On Dec 24, 9:43*am, Wayne Whitney wrote:
On 2008-12-24, BobK207 wrote:

You could also use a Senco 16 gage 7/16" crown stapler w/ 2"
staples. * And staple the crap out of the plywood gussets. *Based on
some strength & stiffness tests I did .......... * I figured two
staples have "about" the same capacity as one 10d nail.

Hi Bob,

I've always wondered about staples, does their shear strength differ
in the two direction, parallel to the crown and perpendicular to the
crown?

Thanks, Wayne

The tests I did were with plywood (1/2 - 3/4) stapled to a 2x4
flatwise as the "receiving" member.

The staples were Senco 16 gage 7/16" crown fired from an M2 stapler.

Samples made with clusters of 5 staples were tested & yielded about
250 lbs per staple peak load.
Based on load vs deflection (deflections at peak load were quite
large) I chose to use 50bs, where deflection was well below 1/16" as
a "design load"

For long staples (2") that resulted in 1 1/4" or more staple
engagement, fastener withdrawal did not occur.
The staples remained in the receiving member and "mushed over / pulled
through" the plywood

For shorter staples, that resulted in less than 1" staple engage,
staple withdrawal occurred and peak loads were lower.

Staple orientation seemed to have an effect on deflection at peak
strength but not peak strength.

The reason I like staples is that they don't damage the receiving
member as much as larger nails and (imo) they can approach the
behavior of factory installed truss plates better than nailed
connections.

People tend to focus on strength of a connection but timber
connections have both strength and stiffness characteristics and
depending on the situation, one can be more important than the other.

cheers
Bob