Risa 3d model and deflections

[leahweis90]

Hi there,

I have been working on this model that I have attached. I do not believe my model to be totally true but I am not quite sure what I have done wrong. The diagram is supposed to be modeled as MPP floor. Walls are framed wood sheathed with 19/32” and 10 nail. The deflections seem to be off. My story drift between 5th floor and roof is 5.301 inches.

I am also getting a lot a warning Logs about “Wall Panel: Holddowns and straps do not align in the wallpanel stack.” Will this affect my drift?


Is there a way in Risa to see the breakdown of deflations based on shear wall, diaphragm, and torsion? I would like to know where the deflections are coming from.

 

[driftLimiter]

You first need to understand how Risa 3d and how the NDS differently handle deflection of shear walls. There is an iterative step needed where you calibrate the modeled wall deflection to match the code equation. Without this step your results are essentially meaningless for deflections.

 

[JoshPlumSE]

Drift limiter has an excellent point, but I tend to thing the deflection issue is something different. What kind of diaphragm are you using. Rigid, Flexible or Semi-Rigid.

Note: I don't have RISAFloor on my computer... not even the Demo version. So, I can't test your model to see what's happening. I can usually help people without having the latest version of RISA-3D. But, RISAFloor is a different story. Especially when you're talking about how the RISAFloor model coverts into a RISA-3D model. That's probably a good one for their tech support.

Caveat:
I used to manage the tech support group for RISA. I was there for something like 16 years. But, I haven't been there for almost 5 years now! And, a lot has changed....