Truss Deflections
Truss Deflections
(OP)
I'm sure you are all familiar with the standard output from the truss manufacturers that shows the loads, geometry etc... According to the code they are required to provided deflection (vertical) values for the DL and TL. I've got a copy of ANSI/TPI 1-2007 here and I can't seem to find any equations, algorithms or specification of method used to arrive at those deflection numbers. I've done quite a bit of reading on trusses recently and I've seen matrix method, energy method, castiglianlo's method thrown around. Being that the truss manufacturer's use software that is proprietary and they probably protect their methods quite carefully its not like I can email them and ask what is their standard method of calculating deflections. Just wondering if anyone has any experience or insight about real world truss deflections and could send me searching in the right direction.






RE: Truss Deflections
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Truss Deflections
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MAP
RE: Truss Deflections
That will get you close. Most of the deflection comes from axial shortening or elongation of the members so modeling as pinned versus fixed does not make much difference. There is nothing proprietary about the way they calc deflections - it is just simple matrix analysis - just like you can do with a 2-d frame program - unless they are taking into account plate creep - which would be proprietary.
RE: Truss Deflections
solving an indeterminate truss involves more work ... you can do it on a s/sheet or you can use FEA.
as michael says, typically hand calcs neglect continous chords, pinning the elements at each joint; which is probably conservative for the truss element loads, but possibly unconservative for the local stresses of the continuous chords.
Quando Omni Flunkus Moritati
RE: Truss Deflections
RE: Truss Deflections
getting the defelction of the truss will be somewhat of a pain ... element load > element stress > element strain > element elongation (ok that was the easy part) now put all the element elongations together ... what assemble a bunch of arcs ?? that's got to be only a short step away from insanity !
if you need deflections, i think you need FEA.
Quando Omni Flunkus Moritati
RE: Truss Deflections
I can send you the procedure for trusses in pdf if you like.
In Russia building design you!
RE: Truss Deflections
RE: Truss Deflections
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Truss Deflections
Thanks.
RE: Truss Deflections
RE: Truss Deflections
In Russia building design you!
RE: Truss Deflections
i assume that means multiply the n and N and L/EA values for each element of the truss and sum ?
Quando Omni Flunkus Moritati
RE: Truss Deflections
In Russia building design you!