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Question About Timber Post Connection To Concrete Pier

Started by Believer, October 29, 2012, 08:53:10 AM

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Believer

I would like to build a timber entrance to my property--this is a road entrance.  I'm inexperienced, so you know.  Basically I'm thinking of constructing an interesting truss or bent, like a sling brace, and erecting it on a couple substantial concrete piers.  It will be about 18' wide and high enough for large trucks to go under.  I want large timbers for visual interest.  I hope someone can inform me how I connect the post to the pier.  Another question I have is whether I need any bracing perpendicular to the bent.

Jim_Rogers

There are many ways to secure the post to the concrete.

Most will require you to embed something into the wet concrete as it's being poured and hold the wood up off the concrete to prevent the moisture in the concrete from wicking up into the bottom of your posts.

Bracing will all depend on your exact design and wind exposer.

Small timbers without a large "sign type" beam may allow the wind to pass right through.
But a large sign type thing would act like a sail and catch the wind, which could require a stronger base unit.

Until you show the exact design it's very hard to say.

There have been many posts here about concrete to wood connections. You should/could do a search and see if anything that is already here would help you to design your entrance way.

I would also suggest that you have your finial design reviewed by a timber frame structural engineer for safety.
If you need help finding one let me know I know many of them who can help you.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

grweldon

As Jim mentioned, without knowing the timber size it's hard to say.  I poured some footings for my barn this weekend and embeded some Simpson post attachments into them.  I can post a picture but there are probably many already on the forum.  I'm only using 4 x 6s for my support posts so the connectors are only 3.5 wide, but there are ways to use this type of connector on larger timbers if you determine the embedding method is strong enough for your use.
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Believer

I was mainly trying to get some advice on the connection at the base of the post.  I'll probably be using 12"x12" timbers.  Let's say I embed a 4"x5" steel tube that's 3 feet exposed above the concrete footing.  How do I get the post attached to it?  Thanks.

Jim_Rogers

I would think that you'd want as much in the concrete as you would have in the post. But I'm not an engineer and I don't know for sure if that would be the case.

You should consult an engineer and get some correct answers.
Any advice here could be 100% wrong and weaken the structure instead of making it stronger.

There are many ways to do it and you need to be very site specific with your information when you discuss it with an engineer.

He will need to know the site and frame specific information. Such as but not limited to, type of wood, overall weight of structure, span between post, overall height, wind load, wind exposure (for example is it totally out in the open or sheltered by strong hardwood trees), size of footings, and specs on concrete and rebar.
If you don't know these things then he can suggest to you how to find them or advise you what to use.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Satamax

Hi everybody.

Well, concrete piers are à concern to me.  I mean, i'd like to make myself a building like this.



On the hangar side, i i could avoid the slab for the moment, that would be cheaper to build. So i thought concrete piers. But i realy like the old style, big block with a square hole in it, where you slide the post in. so it helps bracing. Usualy the timber is protected by tar. Thought, i don't know how durable this is.

In france, for farm hangars, they're often on piers that way.




I wonder how long it would last. Any better way, if possible not using metal?

Thanks a lot.

Max.
French CD4 sawmill. Latil TL 73. Self moving hydraulic crane. Iveco daily 4x4 lwb dead as of 06/2020. Replaced by a Brimont TL80 CSA.

Rooster

Quote from: Believer on November 01, 2012, 08:37:19 AM
I was mainly trying to get some advice on the connection at the base of the post.  I'll probably be using 12"x12" timbers.  Let's say I embed a 4"x5" steel tube that's 3 feet exposed above the concrete footing.  How do I get the post attached to it?  Thanks.

¾ in. x 12 in. x 60 in. Steel knife-plate perpendicular to the bent... inbedded into a 24 in. Dia concrete column.  Post secured with 1 in. through bolts...maybe counter sunk with plugs...

I vote for a modified hammer-beam truss...more head-room down the middle without being super tall...plus a nice spot near the top to hang the farm name sign.

Good Luck,

Rooster



  

  

 
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       and new barns are a reminder that I am not so young."
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Jay C. White Cloud

Hi Everyone,

Here is my "two cents,"  I have already voiced not liking to use concrete too often but recently, I have helped facilitated a few frames that incorporated it in a way I can live with.  Here is an example:

This is a wedding arch made of cherry posts and black walnut lintel sitting on granite glacial erratic plinth stones.  The young man in the photo is a dear friend and student of mine.  He operates "Wild Wood Timber Works," in Thetford, Vermont.  He made this beautiful piece and was married under it this summer.


Model of frame.


This is a close up of the plinth connection.  You can configure this in many different formats depending on the demands of the individual architecture.


The close up of the plinth connection demonstrates a method that we have used on several buildings this year.  Depending of the demands and/or engineering specifications, we size a concrete column below grade to match the architectural demands.  That column ends at grade level.  Then the stone plinth is positioned on top of that.  The plinth is drilled and position over the steel rod that is secured in the concrete per industry standard.  Then the post is place on that assembly and secured accordingly.  This method allows for a mix of traditional methodology while still meeting the modern demands often found in engineering assessments for a project.

It seems complicated, but in reality, is very easy to do.  The photo of the "wedding arch" is of an instillation that is attached to 20 mm (3/4") PT plywood shear plate and bolted to the plywood with threaded rod.  Once in place, it was extremely stable and now is sitting in a sculpture garden in Woodstock, Vermont.  It can be easily move and/or place on concrete column for a permanent installation.  ;)

Regards,


Jay
"To posses an open mind, is to hold a key to many doors, and the ability to created doors where there were none before."

"When it is all said and done, they will have said they did it themselves."-teams response under a good leader.

Brian_Weekley

Looks nice, but I'd be very concerned about water infiltration and post rot--especially when exposed to the environment.  What do you do to protect against that?
e aho laula

Jay C. White Cloud

Hello Brian,

Those are legitimate concerns, and I have seem some poor facsimile of this type of foundation that did not weather well do to improper application/implementation.  When employed correctly, this type of foundation has lasted centuries, (in a few cases millenia.) 

The stone, by it's natural shape drains water quickly.  In the past, when I have done similar art installations, (and proper implementation of this foundation technique,) oiling the structure once or twice a year, was all that was needed to keep it in good shape.  Even neglected one's lasted for well over 20 years with no intervention at all.

When applied to architecture, they are well under the "drip line," of the structure, for the most part, thereby removing the primary concern for water damage. 

Regards,

Jay

"To posses an open mind, is to hold a key to many doors, and the ability to created doors where there were none before."

"When it is all said and done, they will have said they did it themselves."-teams response under a good leader.

timberwrestler

Quote from: Brian_Weekley on November 19, 2012, 05:52:31 PM
Looks nice, but I'd be very concerned about water infiltration and post rot--especially when exposed to the environment.  What do you do to protect against that?

And cherry and walnut are naturally rot resistant
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Brian_Weekley

Ahh, I think I was looking at JC's drawing incorrectly.  It was unclear to me that the post is scribed to the top of the rock.  For some reason I thought the post was sitting in hole carved into the rock! In which case, water would be a problem--cherry, or not.  Makes more sense now and a lot easier to do, eh?
e aho laula

Jay C. White Cloud

Hello Brain, 

;D Now you got it!  Some times, in certain circumstances, we will carve a mortise into the rock, (usually ledge and mortise one rock into another, and them maybe a post into the rock, instead of scribe fitting.  This however is done where water won't be a issue, and/or we carve in drainage ports into the plinth to facilitate dryout.

Regards,

Jay
"To posses an open mind, is to hold a key to many doors, and the ability to created doors where there were none before."

"When it is all said and done, they will have said they did it themselves."-teams response under a good leader.

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