Perma-Columns

[JCook5003]

Hey Guys-

I was wondering those of you who have had pole barns built with or have used Perma-Columns or sonotubes with brackets in D.I.Y. pole barn build could share how you added shear bracing for the Perma-Column or sonotube to post connection point.

From my light engineering (no degree) background, obviously a pole barn gets most of it's shear strength from the poles being buried 4' in the ground. When using a Perma-Column you've effectively moved the "moment loading" (I think that's the right term) point to ground level. The pole now acts more like a stud wall where it needs some kind of shear bracing. On a stud wall this is accomplished through the sheathing. Since it is common to add purlins with metal siding with a couple nails between the posts with metal siding screwed to the purlin, you don't get the same shear that you would with common stud framing. As a side note, the wind loading is 90MPH in my building department code book, pole barns dont get inspections though, but I do want to do it right.

My question is, how do you add enough bracing to make the structure sound again? Obviously not looking for an engineering report but some actual builds of things that work. I had though about using "commercial" or "ladder" style purlins in between my posts with the metal screwed through the flats into them. Then the metal acts much more like typical sheathing. Added side benefit of easy insulation and interior wall finishing.

Thoughts? Opinions?

 

[rieferman]

I used to be in sales for a pole barn company and we solely used Perma-Columns (never wood in directly in the ground).

It's been a long time, so I no longer have my support materials, but at the time, we had a series of points we'd take people through that basically showed:

- For Perma-Columns, the connection point between concrete and post is engineered to be stronger than the post itself (so you ARE getting the benefit of being 4 feet underground).

- Steel siding is comparable to plywood in terms of shear benefits.


As a side note, that company that I worked for face nailed girts to the posts (not book shelved). This is a speedy method with potential HVAC benefits should you choose to finish the interior later (a dead air space is created). Their buildings met the 90 MPH wind load requirements on their stamped engineering drawings.

Wish I could remember more, but hopefully this is somewhat helpful and others that are more currently in the trades can supplement this info.

 

[JCook5003]

I used to be in sales for a pole barn company and we solely used Perma-Columns (never wood in directly in the ground).

It's been a long time, so I no longer have my support materials, but at the time, we had a series of points we'd take people through that basically showed:

- For Perma-Columns, the connection point between concrete and post is engineered to be stronger than the post itself (so you ARE getting the benefit of being 4 feet underground).

- Steel siding is comparable to plywood in terms of shear benefits.


As a side note, that company that I worked for face nailed girts to the posts (not book shelved). This is a speedy method with potential HVAC benefits should you choose to finish the interior later (a dead air space is created). Their buildings met the 90 MPH wind load requirements on their stamped engineering drawings.

Wish I could remember more, but hopefully this is somewhat helpful and others that are more currently in the trades can supplement this info.

Thanks, i've seen the info on the Perma Column site, they claim the connection becomes stronger than a wood post also. I even think I saw a test run with breaking forces of a post, laminated post, perma column post connection point. They bent each to the breaking point and recorded the data. I've lost that bookmark though.

Maybe it's true, the 1/4 inch thick plate and big bolts are as strong as a continuous wood pole.

I've always just thought of it a hinge point, maybe that's wrong all together.

 

[DougWil]

If you have the tools and ability,,,,,
As expensive as perma columns are with shipping, I would consider a drilled hole, cast in place reinforced concrete pier, 4 anchor bolts, steel baseplate and tube steel column.

Any wood can be bolted via angle clips to the steel pole.

Perma columns have the right idea, but it is involved making that wood/steel moment resistant connection at the base.

Or even a spread footing and eliminate the drilling, like this drawing shows.

Nice to see you thinking that putting wood posts in the ground isn't the best long term plan.