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Re: wood truss and glue- sorry second try

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Mark,

I concur with Dennis and Jeff. Just too many unknowns about the bonding of
the adhesive, etc.

Bruce Pooley, P.E.
Timber Design
3447 S. Newland Court
Lakewood, CO 80227
HB
----- Original Message ----- 
From: "Jeffrey Fertich" <civilben1968(--nospam--at)hotmail.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Sunday, June 27, 2004 12:12 PM
Subject: RE: wood truss and glue- sorry second try


> Mark:
>
> I know your questions here are to solicit good suggestions on how to get
> your job done, to follow Dennis's gut feeling, mine is to run don't walk
> from this.  I run into so many contractors with the "I glued and screwed
it,
> it has to work" attitude.  First, what plywood did he use? was the main
> members dry enough to not shrink, was it clamped properly?  are the
plywood
> gussests big enough.  I have ususally found the the amount of plywood and
> labor required quickly justifies the the use of pre-built, pre-engineered
> wood trusses.  Sorry that this is not helpful I just have to rant about
the
> contractor with the "i don't need no stinkin engineer" attutude leaving
you
> to bless this mess when you would probally never have designed it the way
he
> built it.
>
> Jeff Fertich, PE
> Structural Engineering Resources, LLC
> Gettysburg, PA
>
> >From: "Dennis Wish" <dennis.wish(--nospam--at)verizon.net>
> >Reply-To: <seaint(--nospam--at)seaint.org>
> >To: <seaint(--nospam--at)seaint.org>
> >Subject: RE: wood truss and glue- sorry second try
> >Date: Sat, 26 Jun 2004 18:39:28 -0700
> >
> >Mark,
> >I can't respond to this with any knowledge or experience in the creation
of
> >a site built wood truss using glued gusset plates and nails. However, I
> >would like to comment from a Professional "Gut" feeling and see how far
off
> >track I am.
> >Nailed plates (or even pressed plates) are intended to allow some
rotation
> >at the joints. Even though the chords may be continuous, the connection
at
> >the struts allows for bending and the nodes have been historically
> >considered pinned. When applying a glued gusset plate my 'gut' tells me
> >that you reinforce the rigidity of the node and change the distribution
of
> >forces on the truss members. More to the point, the nails have no value
> >until the more rigid glued connection fails. If the glue separate or the
> >ply of the plywood gusset splits, the load to the nails could cause the
> >truss to fail without warning.
> >
> >I've seen site built trusses, but most of them are simply nailed, bolted
or
> >in the Midwest (more than out West) mechanical connectors such as shear
> >plates are used.
> >
> >FWIW, I know of Gorilla Glue as a recommendation used to repair fine
> >instruments because of its ability to resist changes in humidity and to
> >maintain its strength over long periods of time. The only difficulty I
have
> >heard (about most glues) is when used on woods that have an oily residue
> >such as Rosewood.
> >
> >Now that I let out my ignorance of site-built trusses, I would be happy
to
> >hear how far off my 'gut' feeling is.
> >
> >Regards,
> >Dennis
> >
> >
> >Dennis S. Wish, PE
> >
> >
> >California Professional Engineer
> >
> >Structural Engineering Consultant
> >
> >dennis.wish(--nospam--at)verizon.net
> >
> >http://www.structuralist.net
> >
> >
> >
> >
> >-----Original Message-----
> >From: Mark Miller [mailto:milm(--nospam--at)chemeketa.edu]
> >Sent: Thursday, June 24, 2004 11:42 AM
> >To: seaint(--nospam--at)seaint.org
> >Subject: wood truss and glue- sorry second try
> >
> >Hello-
> >
> >I have a client that has built some wood roof trusses (normally I try to
> >avoid projects like this, but long storyâ?¦..). The trusses look very
> >reasonable in their construction. I will have to analyze them for
strength
> >and deflection, but before I put the time into doing this I was concerned
> >with the way the plywood gussets were glued to the truss members. They
used
> >Gorilla Glue and nails to hold the joint tight while the glue cured. I
was
> >concerned with how Gorilla Glue (one part polyurethane glue) compared
with
> >the resorcinol glue that we have used in the past. I have contacted the
> >makers of Gorilla Glue and they were very helpful and pointed me to some
> >tests done by the USDA Forest Service Forest Products Lab. The shear
> >strength, in these tests, looked as good or better than resorcinol for
use
> >on doug fir. I am still concerned with the long term performance and
> >performance in a fire (high temp). This is in Oregon and under the UBC.
> >
> >Does anyone have experience with this?
> >
> >What do you think?
> >
> >
> >
> >Thanks for your consideration.
> >
> >Mark Miller, PE
> >
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> >
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