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Re: Timber Truss Gusset Plate

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I would agree that the joint is in equilibrium, and
that the axial member forces are resolved into their
respective vert and horiz components.  So, no, there
should be no/minor perp-to-grain forces on the bottom
chord for example...  I would then to think that the
first quarter undergrad lectures in Statics should be
true.  Otherwise, why would the method of joints be
David Topete, PE

--- Rich Lewis <sea(--nospam--at)> wrote:

> I am designing a timber truss using Parallam lumber.
>  The panel points
> are connected with steel side plates and bolts.
> I have a question as to how I see the bolted
> connection designed.  I
> analyzed the truss with a frame analysis program and
> I have all the
> member forces for various load combinations.  I
> modeled the web members
> as pinned ends and the top and bottom chords as
> continuous members.  As
> I see the joint connection design I design the
> number of bolts based on
> the member forces.  The forces in the members are
> primarily axial forces
> so the bolts are designed based on parallel to grain
> values.  The top
> and bottom chords have some minor shear due to the
> continuous modeling.
> Let me see if I can explain this further.  I will
> illustrate this with a
> specific joint, a bottom panel joint that has the
> bottom chord
> horizontal on either side, a diagonal going up to
> the top chord and a
> vertical going up to the top chord.  The force from
> the diagonal goes
> into the steel plate.  The vertical component of the
> force is resisted
> by the vertical web and the horizontal component is
> resisted by the
> bottom chords.  The force is distributed to these
> members through the
> gusset plate.  As I see it I don't have any
> perpendicular to grain
> forces in the bottom chord (except the minor shear
> forces) or the
> diagonal or the vertical.
> I need a sounding board to bounce my thoughts off
> of.  Am I looking at
> this correctly?  Would this plate put a twisting
> force in the joint that
> will put perpendicular to grain loading in the
> bottom chord?  Would
> joint equilibrium negate this possibility?
> Thanks for your help.
> Rich Lewis
> Lewis Engineering

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