Effective seismic weight of interior walls

[smvk3]

I have a two story building. The interior partition walls at the ground level and upper level are all metal stud walls with deflection tracks up to the joists/beams above each level.

When calculating the effective seismic weight at the upper level, I know the code mandates that you add 10 psf for partitions. But what about the interior partition walls below the upper level? Do you have to add additional weight from these since they are connected to the underside of the beams/joists with deflection tracks?

What about at the roof level? Do you include the weight of the interior partition walls below since they are connected to the roof joists/beams with deflection tracks?

The commentary book on ASCE 7 has an example where they do not add any partition weight to the effective seismic weight at the roof level.

Just wanted some input how other engineers calculate this.

 

[XR250]

Yes, because they may have used deflection clips which will transmit seismic loads perp. and parallel to the wall. Even deflections tracks will in reality. No sense trying to sharpen your pencil on something like this.

 

[KootK]

Agreed. One way or another, some account should be given to the seismic mass contributed by fixed partition walls, both above and below the diaphragm under consideration. This is, conceptually, not much different from including exterior wall systems in the seismic mass. Most engineeres will include this as an approximate uniform load effect at each diaphragm level in my experience.

In practice, I rarely see a seismic mass contribution from interior walls assigned to the roof level. Such a contribution is sensible in my opinion, however.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.