And another high school pit cover failure

[gafftapegreenia]

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

 

[headcrab]

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.

 

[BillConnerFASTC]

Well with two expect a change in the building code.

 

[BillConnerFASTC]

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.

 

[JD]

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.

 

[gafftaper]

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

 

[rsmentele]

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.

 

[BillConnerFASTC]

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.

 

[TheaterEd]

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.

 

[gafftapegreenia]

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.


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[DuckJordan]

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.

 

[BillConnerFASTC]

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.

 

[gafftapegreenia]

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

 

[josh88]

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.


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[BillConnerFASTC]

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.

 

[derekleffew]

/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

 

[LavaASU]

/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.

 

[RickR]

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.

 

[TheTheaterGeek]

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.

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?

 

[BillConnerFASTC]

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.