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Structural Adhesives

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I'm re-habbing some timber roof trusses (bottom and top chords 2x6 w/2x4
diagonals).  The trusses have sagged mightily since they were erected 'way
back in the '70's, or thereabouts.  They were *not* designed.  Except for a
few trusses where 1x6 T & G was used for some of the diagonals, the members
calc out okay.  But the connections are woefully inadequate -- for example
4-20d nails each side (thru a 2x6 splice block) of the mid-span bottom
chord splice --  Yes, "mid-span bottom chord splice".    Calculated maximum
tension is on the order of 2500 pounds.  Roof and ceiling sheathing are 1x6
T&G.

Calculated DL + LL deflection is on the order of 3/4".  Actual DL
deflection is closer to 4".  The owner (a church) jury rigged some support
beams and columns near midspan back in the early 80's.  That's what has
kept the whole thing from coming down.

To the business at hand...  Does anyone have any specific experience with
the long-term effectiveness of structural adhesives?  I like the spec for
Surebond, SB-400, but I don't have any information about how it will do on
the long-haul.  For example, our attic spaces here in Florida get awfully
hot, even when they're well-ventilated.

I'd like to use plywood gussets, with enough nails to handle the dead load,
using the adhesive to handle the dead and wind loads.

'Will appreciate input from you timber design folks.

Thank you,
 
Fountain E. Conner, P.E.
1724 Beaver Pond Rd.
Gulf Breeze, Fl. 32561
   Phone 850-932-5547
   Fax      850-934-1916