Standard Shear Walls - The Analysis of Irregular Shaped Structures - page 340

attention should be given to footnote 1 in the table, which states that walls that are
designed for seismic forces shall have an aspect ratio that does not exceed 2 : 1, unless
the nominal unit shear capacity is multiplied by 2 b / h . Failing to check this requirement
can lead to a lateral system that is underdesigned. Example 9.3 demonstrates this type
of error.

Example 9.3: Aspect Ratios, Wind vs. Seismic (See Fig. 9.10)
Assume that the shear walls along grid line 1 have been designed for a uniform wind
load applied to the diaphragm equal to 200 plf. A back check on the shear wall design
will be conducted using a seismic load equal to 190 plf, which is slightly less than the
calculated wind load. A third case will be checked with a calculated seismic load of
130 plf which is significantly less than the wind load. The wall sheathing is 15/32″ CDX
plywood (blocked) with 8d nails. The framing is Douglas Fir-Larch.
Table 4.3A from the SDPWS-08 provides nominal shear capacities for wind and
seismic loading. The values for wind loading have already been increased by 40 percent
in accordance with IBC Section 2306.3. Additional increases are not allowed.

Ω=20 . forASD design SDPWS- 08 Section 433 . .

v nominal = 730 plfwind , 15/32 with 8d @6 o. c.

′′ ′′

v nominal = 520 plfseismic , 15/32 ′′ with 8d @6 ′′ o.c.

F i g u r e 9.10 Aspect ratio, wind vs. seismic.