Large Sign Pole Design
Large Sign Pole Design
(OP)
I have been asked to design a 65ft tall pole for a sign. See attached dimensions. They want a break at 25ft, and then another pole break at the sign which is supposed to have a HSS Tube behind the sign for attachment. Does anyone have any ideas on how to attach these together besides a plate splice with bolts? Is there a way to do some sort of sleeve at the first break from the ground so it looks a little bit cleaner?
I imagine there will be some sort of frequencies that need to be considered with this as well.
Thanks
I imagine there will be some sort of frequencies that need to be considered with this as well.
Thanks






RE: Large Sign Pole Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
RE: Large Sign Pole Design
I bought it a decade ago after my first sign and it's been shelfware ever since. Six homes and two countries later, somebody finally asked the right question. I pretty much trampled my wife on the way to the basement to fetch the detail.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
RE: Large Sign Pole Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
RE: Large Sign Pole Design
RE: Large Sign Pole Design
Nope.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
RE: Large Sign Pole Design
RE: Large Sign Pole Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
RE: Large Sign Pole Design
RE: Large Sign Pole Design
Sail3: my first inclination before KootK sent the detail was to let the pipe slide down into the larger pipe 3-4ft, but then realized it probably would be unstable. The welds certainly will be expensive, but so far, I haven't seen anything different or another method. The forces are to great to do a standard plate splice with gussets, so the sleeev solution seems to be it.
RE: Large Sign Pole Design
How many separate pieces do you expect this thing will be in when it ships?
Also, do you know the minimum access hole size that will be required for wiring etc?
When they step ski lift and utility poles, there's sometimes a truly tapered bit at the transition. I could see that being expensive for a shop not set up for that though.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
BA
RE: Large Sign Pole Design
(1) Large pole for the base...probably a 32 Std pipe
(1) Smaller pipe for the piece between bottom pole and bottom of sign
(1) HSS from the mid pipe for sign attachment that I will do a typical plate splice with on top of the pipe. I think the HSS will provide for more reliable connection of the sign.
Not sure on access hole sizes.
RE: Large Sign Pole Design
RE: Large Sign Pole Design
RE: Large Sign Pole Design
RE: Large Sign Pole Design
the lateral loads coming into the lower tube at a line of welds ... do you like that ? I understand it is a difficult design to link the two tubes. You could use a bolt on sleeve ... fits inside the lower tube, outside the upper, several cross bolts into each tube ...
another day in paradise, or is paradise one day closer ?
RE: Large Sign Pole Design
Care to explain this comment Koot? I only see the fillet welds resisting shear, but I am sure there is something I am missing.
Thanks!
RE: Large Sign Pole Design
Actually, if I’m reading you comment about the pairs of fillet welds taking the bending action correctly (as you intended it), those welds really aren’t that unusual. Take a unit width (unit circumferential length) of the ring pl. at those welds; with a canti. length of [(D1 - D2)/2, +/-], the radial space btwn. the pipes, +/-; the gravity and lateral loads cause bending on the double fillets, plus shear perpendicular to and in the plane of the ring pl. This doesn’t really load or stress the welds appreciably differently than on a “T” joint with a tension/compression load on the “T” web, plus a bending force on the web. And, we see this detail quite often in everyday service. The important thing about the double fillets, and bending, is that they tend to protect the fillet roots, they prevent prying tension across the roots. Then, the resisting moment is the ring pl. thickness, plus, times the fillet weld cap’y. per inch of circumferential length.
RE: Large Sign Pole Design
RE: Large Sign Pole Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
I'd also recommend against 32" pipe and use either 30" or 36". Much more common and you can get them in almost any thickness from .312" and above(.375/438/500 etc.) 20" and 24" are also very available for the second stage. Most people in this business will have these pipes in stock.
Personally, I like the 'optional' guide ring shown in that detail and usually use something thicker. I have seen an instance where the field welds were done improperly (horribly) and that guide ring would have saved a failure that couldn't be repaired.
RE: Large Sign Pole Design
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Large Sign Pole Design
Looking at this one, I'd expect it to be shipped with the top two stages shop welded together. They'll plant the lower column in the ground then drop in the top piece and field weld it at the 25' level. So field welded in the air. It's difficult to manage pipes like this horizontally. We have rollers in the shop to help...but even then it can be a pain. Gravity is a big assistant. That being said, that one field fillet will be an overhead weld so the welders need to be qualified. That's much easier in the shop with the powered rollers in a horizontal position.
Biggest problem we see (fabricators perspective) is when a pipe is assumed to be perfectly round and it's not, the nice circular rings won't fit. And you can't assume a factory end on pipe is always square. We test fit connections to be field welded.
RE: Large Sign Pole Design
1: is it common to use a HSS at the top for the sign to hook to, or do another pipe and sleeve?
2: for foundations, it's pretty big. Like 5' diameter X 16' deep. Is it more common to go shallower or a balance?
RE: Large Sign Pole Design
2. That's not terribly deep from my perspective. Obviously, I don't know your site conditions. Personally, when possible I usually opt for smaller diameter and a bit more depth. For a 30" pipe I like a 4' diameter pier which would add a couple feet to your depth. Water table or other considerations also come into play there. I also try to avoid reinforcing the annular space and consider the concrete 'soil improvement.'
RE: Large Sign Pole Design