• To: seaint(--nospam--at)seaint.org
• From: "Sprague, Harold O." <SpragueHO(--nospam--at)bv.com>
• Date: Thu, 6 Apr 2000 15:37:15 -0500
```Gina,

The seismic lateral drift is amplified to account for nonlinear response.
Equation 33-2 is for seismic only.  The delta sub M value is the drift due
to the maximum inelastic response due to earthquake ground motion.  The
combined movement is obviously the square root of the sum of the squares.

You will have to calculate the combined amplified seismic lateral drift per
33-2.  Then you will have to calculate the elastic lateral drift due to wind
to see which drift case governs.

There is nothing on building separation due to wind, but you could make a
case for full lateral wind drift on one building with the adjacent building
being shielded (no drift).  The only ways for buildings to deflect in
opposing directions due to wind would be the VERY rare cases of:
1.	Tall skinny dynamically sensitive structures which could be excited
by vortex shedding
2.	Wind directional effects due to building shape (similar to
quartering winds on a sail)
The VERY rare cases constitute only 0.00065% of all the structures ever
built since the year 1253 (humor intended).

There is commentary in the ASCE 7 to determine if a structure is dynamically
sensitive.

Regards,
Harold Sprague

> -----Original Message-----
> From:	Gobo, Gina [SMTP:ggobo(--nospam--at)DLRGROUP.com]
> Sent:	Thursday, April 06, 2000 3:04 PM
> To:	'seaint'
>
> Does Equation 33-2 of the 1997 UBC apply to wind loads as well?
>
> I have a structure whose design base shear is governed by wind. It is
> being
> built adjacent to an existing structure whose base shear is governed by
> seismic. I would like to calculate the building deflections so that I may
> figure out what kind of clearance I need between the buildings.
>