embeded "pole" 1

[COEngineeer]

I'm going to embed a tube steel to act like a flag pole for house basement remediation. I already sized the member and I assume the bottom is fixed and top is free. Can someone help where to start so that my assumption of fixed bottom is met? How deep I need to embed it into concrete, reinforcement around the tube steel, etc. I will have about 15 kips-ft at the base and about 9 kips of shear. Thanks!

 

[twinnell]

Look in the wood chapter of IBC, there is a embeded pole equation that you can use. Also, if you download the Enercalc demo,there is an embeded pole foundation module you can use to check your work.

 

[twinnell]

Sorry, its not in wood. It is in chapter 18 - soils and foundations.

 

[miecz]

The PCI Design Handbook has a solution for a steel haunch embedded in concrete. It's in Section 6.9 of the 5th Edition. If you take the compressive force from the couple of that solution, you get the tension your ties need to provide.

 

[BigH]

Might want to check out:
Halder, et al "Full Scale Field Tests on Directly Embedded Steel Poles," Canadian Geotechnical Journal: 37 (414-437) 2000.

 

[swivel63]

the AITC (american institute of timber construction) has a method of determining pole embedment. it's an interative process, but relatively easy.

 

[csd72]

swivel63,
its an interactive process - you mean you actually have to get involved!?

Sorry but I couldnt resist this one, I assume you mean iterative.

csd

 

[LGARG]

HI Guys, i think that first you have to calc the depth of a pad footing to resit the overturning moment with the active/passive soil pressure.Then you have to calculate the embedment of the steel column in the pad. You could use the enercalc for that.

LG

 

[swivel63]

LOL, yea that's what i meant. for tubes imbedded into concrete for railings, i had to derive the real equation when i started working.

but i found that P/A +/- Mc/I came pretty close to the real answer. but this might be a lot different because we're probably talking about several feet of embedment.

 

[UcfSE]

What kind of base are you using? A pole embedded in the soil or embedded in a spread footing?

 

[COEngineeer]

into spread footing. Just design the concrete for the moment and look at the edge distance for break out failure i guess?

 

[UcfSE]

I would consider designing the base plate for the moment, not embedding the tube into the concrete. Your loads are not out of the reasonable range for this.

You can design the thickness of the plate with the AISC design guide, per Blodgett, Salmon and Johnson, or another if you have the reference and it is backed up with sound engineering. The bolts would be designed for tension. They may also be designed for shear unless you use a shear lug. If the bolts are taking the shear you should provide healthy plate washers with std holes to cover the oversize base plate holes and weld the plate washers to the base.

In your deflection calculations you should account for the additional deflection in the tube due to the footing rotation, anchor rod stretch and base plate deformation, depending on how sensitive your structure is to deformations.

 

[Lion06]

UcfSE-
That is a good point about the initial deflection due to footing rotation, anchor bolt stretch, etc. Do you have any references to point to on this?

 

[csd72]

If it is a big tube with a thin wall, watch the buckling of the tube when it is bearing against the concrete.

 

[Lion06]

csd72-
I have given some thought to this recently. If you have a compression member with a very large radius of gyration so that the entire member won't buckle globally, but the wall is very thin, how do you check local buckling of the wall. Where do you look this up?

 

[miecz]

StructuralEIT-

In regard to the footing rotation, anchor bolt stretch, and base plate flexure, I have a handwritten solution. However, I don't have a reference for the solution, and, it is too long to post here. If you post a fax number or email address, I'll send it along to you.

Table 35 of Roarkes formulas for Stress and Strain has a solution for a thin walled circular tube under uniform compression and under compression due to bending.

 

[Lion06]

jmiec-
Do you know if there is anyway to post something privately without displaying my email address to everyone?

 

[civilperson]

Not suppose to do that. We will spam you with out mercy!

 

[Lion06]

That is why I asked if there is a way to post it privately.

 

[UcfSE]

Click on "My Info" under the Eng-Tips logo in the upper left. At the bottom under your participation record,

"This site gives no personal information to anyone for any reason. Please don't post your e-mail address or phone numbers because it attracts salespeople, spammers, and stupid recruiters to the forums and we do NOT want them around. This site works the best when conversations are kept on a technical level. Thank you."