Horizontal Reaction from Truss
Horizontal Reaction from Truss
(OP)
Attached is the truss diagram. The existing exterior wall is 2x6 studs @ 16" o.c. w/ plywood sheathing. What is the best way to handle the horizontal reaction? Thanks.
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Horizontal Reaction from Truss
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RE: Horizontal Reaction from Truss
If I remember correctly, the TPI limits are 0.75" under LL and 1.25" under total load. Your truss is goofy in the middle. It seems to be made in halves not connected at the bottom and has some extraneous horizontal webbing. Do you know why?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Horizontal Reaction from Truss
BA
RE: Horizontal Reaction from Truss
RE: Horizontal Reaction from Truss
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RE: Horizontal Reaction from Truss
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Horizontal Reaction from Truss
Didn't run/check the math, but looks like they supplied design forces for field connection at top and bottom chords,
Webs aligned to facilitate field connections..
RE: Horizontal Reaction from Truss
It looks like it covers a fairly long roof (16 trusses total) so if they really want to have it constructed in halves, maybe suggest having a parallel chord girder truss run down the middle with skew hangers to hold the trusses.
RE: Horizontal Reaction from Truss
BA
RE: Horizontal Reaction from Truss
RE: Horizontal Reaction from Truss
BA
RE: Horizontal Reaction from Truss
RE: Horizontal Reaction from Truss
Good article. I have questioned Simpson's engineers on their slotted clip Link
and asked how the wind load on the wall gets into the diaphragm. They could not give me a good answer. Clearly, they are more marketers than building designers.
RE: Horizontal Reaction from Truss
@XR250: frankly, I'm surprised that such a product even made it into production. Even if we didn't care about wall restraint, I'm sure that friction renders is ineffective.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Horizontal Reaction from Truss
There is no way the wall can be constructed to resist large horizontal forces. Perhaps the best solution is to reduce the slope of the bottom chord and tie the trusses together at Joint 'T'. The geometry of the trusses could be adjusted to render the horizontal deflection acceptable.
BA
RE: Horizontal Reaction from Truss
Wondering on truss if, instead of reducing slope on bottom chord, the slope on the top chord was adjusted towards parallel to bottom chord, retaining ridge height at exterior and interior, kinda like two parallel chord trusses, creating a larger moment of Inertia and reducing deflection..... messes with architectural lines though...
photo is confusing to me as it looks like a ceiling at the roof line, but then, why would this discussion be occurring... if this is a second story addition, then the exterior walls at the new trusses are not existing....
RE: Horizontal Reaction from Truss
This is the weirdest scissor truss I've ever seen. As mentioned above there is not connection at joint T, the truss will split apart at this joint.
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RE: Horizontal Reaction from Truss
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Horizontal Reaction from Truss
The horizontal forces at top and bottom are 5240# and 5948# respectively which are to be resisted by a field connection of some sort. The detail of the connection is not provided.
BA
RE: Horizontal Reaction from Truss
Otherwise, it might just get toenailed together :>
RE: Horizontal Reaction from Truss
RE: Horizontal Reaction from Truss
11. All additional member connections shall be provided by others for forces as indicated.
That would include the horizontal force at Joints H and T and the reactions at Joints B and N.
BA
RE: Horizontal Reaction from Truss
Either way the truss seems spindly as they have it shown...
RE: Horizontal Reaction from Truss
The doubled top plates cannot span horizontally as beams over a 38' span. External buttresses are theoretically possible but probably not acceptable by the owner and likely not economical.
The Engineer of Record has to come up with a clever solution to the connection problem and perhaps modify the truss geometry in order to reduce horizontal deflection at the supports.
BA