materials and detailing the slabs so they drain properly is also a big part of the equation. I know of no other major structure in this country where the roof snow must be shoveled to prevent a collapse. That this is requirement was included as part of the design is not sound engineering. It would be like requiring an owner of a building in south Florida to put bags of salt on the roof during a hurricane so that the roof wouldn't blow away. There are roofs that were designed before drifting was included in the code where shoveling may be necessary but the owner was not told up front that this would be necessary and the owner didn't agreed to accept the responsibility for this and the liability that would result if they didn't shovel.

The design concept was bad and the owner agreeing to accept this was also a bad decision on their part since they were putting some else's money (the tax payers) at risk.

 

[JRGse]

a2mfk - "....But there is also something special about Lambeau in December or better January!"


I’ll second That!!!!

But there is one thing that I have not read in any of the posts. I saw an interview of someone connected with the snow removal. During the interview he stated that they where using water to remove the snow from the roof.

Using water to melt/remove snow from a roof is something you just don’t due!!

The water is absorbed into the snow creating a slush that is heavier than the snow on the roof. There is a good possibility that this may have contributed to the roof collapse.

 

[JedClampett]

For argument's sake, as far as a structure requiring maintenance (snow removal) to follow its design assumptions, is that different from the use of hurricane shutters in Florida?

 

[a2mfk]

JRG-
We'll see tonight just how special Minneapolis in late December is, guess its been 30 years. I now actually have to root for the Vikes vs Bears, which will be hard for me as a Cheeshead.

I think the articles have said they get up there and use hot water from hoses, not something I have ever tried, and maybe on a sloping teflon-coated roof surface like the dome it slides off in most instances (maybe they forgot to use cooking spray first, I hate it when i do that). Also there is a layer of fabric just below the roof surface where they circulate hot air. Who knows, all sounds way too complicated of a system vs a hard roof designed for the proper snow loads. There is a reason why ski lodges have 12:12 metal roofs, that always works! (I know, ya can't do that for a football stadium.)

But you could see how this method, if it does not get the snow melted and off the roof right away could really "snowball" itself into a bad place. Like others have said above, the roof could sag in some areas, ponding would occur, it would sag more, and so on...

Not a bad point Jed about hurricane shutters, situations are a little different. We often have several days to prepare for a hurricane, if you thought ahead and bought your plywood or have roll-down shudders (most beachfront condos these days in Florida have roll downs or horizontal slide metal shudders.) Few houses outside a few blocks of the coast have these systems because they are so expensive. New codes require them or impact resistant glass if you are in a windborne debris region... But there is a lot of Florida not in that region!

But once a blizzard is dumping you'd need to get up there right away, and that sounds miserable and dangerous, and that is if you can mobilize enough workers in time. Both economic decisions at the end of the day, maybe poor ones in the long term.... How long has bullet proof glass been around? We could build all of our houses out of CMU or concrete with projectile glass or shudders, but, money money money..

People want the cheapest and biggest house they can get with fancy finishes, not a whole lot enters their minds regarding structures and windows and roofs. So slapping up some plywood on your house very 10 years or so isn't such a bad option to many. And maybe repairing a dome once in a while to them wasn't so bad before, but having two games moved to other locations and paying UM for all of that snow removal and whatever else to get that stadium ready, that is costing them a lot.

I'd prefer the ounce of prevention method myself...

 

[anchorengineer]

A bad design is in the eye of the beholder. The owner hired someone to create a program which is based on what they can afford. I buy a car that has a good track record of reliability. I would rather pay more up front than deal with repairs later. If I could not afford the car I chose, what are my alternatives? I would have to buy a more economical car because I still need a car. That said, a 5 series BMW has a terrible track record of reliability. Sometimes you don't even get what you pay for...but it does look good!

Clarke Engineering Services, PC
Construction Consulting & Anchor Testing

http://www.anchorengineer.com

 

[HSIII]

a2...

go Pats

 

[NITTANYRAY]

Anchorengineer,
Would you buy a Yugo?
Would you allow one of your kids to drive it across the country alone?
The owner has to consider more than cost when building a large public venue
What would have happened if the owner of Candlestick Park had made cost saving decisions about seismic design?
I am not aware of any other place in this country where snow loads can be ignored by simply stating that the snow will be shoveled off if it gets too deep
They must have received some type of variance and politics was probably involved

 

[anchorengineer]

NITTANYRAY
I used to drive a 1978 Mercury Zephyr. When you hit the brakes in the snow, the wheels would lock up and you would skid like on skis. I used to practice spinning the car out in my church parking lot so I could learn how to drive it and survive. I learned how to adjust to what I had. My sister used to drive a Chevy Spectrum which was not much better than a Yugo. My parents grew up farmers and immigrated to this country. They did the best they could with the skills they were taught. Have you ever struggled financially? Sometimes what you can afford determines what you choose. Was what happened to the Metrodome really a life safety issue? This was not the first time something happened during a severe storm. The dome had collapsed or deflated a few times from what I've read. The owners chose to go with the inflatable roof and deal with the maintenance later. Did you research the entire system of the dome? Do you really think the snow loads were ignored? There were many things that were in place to deal with heavy snow. Do you think all of the money spent to repair the levies after Katrina will really prevent a catastrophe from happening again if another Katrina rolls through? Is every building in NYC that doesn't meet the most recent seismic code going to be demolished because it is unsafe from a 1 in 100 million chance we have a catastrophic seismic event? Some buildings have been around for 200 years. It's not practical to make all of the changes at once. It would bankrupt the city. They are making changes as they go along and will deal with whatever the good lord sends their way. NYC DoB knows about these buildings. Why aren't they shutting the city down? Why do people bother to live in California? You know large earthquakes will hit there. You sound like a young guy that has great ideals which you should never give up. But as you live you will learn. If you keep doing what you've always done you'll get what you've always gotten.
I wish you well.

Clarke Engineering Services, PC
Construction Consulting & Anchor Testing

http://www.anchorengineer.com

 

[hawkaz]

In watching the game last night, they showed more footage of the stadium in its current state. It looks like the tension wires have kept the fabric well above the ground. I didn't see any shoring, but that doesn't mean it's not there.

Was the fabric designed to give way under a certain load point as a safety mechanism?

Perhaps this is a similar concept as a dogbone connection in moment frames for high seismic. During an event, the joint is designed to yield with life-safety in mind, but afterwards, significant repair work will be necessary to make buildings functional again.

 

[a2mfk]

anchor- you make some good points, but its a bit apples and oranges to me. I say this in all due respect to people who come from humble, poor farmers, as both my parents did too. And from the son of a father who seemed to love buying crappy big cars in the 70s and 80s.

But NFL owners are not normal people with normal problems that are struggling financially. Most NFL owners are already billionaires who buy a team "for fun" to stroke their egos and maybe turn a profit.

The owners clearly have shown what they care most about- a last ditch attempt at a Superbowl run. And in his own way, Favre got the Packers one last time last night by losing and putting the death nail in their playoff hopes... Have a nice life in Mississippi playing football in your wranglers you $$*@#$#*$... Yep, I am a bitter Cheesehead.

FAVRE CONTRACT INFO: 8/18/2010: Signed a one-year, $16 million contract.

Dome Roof:
But while air supported roofs are cheap and fast to build, they are expensive to operate and maintain, and they don't last very long. When Birdair Structures, (these were invented by Walter Bird in 1946) the builder of the dome, inspected it last spring they noted:

The membrane was weathering as anticipated and had exceeded its service life of 20 years; it recommended planning for replacement of the roof fabric, and noted that planning and implementation would take an additional five years and cost $12-$15 million.

 

[concretemasonry]

The question of replacing the entire stadium has put it on the "unsure" bubble for about 5 or 6 years. Because of this the the $15,000,000 replacement of the fabric was deferred. The deflation is not like a collapse because it is slower and not really a life-safety issue even with a full capacity crowd inside that could still be evacuated fast enough. When this collapse was first noticed, there was still time during the middle of the night, they still had time to get someone to come in and turn on the video cameras before the deflation to record the failure process from the interior.

The excess snow removal does use warm water to minimize the damaging use of shovels, but with the slope of the roof and the very smooth warm Teflon surface, the snow slides off and the water flows into the drains.

Due to the collection of ice and snow from a new storm when the dome surface was inverted, it was necessary to shoot a panel with a shotgun to drain it and maintain symmetry. Two other panels are scheduled to be shot in the next few days. I suspect the older panels (not all panels are the same age) will be replaced instead of a new entire fabric replacement because it is possible it will be torn down or be replaced/modified because two of the three major sports teams have moved out and are in their own new stadiums, so the dome will be left with the Vikings as the only major team. There is also a demand for the facility other events, like the high school football championship series, NCMA basketball, tractor pulls and use by other teams for practice and even "squirt" football games, soccer tournaments and tournaments.

The interesting situation will be the question of total replacement and the location if there is a replacement. A unique engineered modification, addition and total remodeling is also possible because of the location, availability of transportation and established habits. After the return to outside football in the winter, the public/fan requirements for a permanent dome may have weakened.

It is a good opportunity for creative engineering and design.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[JedClampett]

Are fabric domes in season in Minnesota?

 

[concretemasonry]

Jed -

Domes are generally not in season, except when shooting them is approved by an engineer for a short term construction/maintenance project. Cities here even hire professional shooters to legally "poach" troublesome deer outside the normal season or where there is no season.

The shooting is a safety and economic decision that must be controlled by a professional recommendation. Since a shotgun slug was used to shoot the dome, I imagine the police would also have to approve it because of the distance a slug can carry. Obviously, pellets would not be controlled enough when dealing with adjacent panels that could be subject to zipper tears, since the deflated tension may be higher than the inflated condition.

Dick



Engineer and international traveler interested in construction techniques, problems and proper design.

 

[mtu1972]

Although I presently live in Wisconsin, I will never be Cheesehead.

I have also temporarilly been a Ranger (Hibbing MN) and don't remember snow loads being all that heavy 30+/- years ago. My recollection is that we only used 30 psf roof snow loads on the Iron Range. Although I never designed anything in the Twin Cities, I see the present Code is as stated above. But it was the late '70's or early '80's when one really bad winter caused the snow loads to be seriously reconsidered.

I am and always will be a Yooper, but have also been a troll (lived below the bridge), and used to see Lions and Piston games in the Pontiac Silverdome. My recollection is that it sold for pennies on the dollar (checked and it was $583,000 in 2009 vs its $55.7 million ost in 1975). The Lions may have had a vested interest in it but I don't think they owned it. Part of its demise was that it lacked the corporate luxury boxes that are in presently in vogue.

I suspect that will also be part of the push behind replacing the Metrodome. This failure will probably help expedite that.

gjc

 

[dhengr]

Jed:
What do you mean “domes in season”? Do we really want that darn thing getting pregnant? Although, it did always kinda look that way in its inflated condition.

 

[a2mfk]

I love the symbolism of shooting at the dome roof... "Hey der, dats a lotta snow up der on the dome eh? We may hafta putter down... Maaa, get my gun."

So last night I saw a scroll on ESPN saying the Vikes lease is up in 2011, and the owner favors a open air stadium. There is about 200 million reasons why...

So we already have frozen tundra in Lambeau, let the brainstorming begin for the new field's nickname.