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Split Rings

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I would be very careful designing using split ring connectors.  I have seen 
several failures of wood trusses that were approximately 30 years old where 
the split ring sheared the wood off the ends of highly loaded diagonal 
members.  (Secondary failures gave the impression of failure due to 
twisting of the joints, but the twisting was the result of failure of one 
of the trusses having the split ring shear off the end of a diagonal.)  The 
trusses were not overloaded, not subjected to snow loads (Tucson, Arizona), 
and occurred when no live load was present.  Analysis of the truss under the 
code in existence when it was designed and the then current code showed that 
the truss should have been adequate for dead plus live loads.

Dismantling a truss that had not failed revealed a plug of wood remaining 
within a split ring, i.e., separated from the wood member, therefore that 
area did not contribute to the strength of the connection.

Were I to design a split ring connection, I would use only 1/2 of the 
tabulated values in the NDS (if I would use that much).

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Keith De Lapp wrote:

. > I have just completed a design for a truss using split rings.  The design 
. > info I obtained from the NDS.  Can someone out there tell me why, when I 
. > do a search at ICBO, I do not find a report?

. > Also, I read somewhere that UBC requires that split rings be designed 
. > using a factor of four for the allowable load.  When I look through the 
. > UBC, I see no mention of split rings or shear plates in the timber 
. > fastener section.

. > I also read that Cleveland Steel is the "only" manufacturer of split 
. > rings in the country, and they have no info available on their web site.

. > Anybody got their ears on out there that can offer a word or two of
. > assistance.

. > Thanks

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