strength of threaded rod?

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The through bolt for wood framing is going to hold the joint from coming apart but by itself may allow some shear movement, making the joint and the rod weak in the shear direction.

Some polyurethane adhesive or supplemental framing connectors that hold in the shear direction could be needed to let the through bolt do its job fully. In the old days it would be a mortise and tenon connection with the peg doing what the through bolt is proposed for.
 
S'mise said:
That's a greateat point. Can I assume threaded rod shear is essentially the same? That is, the weak point in either being the narrowest part of the thread?

Is tensile strength higher in a bolt since the head of a bolt would be stronger than a nut?
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I'll speak to a particular application of threaded rods, bolting hydraulic valves to subplates or manifolds. The industry has found that (the very rare) fastener failures occur in the threaded portion. Typical nuts are not used; occasionally, with fully threaded attachment, a long nut is. Note here that these fasteners "exceed Grade 8 specifications", and are sometimes (incorrectly, there is no such thing) called "Grade 9".

The issue is that fastener stretch (elastic region is ALWAYS assumed) depends on the PSI loading and Young's modulus of the material. Since the cross sectional area is smaller for a longer length, less load is required to open the joint, even well below yield.

So what? A 36" long all-thread and a 36" long rod with threaded ends will have the "same" load capacity, but the all-thread will stretch more with the same load. If the rod was field (cut) threaded, it will be weakest at the thread/rod point. If it is all-thread, it is almost certainly rolled thread, and will be handle more tensile load than a cut thread rod.

When we hang by all-thread, there is no shear to consider. So, IMHO, all-thread will be STRONGER than equivalent material field threaded rod, but will stretch more ... who cares, we position loaded.

Slightly off topic, but food for thought.
 
Sounds to me like sagging of the horizontal members will be a factor WAY before any shear break. Or some other damage to the horizontal. You don't say what the horizontal material is.

The problem with internet forums is lack of communication — all the factors presented so an evaluation can be suggested. Someone said see or talk to an engineer. You think an engineer would give an answer based on what this forum has been told? I'm sure everyone would like to help, but there's no way given the scant info.
 
S'mise said:
No bolts.
5/8 threaded rod going through vertical wood timbers (10ft span) with flat washers and nuts on either side holding 2x10 horizontal planks on each side of them.

Trying to get a ballpark idea of the downward force it can withstand before shearing.

I assume If load is placed in center the rod can safely hold 2936lbs (1468 x 2).

....Or, perhaps x4 as there's 4 contact points.
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I think the properties of the wood have a dominant role here, as well as the design of the joint itself (single shear vs. double shear, etc.).

The following document has some info about this and there is much more information available out there on this subject:

https://www.google.com/url?sa=t&sou...FjAAegQIARAB&usg=AOvVaw1wFtHoU2Id3d8tSXpjEmYf
 
S'mise said:
No bolts.
5/8 threaded rod going through vertical wood timbers (10ft span) with flat washers and nuts on either side holding 2x10 horizontal planks on each side of them.

Trying to get a ballpark idea of the downward force it can withstand before shearing.

I assume If load is placed in center the rod can safely hold 2936lbs (1468 x 2).

....Or, perhaps x4 as there's 4 contact points.
Click to expand...

This sounds like a pier or walkway. Maybe a deck?

Watcha buildin?
 
oldsparky52 said:
This sounds like a pier or walkway. Maybe a deck?

Watcha buildin?
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A tree house. Threaded rod 5/8" goes through tree and is sleeved with 1/2" black pipe over it (on the outside) for additional strength.
the horizontal planks don't actually attach to rod, but rather sit on the top of it (ride) to accommodate tree sway.

I don't want to monopolize an off subject here, but load limits of threaded rod seemed relevant to ask here. I'm just using it in an unconventional way.

I was hoping there was a go-to reference that was widely used and trusted, but info on the web is a bit confusing and very inconsistent.

I realize this is a difficult to answer question because of the variables involved.

I just want to know approximately how much downward weight can a 5/8" allthread rod can safely hold.
I don't require an exact answer by an engineer, merely a ballpark figure that I plan to stay well under.

1468lbs on each point of support is the best conservative answer so far.
 
190912-0634 EDT

S'mise:

This thread is now an illustration of not asking the correct question. On any problem you want to solve it is important to try to figure out the correct question or questions to ask.

Shear may not be your problem. Bending may be.

You should not use threaded rod. Rather a solid round rod is better, but then the same amount of material (weight) used in a tube would make a larger diameter and thus stronger in bending.

Since you are going put a sleeve over the threaded rod in the tree simply extend this out as your mechanical support.

In bending, which is possibly your dominate factor, a cantilevered beam stiffness or strength is related to both shear and tension. This gets you into the moment of inertia of the shape, the why of I beams, and factors that relate to the square of radius.

You actually have a very complex problem to solve. But you want a simple answer.

3/4" galvanized water pipe, or stainless might be good.

.
 
Fulthrotl said:
well, shoot. you shoulda just said so.

my brother in law has this airbnb treehouse in julian.
it uses a mounting system that allows for tree growth and movement.
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I'm trying to keep the conversation on threaded rod/electrical related. Perhaps this should be moved to fireside chat?

That is a very cool house, although it looks like just the deck portion is held up by trees.

They do sell anchoring bolts designed for this, but they are extremely expensive. My design isn't as robust but it will be supported by 4 trees so weight is divided amongst 8 points. Two trees have 5/8 rod, and two have 3/4 rod through them.

This project is already underway but I'm trying to get an idea of load limits. The load will be between 2500 and 3klb.
 
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A few thoughts, in no particular order:

1. The compressive strength of the wood is going to be a lot less than the shear of the rod.
2. Use a high grade rod, not you typical hardware store crap.
3. Why not go 3/4, maybe even 1"
4. these are the best. GL's. Are they the expensive ones you mentioned? https://treehouses.com/joomla/index.php/construction/garnier-limb
5. I might go 1500 pounds per bolt, or on each side if its set up that way.
 
electrofelon said:
The issue would be copmressive failure of the wood, A larger hole would result in more bearing surface. I dont see general overall weakening of the tree trunk as an issue.
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Not the tree trunk, the wood joists I'm assuming he is using, like most tree houses
 
Hv&Lv said:
Not the tree trunk, the wood joists I'm assuming he is using, like most tree houses
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OP said "the horizontal planks don't actually attach to rod, but rather sit on the top of it (ride) to accommodate tree sway" Even if they were bolted on, I think the increased bearing surface would far outweigh the risk of a slightly larger hole resulting in catastrophic failure of the joist.
 
electrofelon said:
OP said "the horizontal planks don't actually attach to rod, but rather sit on the top of it (ride) to accommodate tree sway" Even if they were bolted on, I think the increased bearing surface would far outweigh the risk of a slightly larger hole resulting in catastrophic failure of the joist.
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I see that now...
I jumped to conclusions. :ashamed1:
I see so many trying to build decks and treehouses with Sheetrock screws, and even deck screws with minimal penetration. Also drilling huge holes for additional items like swings and storage racks that weaken the structure..
 
electrofelon said:
A few thoughts, in no particular order:

1. The compressive strength of the wood is going to be a lot less than the shear of the rod.
2. Use a high grade rod, not you typical hardware store crap.
3. Why not go 3/4, maybe even 1"
4. these are the best. GL's. Are they the expensive ones you mentioned? https://treehouses.com/joomla/index.php/construction/garnier-limb
5. I might go 1500 pounds per bolt, or on each side if its set up that way.
Click to expand...

Good points. Especially the first one. I'm usung 2x10 x12 pt Douglas fir on each side. From what I've read they'll support an open span of about1200lbs a piece. So my threaded rod will likely be stronger than the 2400lb limit on each side.

Yes, Garnier limb or Tab bolts are extremely expensive, this is a cheap alternative capitalizing on the fact that load is divided between 4 trees.

I've already got this thing mostly built. Just having some second thoughts about loading.

As far as threaded rod: Although I didn't get a definitive answer, I feel confident it will withstand the loads it should see. That is, it was answered to my satisfaction.

​​​​​Thank you all for the great advice, I have learned a few things.

I will open another thread under fireside chat and post some pictures if anyone is interested.

I feel this is getting too off topic to continue here.

Regards
 
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