30' vertical pipe stiffness

[TeejT]

I need to figure out what the minimum size of 30' long pipe is that would not significantly wobble (a few inches at most) in "average" wind conditions when C-clamped to a ~ 1000+ lb anchor bolted to concrete with concrete bolts. C-clamps would be used at ground level and ~ 5' above ground level. Any clues how to approach this or personal experience to give me a ballpark size?
Thank you!

 

[kacarrol]

I would think you could use basic Mechanics of Deformable Solids calculations. This sounds like a cantilever beam with a distributed (wind) load.

http://www.advancepipeliner.com/Resources/Others/Beams/Beam_Deflection_Formulae.pdf

You may want to look into harmonics also, to be sure you don't hit a natural frequency.

 

[TeejT]

I did think of that, but where can I get wind loading data for different wind speeds and different diameters to actually apply this?

 

[Cockroach]

30 ft length of pipe, methodology for support at the base, okay. What is the OD and wall thickness? What is it made from?

I can't see you just Hilti it to the concrete and calling it good. That is going to be a huge turning moment at the base given a few inch deflection at the top of a 30 ft pipe! You may need to pour a concrete support.

Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada

 

[TeejT]

Cockroach,
The OD and SCH wall thickness is what I'm trying to determine! It would be a continuous length of galvanized steel pipe. There is no option to pour more concrete but I am anchoring it with U-bolts to a 5' vertical metal beam on machine that weighs 1000+ lbs and is bolted down into concrete (so it's probably immovable).

 

[ivymike]

drag equation:

http://en.wikipedia.org/wiki/Drag_equation

drag coefficient vs reynolds number:

http://scienceworld.wolfram.com/physics/CylinderDrag.html

wind gradient info:

http://en.wikipedia.org/wiki/Wind_gradient

 

[TeejT]

Alright, I think I know what I'm doing now:

1. Calculate wind loading on PIPE MAST (Cd = 1.2 for cylinder)
2. Calculate wind loading on square antenna (Cd = 2.0 for flat plate)
3. Represent wind loading on PIPE MAST as uniformly distributed load and calculate max. displacement at tip due to uniformly distributed load.
2. Represent wind loading on SQUARE ANTENNA at the top as point load and calculate max. displacement at the tip due to that point load at tip.
3. Sum the two max. displacements to obtain total displacement at tip.

Does this sound reasonable? Thanks again!

 

[desertfox]

Hi TeejT

This might help:-

http://www.acmelingo.com/flagpoles/FP1001-07.pdf

and this

http://www.risatech.com/downloads/risatower/Technical_Manual_1.pdf

desertfox

 

[TeejT]

Hi desertfox, those are overkill for this quick & dirty (& cheaper) solution but but I've added them to my technical manuals library. Thanks!

 

[MikeHalloran]

Are you sure you can get a 30 foot length of pipe in one piece?

Maybe you don't want to, anyway. Look at, e.g., the poles used to support billboards high above expressways. They're stepped, made from several diameters of pipe. Larger pipe toward the base makes it a little easier to deal with the moment.





Mike Halloran
Pembroke Pines, FL, USA