Diaphragm Shear Forces

[Valdamos]

I have set up a RISA 3d model using plates in lieu of the diaphragm feature with the intent of coming up with the shear forces. I'm using precast members and am trying to come up with the necessary forces that the connections tying them together need to be designed for. I'm still fairly new to RISA, having mostly used it for shear walls with openings, and all of the precast jobs I have done thus far were simple enough that coming up with shear/chord forces by hand was relatively easy. The asymmetrical layout and openings in the diaphragm made things fairly difficult for this one, which is why I decided to try doing it with RISA. There are Plate Stresses, Plate Forces and Plate Corner Forces. I'm trying to figure out whats the simplest way from these to get the forces I'm resisting. At this point I'm reasonably certain the model is correct, I'm just still having trouble deciphering my shear forces. I have several ideas that I'm puzzling my way through, but am hoping someone with more experience can give me some guidance.

Any suggestions would be greatly appreciated.

Thanks!

 

[JoshPlumSE]

Diaphragm shear forces (Fxy) are reasonable for diaphram shear. However, for coments that you use for chord force design and such, I would tend to suggest using the "Internal Force Summation Tool". This takes the internal corner forces for each plate that is currently selected and converts them into a total force and moment along a cutting plane and local axis that you define.

Our RISANews blog should give a better (and more visual) description of exactly how this works... Though the application is a little different than the one you describe, you should get the general idea.