RISA3D for Wood Framing/ Residential Design
RISA3D for Wood Framing/ Residential Design
(OP)
Has anyone used RISA3D to model the framing of a wood structure, ie, a house? I would love to use it to capture all the loads from the ridge beam down to the beam in the basement. I just wonder if that's a reasonable request of the program.
-chuck
-chuck





RE: RISA3D for Wood Framing/ Residential Design
RE: RISA3D for Wood Framing/ Residential Design
Disclaimer: While I am a California registered SE, I actually work for RISA.... Just want to make that clear so that I can't be accused of mis-representing myself.
The RISA program can certainly be used for that purpose. However, there are some general issues with doing wood in FEM. Specifically related to stud walls and shear wall. Modelilng those is often more work than you'd like. For wood structures, it's much easier to limit your use of FEM to trusses, continuous beams, and such while avoiding the wood framed walls.
That being said, we'll see what we can do for shear walls and stud walls. Over the next six months or year, we'll be releasing a couple of versions specifically targeting commercial wood structures. The largest part of that development is related to modeling the walls.
RE: RISA3D for Wood Framing/ Residential Design
Is this something that Risa-Floor does?
RE: RISA3D for Wood Framing/ Residential Design
However, we do have some things in the works for this October's release that should really help with this type of structure (sloped floors in RISAFloor and wood bearing and shear walls). This forum is really NOT the best place to discuss these features.... It just sounds too much like a sales pitch. And, for the most part, we want to avoid that on these forums.
Therefore, you would probably be better served contacting the RISA support group directly (support@risatech.com) or the sales group (info@risatech.com) for a more detailed discussion of what those new features will do for you.
RE: RISA3D for Wood Framing/ Residential Design
It should also be noted, that RISA3D does a much better job with additive deflection calculations thant RISAFloor. Actually, if a beam in the roof is deflecting more due to it being supported on a beam in a lower level deflecting, RISAFloor only shows the deflection at the roof, due to the loads applied. The addition of the deflection of the support beam is not included, and therefore needs to be done by the user. RISA3D however, does provide the added deflection.
RE: RISA3D for Wood Framing/ Residential Design
1) you MUST model for the shear stiffness "G", rather than "E". (You cannot model for both. The plate algorithm can't handle a poisson's ratio greater than 0.5 - choose "G" and backsolve for an "E" value based on a "normal" poisson's ratio of about 0.2) (Good "G" values can be found in section 8 of APA's Report T2003-24.)
2) you MUST model the boundary elements (end studs, top & bottom plates, and the full ht trimmer studs around openings.) Model studs for the actual "E" value, not the "G" of the plywood.
3) If you are taking any vertical load, add studs to the model to take the load.
4) be careful about how you model slab support, and uplift stiffness of plate anchors.
The above may be more than you want to do, but anything less is "garbage in - garbage out". (Hand modeling is often easier.) The reasons for the above can be found in Advanced Mechanics of Materials texts. I can expand further if you would like, but it should probably be as a separate thread.
Scott Beard, PE, SE
RE: RISA3D for Wood Framing/ Residential Design
atr2
structural eng.