diameter of pole strength?

[adelaide]

any 1 got a table or know a easy way of explaining the diff load / thrust back a pole can take if the poles are say same thickness how many times stronger is a 4 inch (diameter) pole than a 3 inch in push back force say 2 meters down to its gye wires / wall , ty

[dudevato]

if no one answers here - here is a link to a welding site I'm on - guys there build bridges and know a lot about metal.  http://www.hobartwelders.com/mboard/forumdisplay.php?f=4

[whatsnext]

Try the ASME's website or whatever website the civil engineer guys have. Your question of "what will it take?" is going to be a tough one to answer because only you know what level of safety you will accept and exactly how the loads will be applied to your tower.

[SmoggyTurnip]

The deflection of a steel pipe with a force at one end is given by:

Deflection = (F * h^3)/(3*E*I)

Where

F = Force

h = Height

E = Young's modulus for steel (30*10^6 psi)

I = (PI/64)*(OD^4-ID^4)

PI = 3.14

OD = Outside diameter

ID = Inside diameter

.

[kitno455]

i dont know an 'easy' way, but i can give you some pointers to some math to google. fortunately your choice of round hollow section is the easiest to figure.

'radius of gyration' is what you are varying with larger pipe:

http://darkwing.uoregon.edu/~struct/courseware/461/461_lectures/461_lecture30/461_lecture30.html

'effective length' is modified by how the ends of the section are held, rigid fixures decrease effective length, free ends increase it.

'slenderness ratio' is based on the above, and helps you figure out most likely form of failure.

you will also need some data on material properties, but they are pretty generic for steels.

allan

[wdyasq]

So, the rigidity is a 4th order property and the strength is the 3rd order...

Ron

[wpowokal]

I personaly use the cross section area ratio, I can't technically prove it because I'm too lazy to find the text books.

Others have given you the apropriate formular and site pointers anyway.

So by my rule of thumb 25% stronger.

I personaly subscribe to larger diamiter thiner wall, unfortunatly tower design is a complicated issue, I have had a couple of ups and downs myself.

allan down under

[windstuffnow]

Smoggy, so what is the deflection units... if force in lbs and height in feet.   Deflection in Feet?

[SmoggyTurnip]

Force is in pounds force.

ID is in inches.

OD is inches.

h is inches.

Deflection is in inches.

.