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• To: seaint(--nospam--at)seaint.org
• From: Eddie Gonzalez <Eagonzal(--nospam--at)ENG.CI.LA.CA.US>
• Date: Fri, 31 Jul 1998 08:27:20 -0700

```We are seeking to distribute the seismic lateral load on a bldg based on a
static approach.  It is for a multi level, rigid diaphragm shearwall building.
Due to the elev. diff. of the roof, various lateral load distribution methods
have been proposed.

Could anyone give me an idea as to how to best distribute the load on this
building or comment on the proposed methods?  Does the static method even
apply?

+ ZDir
|
|

12222222223444444444                5       +
1                  3                                  5       |
1                  3                                  5      30 FT
1                  3                                  5       |
1                  3                                  5       |
16666666663888888888888888885       + ------------------> XDir

<----30FT------>
<---------------------------90 FT------------------->

--------  PLAN VIEW ------

1AAAAAAAA3                                                        +
1                   3                                                         |
1                   3                                                         |
1                   3                                                        30
FT
1                   3BBBBBBBBBBBBBB5     +                |
1                   3                                 5      |                |
1                   3                                 5     15 FT        |
1                   3                                 5      +              +

--------   ELEVATION VIEW -----------

Approach 1:  Assume the building is one level in Z-Dir. Loading, Distribute the
Load according to rigidity at the point where they occur.  For Wall 3, apply
shear at top for roof A and at 15' for shear from roof B.  In XDir, apply load
at top of roof A and distribute load to each of the L-shape walls (6,8 and 2,4)
according to rigidity.

Issue: The shear in Xdir, from roof B would not be distributed properly.

Approach 2: Assume building has two levels.  In Z-Dir, Top level, assume DL
from 1/2 of Walls 1,2,6, and 1/2 of wall btw roof A and B for lateral story
load dist.  For lower level, assume remaining DL of wall 3, btw roof A & B +
1/2 wall below roof B and 1/2 of DL for walls 4,5,8 for lateral story load
dist.  Once V is computed, distribute story lateral loads per story, per
rigidity at each story