The popular winter-time ice arena in Bellevue averted a near tragedy yesterday, when employees and firefighters quickly rescued 10 people trapped under the failed roof tent. The snow load exceeded the capacity of the roof structure, and the whole thing failed in the blink of an eye. While a fabric tent collapsing may not sound super dangerous, it’s easy to underestimate the tonnage of snow involved, the hazard caused by the metal support stuctures, and the electrical hazzard resulting from the lights and sound system plunging to the ice.
Fortuanatly, there were only minor injuries. I’m sure there we be an analysis to determine whether the tent supplier included proper instructions for snow clearing or not, and whether the users paid attention to the growing hazard. It seems obvious, at least in hindsight, that there should be some engineering which gives the user an idea of when to clean the tent roof or clear out if the tent was really designed for winter use.
I’m really glad there were not any serious injuries.
This is a great reminder about the hazards caused by overburdened roofs. Back in engineering school, we were given a great deal of education about how roof loads can quickly accelerate in bad weather due to accumulations of snow and ice, frozen drainage systems, and general “ponding” of water. This “ponding” phenomena remains one of the most common and most dangerous roof failure modes. It occurs on flat or nearly flat roofs, when obstructions like leaves or ice reduce the normal drain paths for water. The weight of the accumulated water on the roof will then “deflect” the structure, causing support timbers to bow under the weight, and creating more opportunity for ponding. The more the pond grows, the more the boards deflect, and the more water the roof will contain. Many people have seen this mechanism where they have tried to string a tarp up over a picnic table while camping, only to see the whole thing collect water. “Ponding” represents an engineering instability, in that the more it occurs, the more likely it is to get worse. The only protection is the keep the drains open, inspect the roofs frequently, and be extremely aware of how things are holding up when there is any kind of load on the roof. So, if we get more snow, and when the inevitable rain comes, be very aware of the conditions of your low-pitch roofs. Even if conditions are too dangerous for you to clear your roof, you can still make sure loved ones are not sleeping or spending large amounts of time under anything suspect.
If you are concerned that your roof is not holding up, and you need advice, the city building department can give you some recommendations.
Here is the story about the Bellevue Ice Rink roof tent collapse
It only takes about of foot of compacted cascade snow on top of you to pin you down.
If you work for Kenworth, this is a good thing to know.
I used to live right next to the Bellevue park, and I always thought it was a problem waiting to happen. Even in the rain, they wouldn’t push up the tarp to get rid of the puddles. The sad part is, instead of simply learning from the experience, they are probably going to shut the whole thing down for “safety concerns”.
In Renton concerns, it’s been two weeks since I’ve had garbage pickup. Do you know of WM is going to make some back-to-back runs to get rid of the backlog? My garage is starting to look like a dump…
Hi Joikm-
Very interesting info about the skating rink tent. So they would actually have to knock puddles off it?… that is ponding for sure.
Your question on the garbage is a good one. After seeing your comment I decided there would be general interest in this topic, so I just posted a blog about it.
Thanks!
Thanks Randy!
– Erick
I would not be surprised if rather than just shutting the rink down, some extra provisions are added to the agreement with the vendor who runs the rink. The story pointed out that it is privately run — part of the Magic Season — and that private vendor has to meet restrictions placed on them by the city. Group Health was recently added as a sponsor, and it would be interesting to know if they have a long-term sponsorship agreement or not. If so, the vendor would be even more interested in meeting safety requirements.
This is a good example of how heavy snow can be. There was a building in Marysville that had a roof collapse, and I’ve heard of a few homes with flat roofs that have started sagging. Rain on tents tends to just cause excess stretching in the canopy material… the snow places all that extra weight on a support structure that’s meant to only hold up the vinyl roof.
I hope that is the case – it’s a great service, and it really makes the Bellevue park fun in winter. Even if you don’t stake, it’s great to hear the music and see the cheer as you walk around the park.
My concern is that if they get hit with a lawsuit, the costs of making sure every i is dotted by lawyers would cost more then it’s worth to keep it open. Hopefully they have good insurance.
You can bet that the city is well-covered by hold harmless clauses and insurance held by the vendor operating the rink. If I remember correctly, Bellevue has its own in-house attorneys office, so there’s not really an issue on the city’s end with legal fees. It’s part of the budget.
I was thinking about the rink operator, as they are the one who wouldn’t come back next year, but I am sure the city made sure they had insurance.
My daughter was six
when she was crushed under the snow at the ice rink. It kills me to see people post that only minor injuries occurred. That’s what ‘they’ want you to think. They don’t talk about the massive head injuries she received or the fact that we deal with this on a daily basis or all the therapy she has had to under go. Or the fact that she is now terrified of everything. Or her future dreams of being a competitive ice skater went out the door the night she was pinned face down on the ice with close to three hundred pounds on her back. We are so lucky to have our daughter, but no one seems to think of what happens mentally to these people when they live through some thing tragic. Our whole family has suffered because of this night that was suppose to be a happy memory. Instead it brings back so much anguish and anxiety. All of these people played a very critical role in my daughters life and it’s very upsetting to hear in testimonies that the workers wanted to close early that horrific evening because the snow had piled up so much and they couldn’t knock it down. But were told NO. They had to make a profit. Seriously, at what expense do you go through to make a profit? The value of a life that has no been forever changed. Hope it was worth it for them.