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Metro Dome collaspe

Metro Dome collaspe

Metro Dome collaspe

(OP)
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.  

RE: Metro Dome collaspe

Maybe they should repair it with a Velcro strip so it will re-tear in a predictable manner.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Metro Dome collaspe

The roof deflated after there was a fabric failure the allowed the deflation. The snow removal was stopped because of safety and weather conditions a few hours before the failure. Actual snowfall, which is misleading was somewhat more and the changing wind and drifting caused localized loading.

The roof structure is supposedly stronger when deflated, but does not provide the space between the layers for air and heat circulation. The sagged/failed roof surface and cables still support the lights, speakers, scoreboards and other loads even after the failure. - The question is how fast it can be repaired since the materials are available. Three large cranes (interior and exterior locations will be used for detailed inspection and for lifting the structure to allow remaining snow removal. The practical/economic life of the 30+ year old structure is questionable because of other teams and development, but the infrastructure is in place for something different. It was intended to be a multi-purpose building with some practical use disadvantages now that other new specialized stadiums (baseball and football) are now available.

There were also 3 other air supported structures that collapsed during to 17" to 20" snow and winds. - No injuries and no major property damage.

Dick

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

RE: Metro Dome collaspe

(OP)
According to ASCE 7 Minneapolis has a uniform ground snow load of 50 PSF. ASCE 7 also requires domes to be designed for drift loads. While the cables held the fabric is part of the roof structure and it should have been able to support the drifted snow. Either the fabric was worn out and should have been replaced or it was never designed properly.
The collapse should have never happened. It casts a black-eye on the design profession much like the Kansas City Hyatt collapse. When I hear that this was the fifth time the roof has deflated I can only shake my head. How many warnings do they need. It is fortunate that no one was injured.

It reminds me of an experience I had with some builders and building officials in Gulfport, Miss.
We had designed an elderly housing building for a 140 MPH wind load. The developer complained that the local code only required 120 MPH. The building official agreed saying that the 140 MPH would not take effect until 2006 since they were still using an old code locally. I did some research and found out that Hurricane Camille hit Gulfport in 1969 with winds up to 145 MPH. I explained that it would not be ethical for me to lower the design wind load because public safety was more important than saving a couple thousand dollars. For some reason the locals did not think a hurricane like Camille could happen again.
Had the Church sponsoring the building not run into financial problems the building would have been under construction in 2005.
Knowing what I know about the local attitude about building codes, I was not at all surprised when I saw the damage Katrina did in Gulfport and the surrounding areas.

The apartment building was one of the first new structures built after Katrina and it was built to meet ASCE 7 design criteria with no objection from the developer.

RE: Metro Dome collaspe

I need to disagree about this being a black eye on our community. This was a freak storm and I don't believe people criticize engineers for something like this. The bridge collapse in Minneapolis is a different story.  It came down without warning or an obvious outside stimulus.

Every year a heavy snow storm hits somewhere, causing roofs to collapse. Should we increase snow loading to prevent this- Perhaps, but where do we draw the line. We could increase the snow load in Minneapolis to 100 psf, but is that realistic? We base our loading on statistics and a rational approach. There will always be anomalies.

We don't design for tornado level wind gusts. We could, but no one could afford to build our buildings anymore. The auto industry could design cars that are 100% safe, but no one could afford to buy one... Whether we like it or not, we need to draw a realistic line somewhere. 50 psf ground snow load in Minneapolis sounds reasonable. If something changes to cause this to be re-evaluated, then it will be done.

By the way, NITTANYRAY, I applaud you for sticking to your guns on the wind speed. As soon as is was deemed inappropriate, it probably should have been addressed in an emergency addendum for that locality rather than waiting for the next code cycle. This is how moment welds were addressed after Northridge.
 

RE: Metro Dome collaspe

Not exactly an exhaustive investigation yet, but this is interesting:

http://www.treehugger.com/files/2010/12/metrodome-roof-failure-symptom-of-larger-failure.php

"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."

Sounds like it comes down to economics at the end of the day, unfortunately, like everything else it seems...

Nittany- I wouldn't say it casts a black eye on the profession unless they do an extensive investigation and determine that it was a design error. Like you said, and so does this article, it looks like it is a maintenance-related failure of the fiberglass roof membrane material. This is a lot different than an original design error. A roof of a building you designed could collapse because the owner reroofed over the secondary scuppers and let leaves clog up the primary drains...

Like in your case study, which is very interesting (I had some unusual experiences in Biloxi post-Katrina with building construction attitudes), sometimes you have to out-fox the owners to keep them or future owners from hurting themselves. Sometimes designing to the letter of code maybe is not as prudent as realizing what that building may eventually be asked to do, regardless of the owner's original intent. Usually they are not wise enough to know that you may have cost them a few extra bucks for the greater good, and you have to fight them, which you wisely did.

When utilizing a material or system that is state of the art, there will be failures along the way, hopefully none that are catastrophic or due to negligence or poor design. There have been monumental dam, bridge, aerospace, and building failures that have advanced the state of the art by leaps and bounds (or made the systems obsolete or proved their lack of functionality).

I wouldn't say fabric roofs themselves are even the problem, I did a little research with the Denver airport roof and only found one failure in a huge snowstorm in 2006. It said there was a small tear in the roof that allowed some snow to fall in. Maybe tensioned fabric roofs are more dependable than those requiring constant internal pressure to support them.

Maybe the savings up front in the dome roof at the Metrodome proves to be worth these "inconveniences" every once-in-a-northern clipper. Knowing so little about how these roof systems work, almost as a layperson it seems that its a bad idea in a heavy snow area...

Also, I have not read if the air pressure is kept constant or do they increase it during snow events to balance out the snow loads?

RE: Metro Dome collaspe

(OP)
Hawkaz,

The average person doesn't know who is at fault when something collapses. All they know is that it collapsed.
The politicians that made the decision to put off the repairs are going to need scape goats and the designers are considered to be low hanging fruit.

When you talk to a layman about the WTC, they want to know why it collapsed. The real question should be how did it stand up so long because it was never designed for the impact of a 737 or a 2000+ degree fire.

People expect buildings to withstand extreme events because so many do that it has become the expected norm. When collapses do occur, they start to raise questions in the minds of the public which is not good for the profession.

Raising the snow load to 100 PSF is not the answer especially since the 17" snow fall is only about 20 PSF +/-
depending on the density of the snow. The winds were less than 90 MPH and the snow was less than 50 PSF and the code requires that drift loads be accounted for. The "freak storm" as you described it, was within the design requirements of the code.

It is possible that it was a maintenance problem, but who ever made the decision to not replace the roof fabric that had exceeded its useful life was just rolling the dice and they came up "snake-eyes".

As far as tornadoes, there are buildings designed for tornadoes. We designed a jail that could withstand a F-3 tornado at no extra cost to the owner. Because of security reasons, jails already have considerably more reinforcing than other buildings. With carefully detailing we were able to build a structure capable of surviving a mid level tornado.

RE: Metro Dome collaspe

Regarding the codes and statistical analysis.  You're correct in that the codes are based on this...and more.  

But ours is a changing environment and we need to evaluate the code through statistics and other tools to see if the loads are, in fact, sound now as they once were.  This works both ways as I'm sure there are certain loads that become obsolete.  

So in effect I do beleive that should an analysis show that Minneapolis or some other large region need a 100 psf snow load then that's what it should be.

Regards,
Qshake
pipe
Eng-Tips Forums:Real Solutions for Real Problems Really Quick.
 

RE: Metro Dome collaspe

I have a hard time understanding how anyone can call this a freak snow storm.  The amount of snow deposited was much less than the snow loads required by code.  So this roof failed at less than code level loading.  This is a major problem.  This is also not the first time it has failed, far from it.  This should be screaming "Bad Design" or more simply bad choice of structure (or lack thereof) for the given environment.  There should not be any requirement for snow removal to keep the roof from collapsing.   

RE: Metro Dome collaspe

The fabric roof is a temporary structure, used well beyond its stated design life, apparently without plan or budget for its eventual INEVITABLE failure/removal/replacement.

That's not an engineering problem.

That's not a code problem.

That's a management problem.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Metro Dome collaspe

Per the Minneapolis news- This was the third worst storm in their recorded history. I'm not there- so I can't speak to it personally and my info (as is most everyone else's) is hearsay and conjecture.

I have always had an issue with calculating density of snow. Anyone from snow country can tell you, there is wet snow and there is dry snow. Dry snow can have a density as low as 6.2 lbs/ft^3, wet snow can get to 31 lbs/ft^3. This can be 50% higher than the code required density calc for a 50 psf area.

I don't know which type of snow this was. If they has 17"-20" of wet snow, they could have been very close to or even exceeded the design snow load. If there was already old, heavy snow on the roof, this would further increase the loading.

I don't know enough about the geometry/slipperiness of the roof and the pockets created by the tension wires, so if we theoretically use flat roof design and ignore drift for these purposes:
Ce=.9, Ct=1 (debatable), I=1.2, pg= 50 psf
Pf=.7x.9x1x1.2x50=38 psf or 15" of wet snow.


Wet snow doesn't accumulate as much as dry snow, so 15" would be a lot- most likely the density was somewhere in between. I wouldn't be so quick to say that the snow load didn't exceed design loads without more info.
 

RE: Metro Dome collaspe

(OP)
I have personally measured fresh fallen wet snow and it weighs about 12 PSF. Over time the snow will consolidate especially if there is a freeze and thaw cycle or rain on snow. The higher densities you mention only occur if the snow has been on the roof for an extended period of time or from the build up of several snows. In a 12" deep cube of snow the bottom half is generally denser than the upper portion due to the weight of snow above. This is why the density of snow as specified in ASCE 7 increases with the ground snow load.
There was probably drifting because of the high winds but the code requires domes to be designed for unbalanced snow loads.

RE: Metro Dome collaspe

There were actually 2 snow events. The first started late Friday was an "Alberta Clipper" followed by cold air and wind), which is a light dry snow. On Saturday morning we had 4-7" of light, dry snow and still had to wait in line to get into a local pancake restaurant for breakfast because there was no travel inconveniences. Flurries continued lightly during the day and then a southern flow of moisture hit the colder air air and snow was the result. From what I understand, the dome roof had excess snow removed by shovels and it is melted by hoses and drained off. This procedure has worked.

The second phase changed the snow moisture content, wind direction and the drifting effects. The actual snow (at the airport) was about 17", but varied widely depending on exposure and measurement  location. At my home in a NE suburb, the accumulation was somewhat less. Southwest of me the amounts were less and southeast of me they were somewhat greater (over 20").

The snow removal was abandoned because of conditions and safety at about 1:00 AM on Sunday and the dome was monitored and a problem was detected about then. At about 5:00 AM, the video cameras were turned on to tape the failure. It was not an immediate failure or an immediate collapse and everyone was gone and there were no fatalities.

Since U.S. codes are generally written for life safety and not absolute, immediate "collapse" (TV term) was not the problem as many codes in some other countries.

The weather situation really was not the 3rd worst, since the second and third previous storms (20") were only several days apart and it only was the 5th worst.

When designing, it is important to separate the immediate collapse (seismic, etc such as the the Albanian earthquakes where about 20,000 died) and the gradual failure that allows evacuation due to the time involved.

Fortunately, the codes allow the engineers to design according the the conditions possible and the failure modes to over-ride the provincial standards.

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

RE: Metro Dome collaspe

We got about 18-20" of snow in about 18 hours, approx. 11:00p FRI. through 6-7:00p SAT., 11DEC10 and had very strong winds from the north, thus lots of serious drifting.  That's not a wimpy storm around here, we were pretty well shut down on SAT. & SUN., airport, transit, and all but the really stupid people who go out and try to get stuck, and then prevent street plowing.  It was the 5th largest snow fall depth and blizzard in recorded weather keeping, largest snow fall ever in DEC.  Concretemasonry, I live in WBL, hide your edress, something at something dot something so we can talk.  I had 2 or 3' deep drifts in my driveway.  Several of the neighboring houses have approx. 4' deep drifts up on the south planes of the roofs.  I weighed several blocks of snow and it came in at about 9#/cf on SUN morning when the snow stopped.

If you saw the video:   at the underside of the roof and then later from above too, you see what is almost a quilted effect in the fabric, from the tension strands.  There is an inner layer of fabric which you see, and a second outer layer of fabric, but they both show some form of this quilting effect from the tension cables.  Thus, you get a fabric panel which is supported on three or four sides by cables, which can deflect down from snow load.  Obviously, you will get drifting on the leeward side of the roof, and drift depth can increase as the fabric and cables settle, the arched shape of the entire roof changes under this loading, almost a ponding effect, but worse than would occur on a stiffer roof structure.  Furthermore, the roof is warm enough so they do melt snow up there, adding to the ponding effect, and I think the video shows both snow and the water.  They would have been warming the building for the game on SUN, adding to this melting action.  Finally, they were up on the roof shoveling and melting snow, with warn water, to try to get it off the roof, when an edge (triangular) panel broke and cause the roof to deflate; then all the snow and water tended to slide to the center and caused a couple of square fabric panels to fail, and dump on the field.  The roof, particularly the cable system, was still basically structurally sound, and intact.  But, at this point individual square fabric panels become the weakest like, and are obviously overloaded.

Now, last night, while they were working to clear the field and get ready for the roof repair, another square fabric panel, near the center of the roof failed, with a large dump of snow near an end zone.  I agree with MikeHalloran, I don't think this is really an engineering or code problem, or the fault of bad engineering.  It's a building maintenance and management problem, they got what they asked for when it was built, and must then learn and understand what is needed to keep the roof functioning under these rare conditions.  We've had a number of other smaller air supported structures fail also.
 

RE: Metro Dome collaspe

As a kid in Wisconsin I remember how crappy a job snow shoveling was, I wouldn't want to be the poor saps up there, doing it on top of a fabric dome supported by air pressure. Whatever you do, DO NOT poke the blade of your shovel in the roof!! Hope they had some good tie off system ;)

Just thankful to live in Florida when I hear your blizzard stories...

 

RE: Metro Dome collaspe

(OP)
Here is another opinion from the Architecture and Design web site:

"The Metrodome was not lovable; it was brutal and ugly and cheap. It was not durable; one sixteenth of an inch of fiberglass is not going to last. It was not particularly flexible, incapable of adapting to the seasons and it certainly wasn't frugal, needing continuous supply of electricity just to stay up.

They will stick on a few patches, re-inflate it and be playing inside again soon. But it will remain an object lesson in how not to build."


They should have never built an inflatable structure in an area with high snow loads. A structure similar to Madison Square garden would have been a better choice.

Part of good design is choosing a structural system that can function in the environment it is placed with only a minimum amount of maintenance required for it to function properly. Value engineering should include the cost of maintaining it. I am sure that what ever they saved buy using this cheap roof has been spent several times over just to pump the air to pressurize the building

RE: Metro Dome collaspe

I'm a huge fan of retractable roof stadiums, especially in northern climates where it is awesome to be outside until November or so... And in really hot climates like down here in Florida, which is why the new Marlins field has that type of roof (and because of severe afternoon thunderstorms all summer).

But there is also something special about Lambeau in December or better January!

RE: Metro Dome collaspe

The Vikings do actually like an outdoor field.

The next game will be moved to the new state of the art University of Minnesota stadium (50,000 capacity) and played outside on national TV Monday night. Because the stadium was winterized/shut down the cost (including snow removal from the field and seats) will be $400,000 to $800,000 plus the cost of erecting additional temporary stands since the sold tickets exceed the university capacity. The activation of the water and sewer system may be a bigger challenge than the snow removal (24"), because there are many students on break that want to get paid for working before Christmas and there are plenty of loaders and other equipment and there is land for snow dumping.

During the inspection, using 3 cranes they discovered some additional weak panels/spots in the roof surface, but the cable structure and ring were apparently satisfactory. The relocation and the scheduled use of the dome will allow more time to install additional panels before tractor pulls and the basketball games start and buy time to decide on a replacement stadium if and when it is necessary.



Dick

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

RE: Metro Dome collaspe

There used to be a code in the UK for farm buildings, for which the snow load depended on the number of hours per week of human occupancy. As if the snow 'knew' what kind of building it was falling on!!!! I see the point of it, but it was the wrong approach to safety.

RE: Metro Dome collaspe

Signs of the youtube age... When something is caught on video now it goes around the world in seconds! Convenient that Fox had their cameras running all night. If TV and video were as crazy during WWII, would FDR have ever been elected? People will forget about this quickly because no one was hurt and there will be a million other things that their brains get inundated with soon enough. And it was a maintenance thing.  

Clarke Engineering Services, PC
Construction Consulting & Anchor Testing
www.anchorengineer.com

RE: Metro Dome collaspe

(OP)
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.

RE: Metro Dome collaspe

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.
 

RE: Metro Dome collaspe

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?

RE: Metro Dome collaspe

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...

RE: Metro Dome collaspe

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
www.anchorengineer.com

RE: Metro Dome collaspe

a2...

go Pats

RE: Metro Dome collaspe

(OP)
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
 

RE: Metro Dome collaspe

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
www.anchorengineer.com

RE: Metro Dome collaspe

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.
 

RE: Metro Dome collaspe

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.

RE: Metro Dome collaspe

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.

RE: Metro Dome collaspe

Are fabric domes in season in Minnesota?

RE: Metro Dome collaspe

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.

RE: Metro Dome collaspe

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
 

RE: Metro Dome collaspe

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.
 

RE: Metro Dome collaspe

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.

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