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Strength of old truss plates
5

Strength of old truss plates

Strength of old truss plates

(OP)
Trying to evaluate the resistance values of truss plates in a residential roof built in the 1960's.  There are two teeth per an area of approximately 1in x 1.5in.  Teeth approx 5/8inch deep. 18gage plates. Can't find any values for this plate.  Would using the resistance values of current Mitek plates be acceptable?

RE: Strength of old truss plates

Probably not.  Truss plates have changed a lot since then.  I'd call Mitek and ask if their engineers have any information on old plates.

RE: Strength of old truss plates

Are you sure they are Mitek??  They started out as Molenpah (SP??) Engineering back in the '60s There was also Gang-Nail and Lumbermate!!

Look carefully at the plate - you might find a name - but I doubt it - most of us tried to "hide" back then!!

RE: Strength of old truss plates

2
The current values would not apply to the 1960 plates.

Here is a short? list of some of the plates in the 1960's
Anchor Lock, Anchor Lock of Florida
Dura-Plate, Duralite of Ohio, Inc.
Trusset Plate, Empire Roof Trusses
Gang-Nail, Gang-Nail Sales Co.
H-Brace, H-Brace, Inc.
Hydro-Nail, Hydro Air Engineering
Hercules Truss Plate, International Truss Plate
Penhurst Connector, Penhurst Machine Co.
Ronel Barbgrip, Ronel Corporation
Sanford Gri-P-late, Sanford Truss, Inc.
Templin Truss-Lock, Templin Associates
Tim-Plate, Timber Fabrication
Gismo Gusset, Truss Prefab, Inc.
Truss-O-Matic, Truss-O-Matic, Inc.
Tru-Raf, Truss Connectors of America, Inc.

Not sure how you would go about finding the plate you have and its original values.

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: Strength of old truss plates

Maybe a 100 lbs/sq in....  Just a thought - but no guarantees...

Newer designs often exceed 200 psi

RE: Strength of old truss plates

The plates you have are significantly different than current plates as others have noted. The 5/8" teeth are a give-away. For current plates with 1/4" or 3/16", capacity is directly related to tooth embedment. Loss of embedment drops the capacity quickly.

With 5/8" embedment, the capacity is likely higher, but that depends also on tooth density.

Most truss plate capacities are empirical anyway, so you'll need some tables from the mfr. Search as others have noted.

RE: Strength of old truss plates

But with 5/8'' embedment - you lower the remaining "plate" steel resulting in less shear and tension capacity. Designing a truss plate was always an exercise in compromise. That's why we usually had 3 or 4 different "types" to be used as required.

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