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Seismic mass distribution

Seismic mass distribution

Seismic mass distribution

(OP)
Hi

I have a really stupid question. I have a one story building with concrete exterior walls (building height = 12' walls are 6''). For seismic mass calculation I am using the mass on the roof + half the exterior wall height (6'' x 150psf x perimeter x 6'). I dont see why this is not right. I ran into someone and he suggested not to use the exterior wall as it is self supporting.

The wall is attached at the roof. I dont get it how you can neglect the half of the wall tributary.

Thanks

RE: Seismic mass distribution

Mostly with you on this. Imagine a rectangular building. If you wanted the load to the base of a shear wall, it would be: roof trib + 1/2 perpendicular wall + parapet + entire weight of parallel shear wall resisting.

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.

RE: Seismic mass distribution

You don't need to take the seismic weight of the shear walls parallel to the EQ direction up into your diaphragm level loads.

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.

RE: Seismic mass distribution

(OP)

Quote (Kootk)

1/2 perpendicular wall

When you say 1/2 perpendicular wall you mean half the height right. Just clarifying.

Quote (Koootk)

You don't need to take the seismic weight of the shear walls parallel to the EQ direction up into your diaphragm level loads.
Agreed

RE: Seismic mass distribution

Quote (BAGW)

When you say 1/2 perpendicular wall you mean half the height right. Just clarifying.

Exactly. Obviously, there are some situations where a wall's seismic weight need not be assumed to be resisted by the diaphragms. To make a blanket statement that no wall's seismic weight makes it's way into the diaphragms is false in my opinion and telegraphs a fundamental lack of understanding. Perhaps your colleague really intended to include only shear walls aligned with the applied load in her statement. As you and I would probably know better than most, there are an almost infinite number of ways to express a technical opinion and have it be misinterpreted.

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.

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