Pole Barn Question

[SteveBenson]

I think what 5string is saying (and maybe you're are planning on doing it already) is to make sure that you still add some diagonal bracing even though your building doesn't have sides. Your building will still be subject to significant shear loading due to wind load on the roof. Also, sufficient bracing is especially needed if you are building on piers as you get no shear support from the embedded poles. Diagonal bracing is hugely important in metal sided pole buildings. Unlike plywood, metal siding adds no shear strength (to thin and prone to buckling). Metal strap bracing is an ideal solution in combination with metal siding.

You can design a building that can take all the up and down loading you can imagine, but it's usually that side load that will come along an topple it over.

 

[Junkman]

My posts moved in all directions.... front to back, side to side. Around here, the frost gets deep into the ground and it is not rare to see -20 degree weather for a week... as for wind, yesterday, my wind meter topped out at 75 MPH. I don't know exactly how hard the winds were blowing, but 2 pine trees blew down from the wind and the heavy soaking rain. I am posting a picture of the foot that I used. You cut the slits out for the size of tube that you are going to use and slip it into the center and lower into the hole. They foot is marked for each size tube so it is easy to do with a sheet rock knife. My mistake was not backfilling with sand. Had I done that, they might not have moved. I have since worked around the problem and it is resolved.
As for what some other people have mentioned, you will need cross bracing. I suggest that you use 2 x 6 PT and "let" them in. That means that you hold the board against the uprights at an angle and then mark where they board will meet the uprights. Then using a circular saw, make two cuts on the lines that are the depth of the 2 x 6... (1 1/2"). Then you chisel out the area between the two cuts and put the board into the cut out area. This will give you the most strength for diagonal bracing.

 

[dmccarty]

Cowboydoc,

That is good to know about your barns.

I'm not that worried about the high winds. This barn, as well as
our house and garage to be, will be buried in the woods. If we
have high winds I'm not really worried about the barn falling
down as much as I am about the trees falling down on the barn.

My father in law still has a mess of trees on his house from our
last hurrican.... 8-(

We are removing the trees from the house site but back by the
barn they are staying.

Having said that, I am doing the structural design to get it right
so I do appreciate all of the comments that are showing up in
the thread. Its cheap to make a change right now since its all
in my hand and in the CAD software!

Later,
Dan

 

[dmccarty]

Junkman,

Now that is an interesting footer/form. The ones I have seen
are only tubes which still require a footer or they have an
Elephant foot which just does not appear large enough for what
I want todo. I figure I'll have to get what you used or build my
own footers. The "book" sais the footer should be a minimum of
8" thick and I think 7" from the edge to the pier/foundation wall.
Soooo, I thinking of building a 24" square by 12" deep footer
under each pier. But your footer form looks interesting. Much
faster to do your way......

How did you fix your pole movement? Sounds like using ABC
will firm things up around the pole. That stuff is almost like
concrete once it settles...

Thanks for the ideas!

Later,
Dan

 

[cowboydoc]

I'm not really worried about the barn falling
down as much as I am about the trees falling down on the barn

Yes I agree with you there. Those dang trees can do alot of damage in a hurry.

 

[5string]

Yes, that is basically what I was saying. Thanks for clarifying my post. I just wanted to be sure that Dan did not discount the potential shear simply because his structure will not have sides (or will it); it sounds like he is doing his homework.

A previous post indicates that the airfoil theory only comes into play when one side is closed-in and the air is not allowed to pass through the building; this is not the case. Actually, the addition of a wall at one end which impedes air flow will lesson the lifting loads. Air on the bottom and top try to meet at the same time at the opposite end (same volume). Since the air on the top has a greater distance to travel (roof pitch) it must move faster. It is this relative increase in velocity and proportionate decrease in pressure on the top surface which generates lift. In my area we also have many open pole structures . The majority ( the one's that were a kit or engineered) have a one or two ft. skirt that extends down from the bottom edge. Although it provides a nice finished look, it's real purpose is to break-up the airflow along the bottom surface so the air rushing over the top is not accelerated (venturi effect).

The one sided structure scenario raises other concerns - primarily torsion (large twisting moments from swirling gusts).

 

[Junkman]

</font><font color="blue" class="small">(
How did you fix your pole movement? Sounds like using ABC
will firm things up around the pole. That stuff is almost like
concrete once it settles...

Thanks for the ideas!

Later,
Dan

)</font>

I did it the old fashioned way...... just waited a year for it to settle to where it wanted to be and then built on top of it. It being a deck that is attached to the house, I don't have any more problems because there is no wind or sheer factor that I know of....

 

[dmccarty]

mytoys,

Now that I have somehow all but highjacked your thread, did
you get the answer you needed?

Later,
Dan

 

[mytoys]

Dan,

No highjacking at all. The beauty of this forum is that the threads are very informative and they can go in any direction depending on who contributes. I have definitely gotten loads of information to think about. Thanks to all!