Post-frame model

[JStructsteel]

When modelling a wood post-frame building, what method do you use for the truss at the columns? Do you use a generic beam of some sort for the truss?

 

[WestLevel]

Depends on how I am feeling and geometry of the structure.

You can model the truss as truss members. but you will have to figure out how to resolve the DOF issue in the model.

You can make two models. and just put the truss reactions on the frame model.

 

[JStructsteel]

Thanks. I guess I am trying to get the base reactions and moments, and seems the stiffness of the truss or whatever member I model is important.
I dont know the truss geometry. Its a new design and no truss supplier is involved yet. I am gonna use the permacolumn system.

 

[XR250]

Me thinks these buildings are flexible enough that the stiffness of your truss or whatever should not meaningfully affect the base reactions.
I would not sharpen your pencil too much.

 

[JStructsteel]

Thanks. I will just model a generic truss in there.

 

[JStructsteel]

So I put a truss in for the span, and my reactions are still large. Is it realistic that my roofing (metal roofing, 2'-0" perlin spacing) would actually take some load and reduce that? If I put a horizontal force to mimic my diaphragm, I get that I need about 15 plf shear capacity from the roofing. Seems reasonable.

Any other help to get my posts to work?

(70' span, 16' roof, (3)-2x8 posts.

 

[jayrod12]

The NFBA post-frame manual has tested roofing assemblies and their available diaphragm capacities. 15 plf should be no problem. Most of the numbers in that document are betweeen 70-100 plf for various configurations.