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12/12 Pitch Fink Truss Bottom Chord Web Joint

12/12 Pitch Fink Truss Bottom Chord Web Joint

12/12 Pitch Fink Truss Bottom Chord Web Joint

(OP)
I'm currently looking at a fink truss with a 12/12 pitch and I have a question about the joint below:



I'm trying to determine if it makes more sense to orient the plate at this joint rotated 90 degrees for high pitch trusses 10/12 thru 12/12.

Does anyone have any pictures of this type of common joint where the plate is rotated 90 degrees. Normally the plate slots run parallel to the bottom chord for low pitch trusses.

RE: 12/12 Pitch Fink Truss Bottom Chord Web Joint

(OP)
The configuration I'm suggesting is shown below:

RE: 12/12 Pitch Fink Truss Bottom Chord Web Joint

Do the work points of the second joint you show line up? As long as the CL of all the members intersect at the joint, I don't see why you couldn't have the plate oriented however you want to accommodate the members.

RE: 12/12 Pitch Fink Truss Bottom Chord Web Joint

Parallel to the chord is the typical way to place the plate. To do otherwise is to risk confusing the minimum wage guy placing the plates on the truss.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

RE: 12/12 Pitch Fink Truss Bottom Chord Web Joint

As long as you get the square inches you need on each piece, what difference does it make?

I can't figure out what you're trying to accomplish...

RE: 12/12 Pitch Fink Truss Bottom Chord Web Joint

(OP)
If the forces on the truss are large and you are wanting to plate the truss with the slots parallel to the horizontal and the plate manufacturer only supplies plates where "h" is never greater than "l", then you end up with a geometry problem.

Perhaps the diagram below clarifies what I'm getting at. Is Option C a possibility from a manufacturing standpoint and plate availability?



RE: 12/12 Pitch Fink Truss Bottom Chord Web Joint

Option "A" wastes plate width. A 6X6 plate would hold roughly the same amount. (In the webs, anyway)

Option "B" would be the most likely that you would see on a truss design.

Option "C" - Plates that are taller than they are wide are all but unheard of.


Forces in common trusses usually aren't that large on residential projects. You won't see many 6x8 plates on web joints. (Pitch breaks joints are another matter entirely)

RE: 12/12 Pitch Fink Truss Bottom Chord Web Joint

(OP)
Your right on most trusses that I'm testing in the calculator at standard loads (ie. 30 psf snow load, 10 TCDL, 10 BCDL) this truss plate rarely gets above a 3x4 or 4x4 plate. However, when I put some large loads on the bottom chord this joint becomes an issue. In particular the tension perpendicular to the grain of the bottom chord requires that the plate extends past the centerline of the bottom chord (ANSI TPI 1-2007 Sec. 7.5.3.3).

RE: 12/12 Pitch Fink Truss Bottom Chord Web Joint

Or they can just single cut any webs over an 45 degree to the chord.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

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