Tent anchorage.

[connect2]

Hi,
Taking a look at the anchorage for wind loads of a tent structure about 60' x 120'. Does anybody know where to find references to determine capacity of the anchorage rods driven into ground? In this case the rods are 1" dia x 18" long and subjected to both lateral and vertical uplift loads simaltaneously.
Thanks.

 

[CANPRO]

Obviously very dependant on the soil and if its only 18" into the ground I'd imagine the soil conditions vary quite a bit around the tent at that depth. Not sure about references, but with a rod that size I'd probably step outside the office drive it into the ground and get a feel for it myself.

 

[connect2]

Hi CANEIT
Yes we can test it, and yes the conditions of the soil will vary with the depth and somewhat with area.

 

[Gumpmaster]

I've, unfortunately, had to deal with the same situation.

I would never place my stamp on the tent peg into the ground concept. There's just too much variability and you never really know what the capacity is. The soil can change if it gets wet, dry, ....

When asked to do this I've said that if you want to use tent pegs, then that's on the tent manufacturer, I won't touch it. If you want to have something that's guaranteed to work, then here's a concrete block that you can anchor to.

Are you willing to stamp a tent peg?

 

[gwynn]

I agree with Gumpmaster. Unless the "tent pegs" are closer to being piles or pole foundations than tent pegs, I would look for different means of anchoring the tent structure.

I've looked at somewhat similar scenarios, where the peg was only subjected to horizontal loads, and even if you assume decent and consistent soil capacities the peg capacities are not near what I would expect are required.

 

[connect2]

Hi All,
Yes it's rather nebulous. Normally we haven't been involved much in this type of thing, re Temporary Tent Structures, Temporary Stage structures etc. However there have been several stage collapses in the last several years and local City Building Departments are now requiring an engineers involvement. As I've driven by, or attended some of these large events and the tents, stages, etc., I always wondered who sorted it out so to speak. Of course the 'tent' contractor is totally baffled by my question re peg capacity. The only thing I can think of is to drive some pegs, they are 1" dia x 24' long into some 'Saturated soil' on the site and test them. Compounding the unknown in my case are the pegs are in groups of 4, with each peg 8" apart. The engineer that sealed the tent requires each peg be able to develope '2400 lbs of capacity in pull-out'.

 

[JedClampett]

I'd make them change to an anchorage that you can document capacity for. When I did a search on soil anchors a lot of literature came up. This one seemed promising

http://www.americanea.com/

Also

http://www.nae.usace.army.mil/reg/nrrbs/technical-supplements/ts14e.pdf

The fact is that the reason you're involved is that the way they used to do thing is not working. We don't use leeches anymore to cure illnesses (well maybe some people do). They might need to get away from pegs to something a little more engineered.

 

[connect2]

Thanks JedClampett. Both sites are interesting!

 

[MikeHalloran]

<tangent>
A couple of years ago I was living in South Louisiana, and USACE came in to build a concrete floodwall, which was anchored by what amount to tent pegs; WF sections, maybe 18 inches deep, thick, and 133 feet long, too big to ship by truck, so they came by barge.

What I found fascinating was that as the pegs were maneuvered into a tilted frame in which the pile driver ran, as soon as they were released they would sort of ooze into the soil, driven only by their own weight, to a depth of as much as fifty feet, before the hammer was ever attached. ( Then they were driven flush to the bottom of a ten foot deep pit, and a rebar structure was welded to the top of an array of pegs, and the pit was filled with concrete, and became part of the base of a poured wall. )

One of the crane operators lived in the adjacent trailer. He said that when the hammer came down, he could watch waves rippling out from the point of impact. That's waves, like on water, but in what otherwise appeared to be solid ground.

Well, okay, solid ground is kind of an ethereal concept in that area; New Orleans stands on a thousand feet of somewhat compacted Mississippi mud deposited on the bedrock.

I have to admire the courage/hubris of USACE.

</tangent>

Mike Halloran
Pembroke Pines, FL, USA

 

[OldPaperMaker]

connect2,
If you go to

http://www.earthanchor.com

you can check out the capacity of their Mantaray or Duckbill anchors.

 

[JStephen]

Would it be possible to use some sort of waater-filled container as ballast? I'm envisioning something like large bladders filled on site.

 

[XR250]

You could use mobile home anchors. I imagine there is some capacity tables for them somewhere.

 

[PEinc]

I believe I read an article about helical anchors being installed permanently into accessible, covered boxes, in order to anchor large tents in Washington DC an the Mall lawn. When needed, the boxes are opened and the guys are attachedto the anchors. When not needed, the boxes are closed and are flush with the ground surface so the lawn can be mowed.

http://www.PeirceEngineering.com

 

[PEinc]

http://www.foundationrepairnorthflo...ee-fl-foundation-structure-stabilization.html

http://www.PeirceEngineering.com

 

[bigmig]

I realize this answer is a little late, but for whoever is reading, maybe it will apply. Why not do some field testing....drive some and pull them out. Apply a comfortable factor of safety to a comfortable group of tests. I believe the IBC covers the required parameters for doing in-situ testing. In addition check out ASCE7-10 section 1.3.1.3.

The idea that you can't use something that people have been doing since the dawn of time simply because it doesn't exist in a book is fantastic. It means you are pushing the envelope, which is what engineering is all about. After you test, help us all out by posting a quick blurb about your results, final decisions etc.