...
How
...
to
...
specify
...
response
...
spectrum
...
scale?
...
The
...
value
...
for
...
each
...
force
...
related
...
design
...
parameter
...
of
...
interest,
...
including
...
story
...
drifts,
...
support
...
forces,
...
and
...
individual
...
member
...
forces
...
for
...
each
...
mode
...
of
...
response
...
shall
...
be
...
computed
...
using
...
the
...
properties
...
of
...
each
...
mode
...
and
...
the
...
response
...
spectra
...
defined
...
in
...
either
...
ASCE
...
7-05
...
Section
...
11.4.5
...
or
...
21.2
...
divided
...
by
...
the
...
quantity
...
R/I.
...
The
...
value
...
for
...
displacement
...
and
...
drift
...
quantities
...
shall
...
be
...
multiplied
...
by
...
the
...
quantity
...
Cd/I
...
(ASCE
...
7-05
...
Section
...
12.9.2).
...
Therefore,
...
response
...
spectrum
...
scale
...
factor
...
shall
...
be
...
g*I/R
...
where
...
g
...
is
...
acceleration
...
due
...
to
...
gravity
...
(use
...
386.4
...
in/sec
...
2 for
...
models
...
in
...
kips-inch
...
units
...
and
...
9.81
...
m/sec
...
2 for
...
models
...
in
...
kN-m
...
units).
...
After
...
analysis
...
is
...
performed,
...
review
...
the
...
Response
...
Spectrum
...
Base
...
Reaction
...
Table
...
and
...
refer
...
to
...
the
...
Base
...
shear
...
due
...
to
...
all
...
modes.
...
If
...
reported
...
dynamic
...
base
...
shear
...
is
...
more
...
than
...
85%
...
of
...
the
...
static
...
Base
...
shear
...
then
...
no
...
further
...
action
...
is
...
required.
...
However,
...
when
...
dynamic
...
base
...
shear
...
is
...
less
...
than
...
85%
...
of
...
static
...
base
...
shear
...
then
...
readjust
...
the
...
scale
...
factor
...
to
...
match
...
the
...
response
...
spectrum
...
base
...
shear
...
equal
...
to
...
85%
...
of
...
static
...
base
...
shear
...
(i.e.,
...
new
...
scale
...
factor
...
=
...
(g*I/R)
...
*
...
0.85*Static
...
base
...
Shear
...
/Response
...
Spectrum
...
base
...
shear
...
).
...
Use
...
this
...
readjusted
...
scale
...
factor
...
in
...
Response
...
Spectrum
...
and
...
rerun
...
the
...
2nd
...
analysis.