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[Ashley Boudreaux]

As noted - the ernie mills hi-rez photo sequence shows the towers were intact thru start of collapse - you can see if you look really close the guy at that SR front outrigger snaps - and that is when the legs shear ... seems pretty clear the guy snapping released a big shock load of energy which caused the shearing, or at least allowed enough movement toward SL that the lateral load snapped towers

Ok, I'll look again, and will also review my post to make sure we're talking about the same thing.
But back to the ballasts. Water tanks? concrete? Where is it? I'm used to seeing concrete or water tanks, and for the life of me, I can't find either in the photos or videos. And how can that be OK? I work on stages but I don't design them, so if there's something I'm not understanding here about what I've always perceived as the critical need for ballasts, then I humbly seek clarity from those more experienced.
Thanks y'all.

[ScottAllan]

 further insight into this tragedy:


Indiana State Fair incident was no Fluke!
http://wxbrad.com/?p=1450

Smarter phones smarter weather
http://digitalmeteorologist.wordpress.com/2011/08/16/smarter-phones-smarter-weather/

Indianapolis Tragedy Not a Fluke by Tim Ballisty, Editorial Meteorologist The Weather Channel
http://www.weather.com/outlook/weather-news/news/articles/indianapolis-tragedy-not-a-fluke_2011-08-15

Capital Weather Gang at the Washington Post
http://www.washingtonpost.com/blogs/capital-weather-gang/post/indiana-stage-collapse-was-it-preventable/2011/08/15/gIQAvXa9GJ_blog.html#pagebreak

The Fundamental Problem at the Indiana State Fair (Mike Smith)
http://meteorologicalmusings.blogspot.com/2011/08/fundamental-problem-at-indiana-state.html

Anything but a “fluke” (Brandon Redmond)
http://swatchasers.wordpress.com/2011/08/15/anything-but-a-fluke/

Indiana State Fair Stage Collapse JOHN HUNTINGTON
http://www.controlgeek.net/

 Chuck Doswell Magnifying a Tragedy (Very Good Read)
http://cadiiitalk.blogspot.com/2011/08/magnifying-tragedy.html

[ScottAllan]

Another comment from a blog:

The Indiana State Fair had a meteorologist on staff. According to Fox59 news this evening, he suggested an evacuation at 8:15pm.

Add's another whole layer of concern ... if true - why did they ignore their meteorologist?

[paul bell]

The picture below does NOT show cross bracing. It is HORIZONTAL BRACING which will not prevent the box section from moving. They offer zero strength in the diagonal.

"CROSS BRACING" is additional reinforcement beams or struts which are attached diagonally to the top left and bottom right corners and top right and bottom left corners of a box frame. This produces what looks like a X. This provides strength diagonally in tension and compression.

Adding horizontal bracing adds virtually no strength to the structure.

These large truss stage structures need cross bracing on the rear and side walls and across the roof.

Ballast, whether it's water tanks, concrete blocks, filled dump trucks etc. (weight is weight) needs to be added to these structures to help secure a solid ground base and add anchorage.

I'm posting this because the bracing in the photo has been incorrectly referred to as cross bracing, and there was discussion of the pros & cons of water ballast vs. concrete blocks.

[Brian Faulkner]

Indiana Fair Board has announced that they did not follow their own guidelines for warnings and evacuations. Wish TV ran the story. However they only admit fault in the wording used not in the timeline.

[ScottAllan]

Ok, I'll look again, and will also review my post to make sure we're talking about the same thing.
But back to the ballasts. Water tanks? concrete? Where is it? I'm used to seeing concrete or water tanks, and for the life of me, I can't find either in the photos or videos. And how can that be OK? I work on stages but I don't design them, so if there's something I'm not understanding here about what I've always perceived as the critical need for ballasts, then I humbly seek clarity from those more experienced.
Thanks y'all.

This prior post includes info and a great video from Chopper

http://forums.prosoundweb.com/index.php/topic,4255.msg23217.html#msg23217

It is pretty clear the back corners of stage were guyed to single concrete barrier sections - that were sitting on blacktop

[Dan Costello]

The picture below does NOT show cross bracing.

Yes, it does. It's hard to tell if there are any on the back wall, but there most definitely are diagonal cross-bracing cables on the side walls. You can see the spansets for these cables under tension at the joints between the horizontal braces and the vertical legs. IMO, they're easiest to see on the SL wall.

-Dan.

[paul bell]

Yes, it does. It's hard to tell if there are any on the back wall, but there most definitely are diagonal cross-bracing cables on the side walls. You can see the spansets for these cables under tension at the joints between the horizontal braces and the vertical legs. IMO, they're easiest to see on the SL wall.

-Dan.

Cabling is not cross bracing. It only provides tension. Compress it and it becomes slack offering zero rigidity. For this type of structure, ridged compression and tension bracing across diagonal points should be used.

[Dan Costello]

Yes, it does. It's hard to tell if there are any on the back wall, but there most definitely are diagonal cross-bracing cables on the side walls. You can see the spansets for these cables under tension at the joints between the horizontal braces and the vertical legs. IMO, they're easiest to see on the SL wall.

-Dan.

Cabling is not cross bracing. It only provides tension. Compress it and it becomes slack offering zero rigidity. For this type of structure, ridged compression and tension bracing across diagonal points should be used.

That's why you use two sets of cables connecting opposite corners of the rectangular area to be secured - the cables provide counter forces to each other. As the structure moves in one direction, certain cables will, as you point out, tend to go slack. But as this happens, the other set of cables will be under greater tension and provide a force to resist that motion.

Hopefully someone else with more of an engineering background can chime in on this, but I know that other structures use cable supports in this fashion. Airplane wings are one example, and I'm pretty sure I've seen them in glass & steel buildings where beams don't fit the visual aesthetic. Cables can provide a great deal of structural support while weighing far less than beams.

-Dan.

[Jeff Bankston]

Yes, it does. It's hard to tell if there are any on the back wall, but there most definitely are diagonal cross-bracing cables on the side walls. You can see the spansets for these cables under tension at the joints between the horizontal braces and the vertical legs. IMO, they're easiest to see on the SL wall.

-Dan.

Cabling is not cross bracing. It only provides tension. Compress it and it becomes slack offering zero rigidity. For this type of structure, ridged compression and tension bracing across diagonal points should be used.

+1. rigid X bracing(not cables) provides strength and rigidity in both compression and tension. cable X bracing will only provide rigidity and strength in tenson not compression but its better then nothing at all.

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