Removeable or replaceable verticle poles on pole building design

[fastline12]

http://eng-tips.com/viewthread.cfm?qid=350745

I created this thread in the ME section requesting ideas for replaceable poles in a pole building. We live in Tornado alley so designing for total failure has to be considered. Please feel free to post in this thread or the link above.


Thanks

 

[Jerehmy]

Why do you have to embed the poles? Use a wood to concrete connector at grade. Use the roof as a diaphragm and have shear walls. Treat the column as pinned instead of fixed.

The embedded pole has only partial fixity and if your using it as a laterally stable pile IBC requires a minimum of 5ft btw.

 

[msquared48]

Jerehmy:

Embedment of the poles is the name of the game for pole buildings.

Mike McCann
MMC Engineering

 

[msquared48]

It would be much easier to create a breakaway moment connection our of steel than wood.

Are the poles wood or steel?

Mike McCann
MMC Engineering

 

[fastline12]

Pole building design has been proven to be very sturdy in high wind vs concrete/base plate connection. They are cheaper, faster, and stronger in many cases. However, if that means a structure that will only hold up for 30 years, that is not acceptable. Our building codes have guidelines for embedment based on spacing and wall height. We may go more than 4ft but with shear locks, I don't think it will be needed. The failure at grade is the last straw.

 

[Jerehmy]

Msquared48 - I know. I have the NFBA Post-Frame Building Design Manual sitting in front of me, and I just finished designing a pole building. They embed the poles but most of the load is resisted by the diaphragm and shear walls. I couldn't imagine the size of your columns if they were the only member resisting wind.

So if the poles aren't contributing much in the first place, and they may need to be replaced in the future, why not just make it a pinned connection? Simpson has plenty of connections for this. The connection only cost a few dollars and doesn't add anything to labor fees. You made need a slightly strong diaphragm and shear wall, but that's inconsequential.

 

[msquared48]

I agree if the system employs shear walls, but then if is not a true "pole building" then.

Mike McCann
MMC Engineering

 

[Jerehmy]

In the reference thread it was stated that the building would be using wood columns, so i assumed it's just a simple wood building.

The NFBA has tables for shear capacity for 28-30 gauge sheathing so if they aren't using a diaphragm and shear wall for wind loads, maybe consider it?