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Deflection due to splice slippage

Deflection due to splice slippage

Deflection due to splice slippage

(OP)
Deflection is related to curvature right?  I need to calculate the deflection of a plated wood roof truss if the bottom chord splice slipped 1/8".  Any ideas?

RE: Deflection due to splice slippage

draw it

RE: Deflection due to splice slippage

1) If the bottom chord splice slipped 1/8" than the splice has failed. I would jack up the truss till the gap is closed and place a add-on to one face and nail for the maximum tension force.
2) If the truss was built with a 1/8" gap, under normal loads (as all the trusses were built on the same table) it will have no addition deflection. For this, I would recommend to wedge/shim the gap or add an add-on to one face for the code maximum wind condition.
As for additional deflection due to a increase in lenght of the bottom chord of 1/8", there will be only be a non-measurable amount due to the tension force in the bottom chord holding the truss up.

Garth Dreger PE
AZ Phoenix area

RE: Deflection due to splice slippage

I do not dispute what woodman88 has said, but the question asked is a matter of straightforward geometry.

If the splice has slipped 1/8", the angle change (call it φ) in the truss at that point is 1/(8*D) where D is the depth of truss.  

If it happened at midspan, the rotation at each end is φ/2, so the deflection at midspan is (L/2)*φ/2.  

If it happened a distance 'a' from the left support, the rotation at the left support is φ(L-a)/L, so the deflection at the splice is φ(L-a)a/L.

In other words, you can treat a concentrated angle change as a point load on a beam.

BA

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