Post embedment for pole barn 1

[AsianEngineer]

We don't usually do pole barns in our office so I'm not quite sure if the embedment I got is typical or not. So, I wanted to ask if a 8ft embedment for a 20 foot post sounds about right. I know their are other factors that you will need to know for the design, but I was just curious if this sounds about right to you.

 

[oldrunner]

How can you ask if the embedment is correct if you don't mention what the loads are? Do we have 80 mph winds or 130 mph wind? You know there are others factors but we don't know what they are. Is you building enclosed or open?

The American Wood Preservers Insitute published "Pole Building Design"; my edition is 1970. There is "Design Notes and Criteria - Pole Type Buildings" by Degenkolb and Associates (San Francisco) that was published for JH Baxter.

Google to see if some of these publications are available.

 

[yywcn]

Soil type, esentailly k value, pole diameter are key parameters to determine the embedment depth, as well.

Brom's method gives your some idea. good luck

 

[BarryEng]

http://www.eng-tips.com/userinfo.cfm?member=SlideRuleEra

Check with SlideRuleEra - he has a web site with info on pole structures.

 

[BarryEng]

I thought I'd lost his contact, but I just found it.
Try

http://www.slideruleera.net/

for info on wind loads on barns & pole embedment depths.

 

[GOODER30]

Does anyone have a "Pole Barn desin example". Things have changed since the publications on

http://www.sliderulee

ra.net/ website. (I think they have changed) I
heard that Diaphram action is considered more in design these days. I am just looking for how to design a pole barn the right way using the right calculations. If anyone can point me in the right direction that would be great.

 

[WBUW]

Well I can give you a basic run down of how I used to do them.

Calc your lateral loads, seismic and wind. Remember that each pole is a cantilevered column, you will have to alter your R value to accommodate that.

Calc your gravity loads.

Size the pole using combined action, flexural and axial. Be sure to consider the critical direction. The higher the post the larger the size required, it will get nasty pretty fast. Contractors seem to think a 6x6 with a 4' deep 24" diameter is all they ever need to do, but when you start increasing the height or the spacing of those posts...

Depending on design method used you can increase the strength of the pole a certain percentage, eg ASD you can use 1.6 for wood.

Depending on which theory you subscribe to you may consider the girts to brace the system, or you may not. *shrug* This will only help in one direction anyway.

The embedment depth can be determined using IBC 1805.7.2 in conjunction with table 1804.2 They were probably cheap and didn't get a geotech report (thats why they are building a pole building) so you will be SOL on the values, the code requires you to assume pretty darn poor unless you are willing to assume / prove some better soils are out there.

The diaphram calcs are a bit more difficult. Values for the corrugated metal roof exist, but you will have to find them on your own. I did this a while ago and it was a pain.

If you resort to making them use OSB or CDX, expect alot of complaining. You can buy 'A Primer on Diaphragm Design' from the MCA, but it'll cost you and its not the easiest read. Testing values from McElroy or another major manufactuer are probably easier to obtain.

You should already be familiar with how to calc diaphragm demands or you really shouldn't be doing this.

Thats a basic rundown. Connections are pretty staightforward, other than the diaphragm calcs.

My advice to you is run a few calcs ahead of time, see how things turn out and let them (meaning the contractor / builder, the owner will just go 'okay' then come back screaming about the price later) know so they can't come back later on and complain.

All in all if the moaning and whining gets to be too much tell them to go perscriptive and wash your hands of it. Make sure you get the money up front.

Sorry, not a real positive review, but thats been my experience with these buildings. Cheap, cheap, cheap and more cheap.

Good luck!

 

[msquared48]

Typically with no knee braces to the columns, I have been able to use for 85 mph winds, 12' eaves, 12' bays, 6X6 RC PT HF#1 columns, with double premanuf. trusses at each colimn, and 4 to 6' burial on a 18 to 24" diameter augered hold filled with lean concrete. Lots of variations from that though. Column sizes go up as wind and eave increase.

Mike McCann
McCann Engineering

 

[RHB51]

AITC manual(American Institute of Timber Construction) has a large section on pole barns with example problems.
If you cannot obtain a copy I would be able to fax some of it to you.
Randy