IBC Effective Seismic Weight

[TimmyH76]

Do I understand the IBC right that as long as the area is not used for storage no portion of the Live Load needs to be included in the effective seismic weight, except permenant equipment? Don't most people include a portion of the live load to account for things such as furniture, occupants...ect.?

 

[slickdeals]

A mass will contribute in dynamics only when it is tied in with the structure. According to the code, a parking garage that is full with cars will not have a seismic mass component. I think furniture etc. can be classified under the same category. HTH

 

[msquared48]

Personally, I do consider snow load as live load, but that is my personal call. Semantics I guess... So do not forget that too. You need to include 20% of the snow load in the seismic calcs for any snow load over 30 psf.

Mike McCann
McCann Engineering

 

[JMC3178]

Do you include the seismic weight of snow on a deck? Do I take 20% ground snow load, drift load, flat roof load or sloped roof load?

Thanks

 

[msquared48]

If you are talking about a small 4 X 8 foot deck, I would ignore it.

If you are talking about a deck on a rooftop where people assemble, I would definitely include it.

Regarding the issue of drift or flat, I would use the worst case considering that the flat snow load condition would occur with no wind, and the drift with wind in your load combinations.

Mike McCann
MMC Engineering