# And another high school pit cover failure



## gafftapegreenia (May 13, 2014)

Only a small news article at this time. Its hard to tell from the photo, but it looks like the sheet good used was OSB.

Stage collapses during Rockdale County high school concert | www.ajc.com



stage_collapse.jpg


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## headcrab (May 13, 2014)

The broken edge does look like OSB.

If I load a 4x8 sheet (of anything) 7/16" thick to 50 psf, and simply support it by the long edges, without any intermediate support, I calculate the maximum stress to be 3128 PSI which is unacceptably high for wood.
At 125 psf, the stress is 7819 PSI.

If the cover were steel plate, that would work.


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## BillConnerFASTC (May 14, 2014)

Well with two expect a change in the building code.


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## BillConnerFASTC (May 14, 2014)

A little more info. 2 students injured after stage collapse - CBS46 News

Does call it "temporary" and "student built". Could be OSB with a hardboard overlay.


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## JD (May 14, 2014)

Wow. I couldn't even fathom using "beaver board" for any type of decking, even on a 16" joist platform. You come down hard enough on it and even at close spacing it will break through. From the look of the picture, 16" spacing wasn't even in the same universe.


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## gafftaper (May 15, 2014)

Yeah those pictures look more like they were using 96" spacing.


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## rsmentele (May 15, 2014)

Definitely not constructed well... If it's student built, who was supervising?! I never use OSB, its just too spongie for me, even at 24" centers.


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## BillConnerFASTC (May 15, 2014)

I share your visceral reaction but, quoting the publication Builder:

To be sure, there is no difference between OSB and plywood as a structural panel, says APA - The Engineered Wood Association. The Tacoma, Wash.-based group is a nonprofit trade association that represents U.S. and Canadian manufacturers of plywood and OSB as well as other structural engineered wood products.

“Both products meet the local and national building codes,” says APA market research director Craig Adair. They are equally interchangeable for walls and roof sheathing, and for flooring underlayment, he adds. Moreover, both panels install fast and easily. Specified correctly, they perform as intended. Manufacturers from both sides claim their products offer better nail holding ability, but Adair says both meet the same requirements.

You can find less complimentary clips but at the end of the day, it's a material with known physical properties and can be used for structural floors.


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## TheaterEd (May 15, 2014)

gafftaper said:


> Yeah those pictures look more like they were using 96" spacing.


That was my first reaction as well, but if you look at the news story that Bill linked. The picture that is in the first ten seconds of the video is a shot of the hole from the other side. It looks to me like they framed it out with 2x6's but that they only used screws or nails to attach them to the vertical supports. It is pretty clear from what I can see that they didn't bolt them together.


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## gafftapegreenia (May 15, 2014)

TheaterEd said:


> That was my first reaction as well, but if you look at the news story that Bill linked. The picture that is in the first ten seconds of the video is a shot of the hole from the other side. It looks to me like they framed it out with 2x6's but that they only used screws or nails to attach them to the vertical supports. It is pretty clear from what I can see that they didn't bolt them together.View attachment 10785



In that shot, do you notice the ply attached to the bottom of the OSB? Odd construction, to be sure. 


Sent from my iPhone using Tapatalk - now Free


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## DuckJordan (May 15, 2014)

More over with the ply vs. OSB thing, most floors in your home the use OSB the cost if it where Ply on your floors would introduce on a 1500 sqft house would probably double the building cost without any real benefit. Thanks to working as a building carpenter for a year taught me some very valuable information for building decking.


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## BillConnerFASTC (May 15, 2014)

DuckJordan said:


> More over with the ply vs. OSB thing, most floors in your home the use OSB the cost if it where Ply on your floors would introduce on a 1500 sqft house would probably double the building cost without any real benefit. Thanks to working as a building carpenter for a year taught me some very valuable information for building decking.


I thought I read like $700 for a typical house. We all have our own priorities, and I choose plywood, but know that I'll be safe if its OSB.


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## gafftapegreenia (May 15, 2014)

From my experience in outdoor theatre, plywood holds up much better through a wet and humid Michigan summer.


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## josh88 (May 15, 2014)

My class is fixing up our paint ball course at the moment and there is both ply and OSB out there that's the same age. The ply is delaminating a little but the OSB is as flexible and floppy as wet cardboard. I'm surprised it hasn't just crumbled. Not the same situation as this, but yeah exposed ply holds up a bit better.

It's tough to see but that edge that's hanging over the black hole portion in the top right looks like it's super thin, like quarter inch OSB laid over the ply, strange indeed.


Via tapatalk


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## BillConnerFASTC (May 15, 2014)

I didn't see enough detail in the photos to reach a conclusion but there did appear to be a sub floor and a top layer and I wondered if the top layer was maybe mdf or or something other than hardboard.


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## derekleffew (May 16, 2014)

/off-topic Warning. DANGER. Link NSFW.
Obviously, suburban Atlanta government officials have more intrusive matters with which to be concerned:
Woman files suit over sex toy law | www.daytondailynews.com


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## LavaASU (May 16, 2014)

derekleffew said:


> /off-topic Warning. DANGER. Link NSFW.
> Obviously, suburban Atlanta government officials have more intrusive matters with which to be concerned:
> Woman files suit over sex toy law | www.daytondailynews.com


Well, yeah, tax dollars at work... clearly how two consenting adults choose to play in the privacy of their home is a massive crisis.


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## RickR (May 21, 2014)

My reaction is not about the surface. If I were investigating I would look first at the "legs" failing.

There is a high probibility of multiple problems.


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## TheTheaterGeek (May 22, 2014)

headcrab said:


> The broken edge does look like OSB.
> 
> If I load a 4x8 sheet (of anything) 7/16" thick to 50 psf, and simply support it by the long edges, without any intermediate support, I calculate the maximum stress to be 3128 PSI which is unacceptably high for wood.
> At 125 psf, the stress is 7819 PSI.
> ...



I wouldn't even do this with a steel plate.....

Yikes. 

I'm not super familiar on OSHA inspections. Isn't this something they should catch?


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## BillConnerFASTC (May 22, 2014)

TheTheaterGeek said:


> I'm not super familiar on OSHA inspections. Isn't this something they should catch?



When would you expect them to catch it? In my experience and observations, they don't "inspect" until after an incident and injuries - and unpaid people - like usually students - aren't covered.


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## BrianWolfe (Jun 10, 2014)

OSHA does not inspect like that. They come in after a complaint most times. The true failure is at the level of who gave permission to the students and the oversight of their work or lack there of.


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## venuetech (Jun 10, 2014)

It's something the local building inspector should catch. However it is very likely that a building permit was never applied for, so the inspector had no way of knowing that a modification had been made and needed inspection.
As Brian says

> The true failure is at the level of who gave permission to the students and the oversight of their work or lack there of.


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## robartsd (Jun 26, 2014)

BillConnerASTC said:


> I didn't see enough detail in the photos to reach a conclusion but there did appear to be a sub floor and a top layer and I wondered if the top layer was maybe mdf or or something other than hardboard.


 
It _shouldn't_ matter what the top layer was as the sub floor is supposed to be designed to provide all the structural support needed.


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## Les (Jun 26, 2014)

People just don't seem to realize how much liability you assume by building an extension like this -- and they think it can be built like a set or other temporary scenic element. 

Just be glad no one tried to roll that B-sized grand piano over it.


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## BillConnerFASTC (Jun 26, 2014)

robartsd said:


> It _shouldn't_ matter what the top layer was as the sub floor is supposed to be designed to provide all the structural support needed.


I didn't intend otherwise - it was in response to posts that suggested the structural layer was mdf or other, and I only commented I could not tell what was sub floor and what was surface or sacrificial flooring.


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## StradivariusBone (Jun 26, 2014)

Les said:


> People just don't seem to realize how much liability you assume by building an extension like this -- and they think it can be built like a set or other temporary scenic element.



The sad/crazy/unfortunate part is that you really don't know what you don't know. I see it happen frequently in the church atmosphere where you acquire really good-natured volunteers with their heart in the right place who have a knack for some aspect of building or wiring or whatever. They have tinkered enough in their garage to do some aspect of a project to give themselves enough courage to attempt something more, but you gotta always watch that line between residential and commercial (including schools and houses of worship). I really doubt anyone goes into this thinking, "Yeah, it'll last for a while and then 15 kids will fall through."

Just because you know how to do something, doesn't always mean you're the right person at a particular time and place.


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## Les (Jun 26, 2014)

StradivariusBone said:


> The sad/crazy/unfortunate part is that you really don't know what you don't know. I see it happen frequently in the church atmosphere where you acquire really good-natured volunteers with their heart in the right place who have a knack for some aspect of building or wiring or whatever. They have tinkered enough in their garage to do some aspect of a project to give themselves enough courage to attempt something more, but you gotta always watch that line between residential and commercial (including schools and houses of worship). I really doubt anyone goes into this thinking, "Yeah, it'll last for a while and then 15 kids will fall through."
> 
> Just because you know how to do something, doesn't always mean you're the right person at a particular time and place.




Ah yes. The art of knowing "just enough to be dangerous". The same reason why any rigging/pyro discussion was banned on CB for several years. It's a little more lax now, but still heavily moderated (justifiably).


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## StradivariusBone (Jun 26, 2014)

I hear ya. I feel like I've graduated to the level of "knows enough to be dangerous and is now self-aware of a personal capacity to be dangerous to self and others with the use of aforementioned knowledge".

Bertrand Russel said it well- "The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts."


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