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Timber Truss Gusset Plate

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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