Wood light pole base

[braves25]

Hello,

Has anyone designed a light pole base for a wood poll? I have a 14' wood post (8x8) with a single fixture a the top. The owner wants a concrete footing (drilled pier or square, I don't think that matters to them) and a fabricated steel base connection, that is connected to the wood post with bolts. Anyone had success with this type of connection. Critical areas to consider in the connection design? Thank you and have a great day.

 

[phamENG]

It probably would, but finding a hole saw that deep would be hard enough - making it go in straight would be even harder.

 

[r13]

Other than difficult to core, any shrinkage concern between the pipe and wood, and the base connection?

 

[JoelTXCive]

I have a blast from the past. JAE did some wood moment bases several years ago. I saved the picture he posted, but I do not remember the name of the thread.

He had multiple posts, so was able to create a system of moment resisting columns. Unfortunately, you just have 1 post.

There might be other good info in the thread though. Or JAE might see this post and remember.

 

[KootK]

It's too bad that one can't count on a slotted hole to not bind up. Otherwise, you might slot the anchor bolt holes and provide connection angles that move with the wood shrinkage.

I can never seem to resist trying for a better mousetrap with this connection typology but I really should know better by now. We've probably been through this here half a dozen times since I've been paying attention and we never seem to arrive at a fully awesome connection other than the Simpson gadget.

Super fancy eruo-timber connections aside, I've come to the conclusion that wood just isn't meant to base cantilever unless it's via a root network.

 

[STrctPono]

If you did decide to just embed the pole in a concrete foundation, any chance you could spec out Creosote treating or even CAC treating for the wood? Not sure if this is residential or commercial.

 

[phamENG]

Other than difficult to core, any shrinkage concern between the pipe and wood, and the base connection?

I would think so. The wood is still going to shrink. I guess it comes down to how the wood shrinks. When looking at a cross section, will it always shrink toward the centroid (meaning the exterior diameter will get smaller and the interior diameter will either stay the same or get smaller) in which case you're either ok or the steel post will split the wood as it shrinks onto it or it will shrink toward a center line of the area drawn between midpoints of a series of lines drawn between faces of the member (so the OD will get smaller and the ID will get bigger) in which case you loose your "grip" on the pipe. I'm leaning toward the latter.

 

[Compositepro]

What about tapering the wood and steel socket like the way a shovel is connected to it handle. It can be a square taper. Tapers are very good at producing tight joints.

 

[r13]

Yeah, I would agree the latter be the concern, just not sure, so asked.

 

[azcats]

Taper idea is slick. Can leave open at bottom for drainage. Self correcting for shrinkage. Totally flexible on aesthetics.

 

[BridgeSmith]

...fins look nice but I forsee someone walking into them or tripping over them.

That's definitely something to consider, depending on the anticipated proximity of foot traffic to the post.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[phamENG]

Last time I looked at the Simpson moment base they only went up to 6x6 - looks like they added the 8x8 this past summer.

I'd say your best bet is to use the Simpson base and fake the appearance. Just weld 4 steel plates together in a box that'll wrap around the base and have them stand a few inches taller than the Simpson post base so you can put a bolt through to hold it in place. If that's too expensive, use wood trim to hide it (the wood trim can be replaced on the cheap every few years as it gets beat up).

 

[r13]

I probably would just water/moisture proof the bottom of the pole and insert into the concrete pier. Then provide nice looking removable fittings and sealant to cover the pier-pole interface.

 

[BridgeSmith]

I like the pipe embedded in concrete and up into the post. If the pipe is relatively small (say in the 2" range) there should be plenty enough 'meat' to the surrounding timber to keep it from splitting. If the depth of the hole is kept slightly shallower than projection of the pipe, the bottom of the post will be above the foundation, preventing any issues with the post staying wet.

A similar option would employ 4 rods, rather than a single pipe, in a similar way.

Check out this presentation from the American Wood Council, particularly slide 124, may be of interest.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[KootK]

BridgeSmith's slide 124.

 

[dhengr]

Braves25:
You could dap a couple shear pls. into each face of the 8x8 post, about 18”-24” apart in elevation at the base, with through bolts, depending upon the moments you are dealing with. Then use 4 matching 5.5” wide side pls. welded to a stiff base pl. with A.B’s. into a conc. pier. Drilling a center hole in a long wooden post would seem to be kinda tough to do with any accuracy. Laminating two 4x8’s would allow you to route a center hole for a pipe, and probably laminating the pipe right in place during the post build-up. There are a few wood lam. outfits that laminate posts out of 2x6’s and 2x8’s for post frame building. They can also treat the bottom 6-8’ of the posts for direct embedment.