8x8 post fixed base
8x8 post fixed base
(OP)
I can't recall to have ever fixed the base of wood post. I have a situation where I might have to do that. I couldn't find an appropriate simpson base anchor for that. Is a custom built base plate the way to go? I am thinking of a steel base plate with welded HSS to fit the 8x8 in.






RE: 8x8 post fixed base
Or trying to minimize the sideways movement of the bottom of the post by anchoring the steel widget down to the underlaying concrete (with a vertical through-bolt perhaps); so that you want the steel widget to be able to be bolted firmly to the wood post? (That is, through bolt holds the steel to the concrete by resisting shear, and the secondary bolts hold the steel to the wood by resisting pull-out?
RE: 8x8 post fixed base
A company call Sturdi-bracket makes something they say will transfer "some" moment. Google that. Be careful - it is capable in one direction only.
An HSS bracket might work - sort of. If there is any "wiggle" in the timber to HSS - then you will lose some capacity.
RE: 8x8 post fixed base
htt
These post bases feature 1" standoff height above concrete floors, code-required when supporting permanent structures that are exposed to the weather or water splash, or in basements. They reduce the potential for decay at post and column ends.
RE: 8x8 post fixed base
RE: 8x8 post fixed base
But I do need a base that works in uplift as well as shear in both directions. I should be able to find that in Simposn for 8x8, I think.
RE: 8x8 post fixed base
RE: 8x8 post fixed base
And being in that industry - seems to work....
RE: 8x8 post fixed base
RE: 8x8 post fixed base
Mike McCann
MMC Engineering
RE: 8x8 post fixed base
So, you'd need a short section of HSS with an inside dimension of 7.5 x 7.5 inches, then weld that to a backing plate (of 1/4 or 3/8 plate ?) 8.5 x 8.5 with a cheap, easy fillet fillet.
To resist pullout, use 2x 1/2 bolts through the HSS.
Alt: Bend a 1/4 or 5/16 thick plate 8 inches wide into a U with inside width of 7.5 inches. Use 1, 2, or 4 anchor bolts into the slab/foundation on the bottom of the "U", and clamp the two walls of the "U" into the wood post with through bolts.
RE: 8x8 post fixed base
RE: 8x8 post fixed base
RE: 8x8 post fixed base
Hokie's comment regarding shrinkage is valid. A bigger problem is the installation. We need the bolts to be snug to the wood in order to resist the moment. The bolt holes will almost always be overdrilled- killing the fixity.
RE: 8x8 post fixed base
For higher load conditions, I would use two vertical plates welded together and to a base plate. Designed for the moment required. Bolt the post to the each plate with plate washers. Design the wood connection on perpendicular compression of wood against the plate washer to resist the moment in each direction. Using the bolts only in tension.
This would of course be too visual for most architects or owners.
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: 8x8 post fixed base
RE: 8x8 post fixed base
RE: 8x8 post fixed base
How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban
RE: 8x8 post fixed base
Cross grain shrinkage. Teguci's solution goes a long way toward dealing with the loosening of the connection due to shrinkage of the timber.
RE: 8x8 post fixed base
nice detail. The spacer at the bottom elevates the wood and avoids the rounded fillet...
Dik
RE: 8x8 post fixed base
I don't mind teguci, I just wouldn't want to be the poor guy that has to install this connection.
How could you do anything so vicious? It was easy my dear, don't forget I spent two years as a building contractor. - Priscilla Presley & Ricardo Montalban
RE: 8x8 post fixed base
With Teguci's detail, you can have the holes in the steel made to match the screw shank. Predrill a bit smaller and run in the screws. Done.
RE: 8x8 post fixed base
The only issue I have is that it seems to me that he has detailed half the screws and nuts and anchor bolts to be left handed threads, and they may be hard to come by. And, most certainly will confuse the hell out of the contractor's workers.