How to calculate story drift?

[Davidedoo]

I have designed a (home) two story box 30'x 45' with 9' first floor ht. and second floor ht. of 8'. I have calculated and designed the home for siesmic loads using site built shear walls. The plan checker is asking for the shear walls meet the story drift limitation of section 1630.10 of the California Building Code. Any help?

 

[shin25]

Shear wall in simple is a free standing cantilever beam. You can calculate the delection using the classical deflection equations for cantilever beams.

 

[whyun]

Check the 1997 UBC Standard 23-2 Sections 23.222 and 23.223 for how to calculate deflections in diaphragms or shear walls. I am assuming you have a wood framed building.

 

[UcfSE]

If the walls are wood framed, use the NDS or other appropriately referenced wood code. The NDS will give you deflection of the walls, based on more than just flexure. Drift is the deflection of the wall at story (i) minus the deflection of the wall at story (i-1), divided by the height of the wall at story i.

([Δ]_i - [Δ]_i-1)/h_i

This is commonly expressed as a fraction of the span (h), such as 1/400*span, or as the drift angle,

arctan(([Δ]_i - [Δ]_i-1)/h_i)

As the name implies, shear deformation is significant for shear walls and needs to be considered.