building separation

[broncosfan]

I am trying to calculate a required building separation per ASCE 7. For the special concentric braced frames, the deflection amplification factor is 5.0. For the building movement, I am adding the deflection of the braced frames plus the deflection of the diaphragm. The amplification factor gets applied to the braced frames. Does it also get applied to the diaphragm?

 

[JAE]

Here would be my logic on it:

The story drift is based on the drift at the "center of mass" of the story under consideration.

This center of mass is somewhere within the midst of the diahragm and will move [δ][sub]xe[/sub] which is the elastic analysis based on the base shear V distributed to each story.

This elastic analysis deflection, with flexible diaphragms, should include the distortion of the diaphragm as well as the deflection of the braces. So you would have a total deflection ([δ][sub]xe[/sub]) = brace defl. + diaphragm defl.

You then multiply the [δ][sub]xe[/sub] by C[sub]d[/sub] to get the "true" deflection. So the C[sub]d[/sub] then does apply to both the brace deflection and the diaphragm deflection.

With rigid diaphragms the diaphragm deflection is assumed to be small.