Model Sure-Board Shear Walls in RISA-3D

[kmc23]

What would be the best way to model a sure-board shear wall in RISA-3D to accurately reflect it's rigidity? I have a relatively small two story building with a flexible roof diaphragm with a rigid 2nd floor diaphragm. The lateral system consists of a masonry wall and sure-board shear walls in the longitudinal direction and moment frames in the transverse direction. I'd like to model the building to figure out the force distribution to the lateral elements through the 2nd floor diaphragm and find out if the rigid diaphragm has a torsional deflection problem. So I'll need accurate rigidities for the lateral system to input into RISA. Thanks for your responses!

 

[msquared48]

Thank you. Now you will get an answer. Josh can help.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[JoshPlumSE]

As I understand it (from a Google seach) a Sure-Board system is really just a cold formed stud wall with some type of sheathing. It looked like drywall in the on-line pictures I saw, but in concept it could just as easily have been plywood or OSB.

There isn't really a "direct" way to model this. But, it is so similar to what we do for wood framed shear walls that I would just create a custom "wood nailing schedule" for this type of wall. Appendix F of the help file talks a little bit about this. We've done this a number of times when folks want to get some capacity out of wood walls with gypsum sheathing.

The key information that you need for getting a good analysis is the following:
Ga value (i.e the Apparent Shear Stiffness used in the NDS shear wall deflection equations)
Nail Spacing
Shear Capacity

The vertical stiffness of the wall will still assume wood studs at whatever spacing you specify. However, if you create a custom wood material (with custom E value) then you should be able to account for the difference in axial stiffness of your steel stud from a typical wood stud. For the studs, all you want to do is set E so that the EA value of your 2x4 stud matches the EA value of your stee stud. Make sense?