RISAFloor Seismic Base Shear CMU Wall w/ Brick Veneer

[memphiseng]

This is a problem I've been dealing with as a long time RISA3D user, accustomed to calculating lateral forces separately and applying them to the model. RISAFloor will calculate seismic mass and base shear, allowing you to push this through to RISA3D for design. The trouble I'm having is with is with incorporating the weight of brick veneer in these calculations.

I have tried creating a custom material set for the wall, with an increased density to approximate the combined CMU and brick veneer weight, but for some reason the wall weight in the RISA3D detail report is not always consistent.

How are others dealing with this situation? Are you calculating the seismic forces for the brick separately and applying them as linear loads to the RISA3D model?

 

[JoshPlumSE]

When we developed RISAFloor (If I remember correctly), we talked about the seismic weight of cladding and veneers and how they should be included in the seismic weight at each floor. I believe the solution we had was that the user just enter in a line load with a seismic weight at the diaphragm location of each story.

This works quite well, I believe, for the overall seismic force on the building. Of course, it doesn't work for the design of the local seismic forces (anchorage) of the wall. But, I don't believe the program has ever tried to do that.

I tried to download the Demo version of the program so that I could point you to the exact steps you need to take.... But, apparently RISA do longer has Demo versions of their program that you can download?! When did that happen? I guess I'm not surprised. It saddens me a bit, but I'm not surprised at all.

Caveats:
I worked for RISA for something like 16 years and I was a Vice President in charge of the support and training group before they were acquired by the German company who's name I cannot pronounce or spell. I now work for one of their main competitors. So, keep my potential bias in mind when reading my responses on anything related to RISA.

 

[memphiseng]

Thanks for the quick reply, Josh.

If I'm understanding you correctly, you're saying the solution is apply the tributary seismic weight as a Dyn Mass line load to the floor along the respective walls? This vertical Dyn Mass load is then incorporated into the base shear calculation, same as the Dyn Mass component of the floor load?

That makes sense and is simple enough.

 

[JoshPlumSE]

Yes, thank you. "Dyn Mass" is the term I was searching for. Apply a line load with Dyn Mass to account for tributary mass that you want from the cladding / veneer at each floor level.

I would have found that term if I could have installed the Demo version.... Oh well. We got there eventually.