Calculating W for earthquake loads

[ttoma]

Hi all,

In calculating W for the calculations of earthquake loads, do we have to account for the weight of the partition walls supported directly on the foundations? A colleague of mine thinks that half of that weight should be accounted for. also, how do you account for the weight of masonry partitions? do you calculate the area of these walls and multiply it by the weight per unit area or simply use some UDL value?
Thanks

 

[JedClampett]

W is defined in Section 12.7.2 of ASCE 7-05. It says to use either the actual partition weight or 10 psf.

 

[msquared48]

The walls at the bottom story sitting on a slab on grade or thickened strip footings do need to be included if they are attached to the floor or roof diaphragm above, but only half of the height of the wall needs to be considered as half of the lateral force goes directly to the foundation. The rest is lumped into the floor/roof diaphragm above and included in the "W" for the seismic calcs.

Even if the walls are sitting on a short crawlspace. I would use the same approach. Not so though with a full basement. Then, the lower half of the wall would be lumped into the lower floor diaphragm and have to be resisted by the concrete foundation walls.

Mike McCann
McCann Engineering

 

[connect2]

'The effective seismic weight W including the total dead load .. (Dead load includes ...walls.. built in partitions, etc., etc.) and other loads listed below ' ...

'Where an allowance for partition loads is included in the floor load design, the actual partition weight or a minimum of 10psf of floor area, which ever is greater', would be included in W.

greater is what we're empahsizing here, but also I'm refering to ASCE 7-02. It is not a relevant code here but I use it for reference. Has this document changed much from 02 to 05?

In my opinion a masonry partition would be a built in or permanent partition or wall and not likely moved over the life of the structure therefore fit into the dead load catagory and not the live load catagory such as movable partitions or unknown partition distribution/location as is typical of office occupancies.