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Temporary Stage Collapse at Indiana State Fair

Temporary Stage Collapse at Indiana State Fair

RE: Temporary Stage Collapse at Indiana State Fair

It probably depends on the jurisdiction.  They should be designed for full wind load just like any other structure and the work should be inspected.   

BA

RE: Temporary Stage Collapse at Indiana State Fair

From the link:

"Accordingly, engineers are designing temporary structures that are strong enough to survive a once-a-century hurricane when in fact they will be used for only a short period - sometimes just a day or two - and would never be used to shelter people during a strong storm. The most these structures are likely to face is a thunderstorm, but the building codes call for designing for hurricanes, which drives up costs unnecessarily without increasing safety."

I disagree, and agree with BA.

These stages for mass popular events have the same useage as a stadium and the same consequences of failure, so they should be designed to the same standards as a permanent stadium.  The fact that they are moved around between uses is surely grounds for additional caution, not reduced loading.

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
 

RE: Temporary Stage Collapse at Indiana State Fair

MM10...BAretired is exactly right. If the stage in Indianapolis had been designed for the code winds (90mph) the 60 to 70 mph gusts as reported would not have been a factor.  Couple that with adequate inspection and you have 5 people still alive rather that a large group of grieving family members.  Sad that such is allowed to happen.

RE: Temporary Stage Collapse at Indiana State Fair

I was also wondering if there should not be a strong requirement to be equipped with an anemometer, to know the exact wind speed, as you have on the top of tower cranes.  

RE: Temporary Stage Collapse at Indiana State Fair

Marksen - that is a good article that provides an overall discussion of the issue.  They also refer to ASCE 37 which I was going to mention.

For short term duration wind loads, a smaller (statistically speaking) wind load might apply.  However, ASCE 37 uses a time duration of the structure to determine the wind load reduction from the standard 90 mph.  

For the case of a traveling stage rigging, what is the time duration?  I wouldn't necessarily say it was just the 3 days or 1 week that the concert was occurring.  But as it moves around the country, it is constantly exposed to the wind and perhaps has the same statistical exposure as a 10 month structure, or a permanent one.

 

RE: Temporary Stage Collapse at Indiana State Fair

"But as it moves around the country"

In that statement is the problem.  Different juristictions, different requirements, BUT FOR THE SAME STRUCTURE.  This is not a normal situation necessitating professional consultation, not some backyard podunk musician's trainee.

I apologize for my french...

Mike McCann
MMC Engineering

 

RE: Temporary Stage Collapse at Indiana State Fair

The requirements depend highly on the local jurisdiction. I know some colleagues who specialize in stage work engineering, but there are surely many temporary structures out there that haven't been engineered, reviewed or inspected.

As a side note, from a public safety point of view, I would agree with BA, Ron and others and advocate that temporary systems should be designed for the same magnitude of loads as buildings. Although many temporary structure designs have the disclaimer that they must be taken down before adverse weather conditions occur, many irresponsible contractors disregard the advice. Therefore, the structures are still subjected to the same loading risk/probability at any instance of time and should be designed as such (without regard to how long the structure is used).

Structural Design Engineer
New York, NY

RE: Temporary Stage Collapse at Indiana State Fair

Agree with others that temporary structures of this nature should be designed, constructed, and inspected to the same strength standard as permanent structures.  Provisions requiring partial or complete disassembly before the high winds hit are ridiculously impractical and unenforceable.   

RE: Temporary Stage Collapse at Indiana State Fair

... and then is when the matter becomes interesting from an engineering viewpoint, since such opinions suppose a direct hit at the line of flotation of what is assumed as "acceptable" risk, as related to the temporary nature of the works and lower likelihood of the extreme event being met.

Certainly some simple importance factor changing how to could signify a safer design through other rules. But for temporary what we see are waivers, exceptions, more than anything. Philosophically, it looks as if construction wants to retain not only gains from risky business, but a reputation of still being so through lamentable particular cases like the one causing these comments.

RE: Temporary Stage Collapse at Indiana State Fair

Quote (hokie66):

Agree with others that temporary structures of this nature should be designed, constructed, and inspected to the same strength standard as permanent structures.  Provisions requiring partial or complete disassembly before the high winds hit are ridiculously impractical and unenforceable.   

Tower cranes are temporary structures with regulations that require putting them into free slew under strong winds. And it seems practical and enforceable.

Perhaps stronger regulations should be decided for temporary structures which involve the presence of the general public, and even stronger regulations if this general public is a crowd with hundreds of people of more.

Mr Gorlin's comparison with umbrellas or even market tents in http://www.structuremag.org/article.aspx?articleID=833 is a bit hard to swallow because their weight is much smaller than that of the music stage we are talking about and they cannot harm so many people at the same time.

It seems impossible to have one single regulation that would encompass all temporary structures.

RE: Temporary Stage Collapse at Indiana State Fair

Tower cranes are allowed to freely slew whenever unattended.  An entirely different thing than dismantling a structure or parts thereof with limited time after a severe storm warning is issued.

RE: Temporary Stage Collapse at Indiana State Fair

In a previous company we did a lot of design work for stages, generally we designed in accordance with The IStructE "Temporary demountable structures. Guidance on procurement, design and use"

In the document it stipulates a minimumn wind speed for which a temporary structure should be designed based upon it's location, time of year it will be in place and length of time it will be in place.

A management regieme was to be in place with Anemometers measuring wind speeds (gusts not average). At certain wind speeds ie. 60% and 80% of max design wind speed (whether this is as specified above or the maximum the weakest member can accept) the following would be carried out.
At 60% staff whould be put on alert that action may be required.
At 80% with an increasing trend, cladding would be removed and the site would be secured against access by the public within specified zones (ie areas around the structure into which it may collapse).

 

RE: Temporary Stage Collapse at Indiana State Fair

I should note this is in the UK not the US

RE: Temporary Stage Collapse at Indiana State Fair

In true fair/carnival carney fashion it was a game of chance.

Sometimes we play the odds...and don't win.

 

RE: Temporary Stage Collapse at Indiana State Fair

(OP)
I think that it may be acceptable to design temporary structures around masses of people for less than full design wind only if its made very clear that it has been done so.  I bet that the fair officials weren't made aware that the stages were only good for a limited storm.

RE: Temporary Stage Collapse at Indiana State Fair

I disagree with others that support designing these for full wind loads.

Even a reduction from 90mph to 70mph would result in only 60% of the pressure and huge cost savings.

Hurricanes dont form in minutes, there are usually quite a few hours of warning for which the site can be evacuated.

I think that there is definately a case for nationalised standards that can be waved in front of the local official.  

RE: Temporary Stage Collapse at Indiana State Fair

I kinda, sorta agree with the concept of designing for reduced winds based on statistical models, evacuation procedures and disassembly requirements. But in this case, the reports say that the structure failed at 60 mph. That means it wasn't designed for 60 mph, but a wind load even smaller. This wasn't a hurricane moving in from the coast, taking days to develop, it was a midwest thunderstorm that happened suddenly. The crowd either felt safe under the shelter or had no place safer to go.
If it was correctly assembled (a big if), I suspect that the forensic study will show it was safely designed for some wind of a magnitude of 45 mph.

RE: Temporary Stage Collapse at Indiana State Fair

I'm just arm-chairing it from a grainy video of course but it doesn't look to me like the stage was constructed with an expectation of lateral load.

 

RE: Temporary Stage Collapse at Indiana State Fair

Im not sure, but in another post there were some details of the structure, and how if its to be used outside, guy wires need to be installed. Were there guy wires installed? I hope not for the engineers insurance policy sake.  

RE: Temporary Stage Collapse at Indiana State Fair

The wind front was five or ten miles ahead of the storm. The rain front, in falling, drives a column of air down on the ground where it spreads out sideways as a big wind front along the ground. People were mapping the the storm on radar, but that shows the rain, not the wind. They were waiting for the thunder storm to to get close before evacuating.

Michael.
Timing has a lot to do with the outcome of a rain dance.

RE: Temporary Stage Collapse at Indiana State Fair

Quote (hokie66):

Tower cranes are allowed to freely slew whenever unattended.  An entirely different thing than dismantling a structure or parts thereof with limited time after a severe storm warning is issued.

When a tower crane is in operation while the wind speed is low, followed by a rise of wind speed, the crane's anemometer rings an alarms which tells the crane operator that he must cease working: unload the load, rewind the hook and the trolley, put the crane in free slew mode and climb down. I guess it takes a few minutes to do all this. And we don't hear about wind-related tower crane accidents so often.

If you have a team trained for this, it doesn't need to take much time to lower the roof. These stages are similar with sailing ships. You need a crew to promptly reduce sails when the storm is coming.

You could also have a regulation to lower the roof of a temporary stage whenever unattended.

 

RE: Temporary Stage Collapse at Indiana State Fair

More armchair quarterbacking follows:

- It didn't look to me like the structure had much in the way of lateral stability.

- I'm with Jed in that for it to fail at 60 mph then it had a real "design" capacity of 40 mph or less. This is unacceptable to me.

- The reality is that the people what erect things like this play the odds and almost never get caught. (See the collapse of the Dallas Cowboy practice facility.)

- It takes a large mistake to overcome all the load factors and all the material safety factors to actually produce a failure.

- Tower cranes, by and large, are run by trained professionals. I'm not sure the same can be said about fair staging and rigging.
 
    

RE: Temporary Stage Collapse at Indiana State Fair

I wouldn't argue too much about the appropriate wind speed for design of these things.  Maybe it can be less than for permanent structures.  Whatever wind speed is selected, I would bet the bar that in this case, something was omitted from the construction.

To rely on removing cladding or lowering a roof as a thunderstorm approaches seems ridiculous to me.  Anemometer or not, weather prediction is just not that good.  Who is going to be the rigger risking his own life and limb to save the structure?

RE: Temporary Stage Collapse at Indiana State Fair

You wonder about the loss of knowledge that occurs over time with structures like these.  The original designer/manufacturer perhaps had a checklist and user-manual on how to erect and maintain the temp. structure as well as a wind capacity/warning aspect.

As the temp structure is used over time, personnel change, the manual is lost, the structure is sold to someone else who doesn't get or doesn't read the manual, etc.  At the end of the day did the individuals who erected the structure have the knoweldge and authority to close down the program when the weather kicked up....or was anyone even thinking about the danger?

 

RE: Temporary Stage Collapse at Indiana State Fair

Exactly my point JAE...

Mike McCann
MMC Engineering

 

RE: Temporary Stage Collapse at Indiana State Fair

I agree that the structure should have been capable of withstanding more than it has, I just disagree with the gut reaction of some that it should be designed for the same as a building.

Some structures would be impossible to build if they had to withstand the full wind load at every instant during construction. There has to be some rationality.

There are no 100% guarantees only statistic improbabilities of failure. There is nothing to stop two 1 in 1000 year events happening in the one week, its just very(to the power of fifty)unlikely

RE: Temporary Stage Collapse at Indiana State Fair

Construction of the subject structure was alleged to be complete.
 

Mike Halloran
Pembroke Pines, FL, USA

RE: Temporary Stage Collapse at Indiana State Fair

perhaps a PE should be hired to inspect, and bless it once erected. At least then it would have some professional who looks at it, not just the county fair chairman walking by it chewing his hot dog.  

RE: Temporary Stage Collapse at Indiana State Fair

@csd72, Obviously it would be impossible to provide full wind stability during construction, but I disagree on the the design of the finished structure. I believe they should be more stringent because of the material losses from wear and tear due to the constant construct/tear-down sequences, and the loss of original knowledge/memories. I also suspect that their risk of design wind is higher per day of use, the normal building stands 365 days per year, these structures for much less, but mostly in the high risk season.

The Willow Island Cooling Tower Disaster is a good example of lost knowledge/memory. Research-Cottrell used a jump form system where the scaffolding, forming and "cranes" for pulling buckets of concrete up a sloped wire from ground. The system had been used many times, worn HS bolts had been replaced with black bolts, They were moving the forms up before the concrete was sufficiently set, and they were running the bucket up at much higher than design speeds leading to much bigger impacts. When the system collapsed, fifty one men died.

Wiki's report is a pretty good condensation of the official one.

http://en.wikipedia.org/wiki/Willow_Island_disaster

 

Michael.
Timing has a lot to do with the outcome of a rain dance.

RE: Temporary Stage Collapse at Indiana State Fair

Re Willow Island,
OSHA's fine was settled for $1700 per dead man.
No wonder things don't change.
 

Mike Halloran
Pembroke Pines, FL, USA

RE: Temporary Stage Collapse at Indiana State Fair

I am not trying to pass myself as a structural engineer, nor do I have any detailed knowledege as to the what happened in Indiana. I have been involved in outdoor events on a volunteer basis for about 20 years and offer some of what I have learned from this. Take it for what it's worth.

For the most part, the people who set up, babysit and tear down the stages and so forth consider what they do to be as important as what you and I do, are generally very safety-oriented and consider themselves as much a professional as you or I.

The equipment is generally shop-built and of good quality, although I don't know what standards it may be designed and built to. Perforce, portability and ease of set-up / teardown are major condsiderations in the design of the equipment.

Jurisdictional issues have been mentioned by several, and I can tell you that it gets more difficult with each passing year to throw an outdoor festival, what with the Fire Marshall, Health Department, and who knows what all enforcing their piecemeal regulations. In my area, the authorities generally try to enforce, to the extent they can, building codes for temporary event structures such as tents. As an example, several years ago we had to start placing lighted exit signs in each tent. Adding another layer of inspection such as a PE would no doubt help, but no guarantees, after all permanent, Code designed structures fail due to weather and other causes with some regularity.

Deciding whether to evacute an event due to weather or other reasons is not easy. There is a non-negligable possibility of causing harm during an uneeded evacuation that has to be weighed against the potential harm from not evacuating. Remember, we are talking about the general public here. This is completely aside from the business considerations. Due to the legal climate the risk of getting it wrong either way is not attractive.

A few years ago, an event I was involved with had what was generally considered, by the people running the event and making the decisions, a fast moving but not particularily severe thunderstorm collapse directly above the event grounds, creating a microburst. Some severe damage and injury did occur. This in spite of opinions of local weather people and so forth, who the organizers were in communication with, that this storm was not especially threatening. The risks of evacuating were judged PRIOR TO, and rightly I believe, to be worse than the risks of staying put.

It can be a risky business, you do the best you can.

Regards,

Mike

RE: Temporary Stage Collapse at Indiana State Fair

Coming from someone who had dug a lot of ditches I can tell you that the speed and choas with which these events occur will never tolerate a team of white collar inspectors signing off on every nut and bolt. This is a traveling circus. The establishment of more rules and "safety" nets to prevent accidents like this will only lead to more "corner cutting" by those who are told "get that damn thing up right now or find a new job".

I know that will make some blood boil on this site in the name of life safety, but I'm just telling you how it is in the field boys. If I haven't had a job for 6 months and I have 3 kids to feed, I will choose job over the 5% chance of that thing falling down any day of the week.

And finally, why leave the decision to call the event up to a person, who the last time I checked is persuaded by a million things. I simple device that measures wind speed, connected to an alarm, that could be only heard by even planners, so as to not cause chaos, would indicate guess what fellas....get everyone out the shows is over. That way when everyone comes crying about how much $ they lost etc., all the event officials do is point to the machine and say, "This is why the show was called".

 

RE: Temporary Stage Collapse at Indiana State Fair

Mike H:

If these structures had properly sized deadmen, they wouldn't have dead men.

Mike McCann
MMC Engineering

 

RE: Temporary Stage Collapse at Indiana State Fair

From the Toronto Globe and Mail, "Indiana's decision to essentially police itself as it investigates a fatal stage collapse at the state fair is raising questions about how objective the probe will be.

Workplace safety agencies, state police and fair officials are looking into Saturday's collapse that killed five people and injured dozens. But the lone outside agency brought in so far is an engineering firm hired by the Indiana State Fair Commission.
More related to this story

    At least three killed as storm wreaks havoc at Belgian music festival
    Five killed, dozens injured by stage collapse at Indiana State Fair
    How the Ottawa Bluesfest stage came down – and why it could happen again

Kentucky attorney Jerry Miniard, who represents an injured girl, says the state is essentially investigating itself.

An expert says that could be a conflict of interest. Judy Nadler of the Markkula Center for Applied Ethics at Santa Clara University says it might be better to appoint a regulator from another state to investigate."

Dik

RE: Temporary Stage Collapse at Indiana State Fair

msquared48, at one of the events I worked, years ago, they had the stage top tied to several Jersey barrricades, don't know for sure, but probbly one at each corner. You'd think that would be deadman enough.

A gust lifted one of the barricades enough for it to come back down on a guy's shoe, fortunately just missing his foot.

Regards,

Mike

RE: Temporary Stage Collapse at Indiana State Fair

SnTMan, sorry, but you just don't know how ridiculous that sounds.

The whole emphasis with these things, including the ones which have collapsed, seems to be support of the lighting and sound equipment.  Not much thought to lateral stability or uplift.  The typical guywire anchorage details shown by the outfit which designed the Indiana structure showed the type of screw in anchors used to stop house trailers from blowing away.   

RE: Temporary Stage Collapse at Indiana State Fair

It's noteworthy that about a year ago, a temporary tower being used by a Notre Dame football videographer collapsed in a windstorm, killing the worker. This happened in South Bend, Indiana. It seems that Indiana may have an enforcement problem.

RE: Temporary Stage Collapse at Indiana State Fair

(OP)
I'm not sure that the building dept has anything to do with the use of scissor lifts like the one that toppled at Notre Dame.  For what it's worth though, Indiana is one of two states in the US that doesn't formally have special inspections in the code.  Not that special inspections could have been applied here, nor are they correctly enforced elsewhere the midwest....that's another thread altogether.

RE: Temporary Stage Collapse at Indiana State Fair

so what state level official or department is typically responsible for regulating these temporary structures? i'm reading now that neither the fire marshal nor the city building department had jurisdiction since it is on state land. perhaps the department of agriculture or  the department of labor? and do they employ any structural engineers or only amusement ride inspectors? i'm beginning to doubt that this could have been avoided under the current system since no one with any structural knowledge is included in the process once the original structural package is fabricated and sold. again i'm just arm chairing and give full deference to those with first hand knowledge.

RE: Temporary Stage Collapse at Indiana State Fair

hokie66, just telling you what I saw..

RE: Temporary Stage Collapse at Indiana State Fair

You can have a PE look at these structures and do inspections in the period they build them, our firm has done it, the city and there inspector out there to do there's as well.  It's no different than any other job.

I am thinking that this is not a design issue but a construction issue, just from looking at some of the pictures.  But thats my WAG

RE: Temporary Stage Collapse at Indiana State Fair

Jed,

This is actually a quite common design philosophy on temporary fabric structures.  

RE: Temporary Stage Collapse at Indiana State Fair

According to the story, the tearout panel _did_ release at 20 mph earlier in the week, and was then reinstalled, apparently in a way that prevented it from releasing until the wind reached 70-ish mph.  Big oops there.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: Temporary Stage Collapse at Indiana State Fair

It might be common, but it's still scary for two reasons:
1) How do you design something, especially a fabric, to fail at a certain load? It seems easy, but in practice, it's pretty hard.
2) It would be tempting to the staff to say, "...hey that tarp keep blowing off its mounting.  People are getting rained on. Someone go up there and wire it up better."
 

RE: Temporary Stage Collapse at Indiana State Fair

Considering the stage top is intended for outdoor events, a panel blowing out at 20 MPH is going enough of a headache to guarantee it will get wired in securely. Too low a design windspeed unless the top is designed for say 30 MPH max.

Regards,

Mike

  

RE: Temporary Stage Collapse at Indiana State Fair

I think this issue boils down to the fact that the building industry want's to avoid using a licensed SE in every way possible..and then when something fails everyone is surprised.  I think a licensed SE should be obtained any time a large temporary structure with potential to kill a lot of people is erected.  I'm willing to bet that any of the struggling SE's in the area would have been happy to review the fair's large temporary structures for less than $1500....and now the state is going to pay out millions.  Its ludicrous.

I think these structures should be designed for the standard code level loads.  Nobody has a good handle on the probabilities and life safety risk, therefore any loading reductions are merely a guess.

This is a code issue, and the good ol boy engineering mentality came back to bite Indiana on this one.   

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