Split Ring Connector Question NDS 12 2

[driftLimiter]

Hello colleagues.

Today my question is about NDS 12.1.
The code defines a connector unit as "One split ring with its bolt or lag screw in single shear".

I am hoping to use a configuration that includes multiple split rings connecting multiple elements.
The orientation of the connection will ultimately be similar to a "double shear" condition.

Should this be interpreted as: double shear split ring connectors are not allowed? Or....
That whether or not the configuration is in double shear or single shear, the strength of the connection should be based on double shear?

I lean towards the second of the above options. In that I can arrange them back to back and connect multiple plies, but I can only consider the single shearing strength.
I have attached a picture to help illustrate the conditions I am thinking of.

Does anyone have advice for interpreting this line of code?

Many Thanks in Advance.

-DL

 

[DBronson]

driftLimiter:

I think that language comes from the tables used for wood connector design which show values for single shear. If you look a page 2 of the "Design Manual for Teco Timber Connectors" it discusses this. A link to the pdf is:

Link

Multiple connectors on a single bolt are used all the time.


Regards,

DB

 

[dhengr]

DriftLimiter:
Each split ring connector acts in single shear btwn. two wooden members. The middle member must be thick enough so that it will accept split rings on two faces, and so that the split rings can distribute their loads properly. The lag screw for a single split ring btwn. two members, or in your case a bolt through more than two members really doesn’t contribute much to the strength of the joint in comparison to the cap’y of the split rings, they primarily tighten the members together at the faying surfaces so that the split rings can act as intended. The bolts may not even really come into full bearing on the wood hole, if the split rings are installed properly and tightly in their daps.

 

[driftLimiter]

Got it.

Thanks for the helpful responses to Dbronson and dhengr.

I thought as much about the split ring being in single shear.

But dhnegr are you saying that bolt doesn't even really engage in bearing on the split ring?
So checking shear in the bolt is not a limit for these connections...

I suppose this is what the code is implying and what you are saying...

 

[dhengr]

DriftLimiter:
When done properly, the split ring has to be pressed into its circular groove (dap) on both pieces of lumber, something of a wedging fit into the wood groove, and it may actually open up a bit at the split as this fitting/pressing occurs. This is a fairly snug fit and the split ring starts picking up the load without much movement in the joint. The joint doesn’t move enough to really bring the bolt into a crushing bearing in the wooden holes, so we just don’t know how to calc. the bolt’s contrib., if any. Obviously, the lag screw would tend to pick up some of the load immediately, since it is in a tight hole, while the bolt is not in that tight a hole, and must move a bit for bearing on the wood. In any case, each split ring, at its faying surface is treated as if in single shear in that faying surface. I don’t think I’ve ever checked the bolt shear in this case. A joint that is well laid out, fitted and fabricated will allow you to make the assumption that the loads are more evenly distributed btwn. multiple split rings because of the lack of initial joint movement. Split ring connections are tight enough so they sometimes cause splitting problems in the wooden members as they dry and shrink with time.

The shear plate connection is another matter. Their joints tend to have more movement to bring the two halves of the shear plate pair into bearing and shear in their wood grooves. This may allow the bolt to come into bearing in the wood hole, but we still don’t really know how to quantify that very well. The member forces go from the wood to the shear pl. in its groove, in bearing btwn. the two materials; then though the shear pl. to the bolt which is in single shear; and into the other half of the shear pl. pair (the opposite shear pl.) and finally into the other wooden member. So maybe, at best, you could say that some long bolts in these joints are in single shear, several times. This is a bit of a difference, but with a distinction too, since the joints act quite differently than three lapped steel pls. with bolts, where we typically do talk about double shear on the bolts or pins. Draw some free body diagrams, and follow the load paths at each step, and see if that helps clear things up.

These connectors need some wooden beef around them to function properly, that is, fairly thick large wooden members. I’ve used them on large GluLam beams and large timbers. I don’t remember, off hand, if I’ve ever used them on smaller lumber pieces. I don’t have the last couple eds. of the NDS in front of me, and I haven’t really looked at any TECO literature in some time, so you’d have to post copies of specific paragraphs which are still troubling you, for me to add much more..

 

[Ron]

Split ring connectors should take all the shear of the connection. The bolts are used to keep the connectors in place. The bolts should not be considered in the capacity.