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Re: Seismic and snow

[Subject Prev][Subject Next][Thread Prev][Thread Next] Not necessarily. A vacant building would not generate the additional seismic mass that is included due to storage load. Under the UBC 25% of storage loads are included in the seismic mass. For a heavy storage load of 250 psf, this can be equivalent to doubling your floor weight. It seems perfectly reasonable to include the same mass in the resisting calculations.

Every project I have ever done where we had to include snow or storage loads we have run both load cases (with or without) for the envelope solution. But if the load is assumed to be there for purposes of generating inertial forces, then it should be consistently assumed to be there in the resisting mass.

I'm not sure about the market forces equation, you probably need a higher coefficient on the $ factor.


Paul Feather PE, SE
www.SE-Solutions.net
pfeather(--nospam--at)SE-Solutions.net
----- Original Message ----- From: "Jordan Truesdell, PE" <seaint1(--nospam--at)truesdellengineering.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, June 28, 2005 1:21 PM
Subject: Re: Seismic and snow


This would assume (re: storage) that the building is never vacant. While the owner would certainly strive for such a condition, market forces do not always cooperate. (What would the symbol for market forces be for load combinations? Maybe 0.6D+0.6*(0.2*S or 0.4$)+.7*E ?)

Jordan

Paul Feather wrote:

I agree. This is similar to the question with regard to including storage loads in seismic. If a portion of the storage load is included for the lateral, it should also be included for the overturning.


Paul Feather PE, SE
www.SE-Solutions.net
pfeather(--nospam--at)SE-Solutions.net
----- Original Message ----- From: "Haan, Scott M POA" <Scott.M.Haan(--nospam--at)poa02.usace.army.mil>
To: <seaint(--nospam--at)seaint.org>
Sent: Tuesday, June 28, 2005 10:10 AM
Subject: RE: Seismic and snow



I think you can use the snow included in seismic weight to resist overturning with the load combinations that exist. I have had people argue with me if you have to use snow in seismic weight then you should be able to use that portion being included in seismic weight to reduce overturning. It seems
rational.

.6D+.6*(.2*S)+.7*E

The E has a .2*Sds*(D+.2*S) vertical reducing the .6D.



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