5N
Standar nasional lndonesia
tV,;
[r'rDo
fulvv,
Nvtp^f
C crl<
Tata *ara perem*ffimaa'D keta*ea'I&ft
ser,xpe
umtuk strurktun baergrsmam
geduae.eg
=B
.3
=s
.ZS;9t.08i0.01
EeEqEx gt?
darc ffi#s* gedumg
ridandisasi i{as Eoraa
ffiG
5.0
CONCLUSIONS AND RECOMMENDATIONS
of seismic hazard (PSHA) and site response
Based on the results
analyses
using the site-specific subsurface information from all soil borings G.{s., data) and
Downhole Seismic testing results, we develop the recofirmended surface elastic
response spectra for 5Yo damping for 500 and 2500 year events.
In developing the surface spectral accelerations, we consider the results of site
response analyses (SHAKE)
in combined with seismological (empirical) approaches.
The empirical approach accounts for average site amplification of global recording
data from different seismic environments for both subduction and shallow crustal
(background),
but does not including site-specific conditions. Recognizing
that
SHAKE can over damp high frequencies (low period) motions when site response is
strongly non-linear, we then use appropriate weighting factors to establish the design
response spectral accelerations at ground surface.
Figure 26A &.268 shows the design spectral amplification factor at ground
surface that envelopes the average (equal weight)
results at
T<2
sec and envelopes all results at
of the empirical and analyical
T>2
sec.
An additional
site
amplification due to basin effects was applied by multiplying the computed spectral
acceleration with factors
of
1.3 and 1.5 at
T: 3 sec and T > 5 sec based on
simnlations by Somerville, et. al. (2004) and Day, Steven, et. al. (2008).
Figure 27A shows the computed 500
&
25A0
yr surface response spectra (5%
damping), along with the smooth design surface spectral acceleration for 500-yr and
2500 yr event that envelope the mean computed surface spectra from SHAKE (Fig.
194
&
198).
According to RSNI-1726-201X, the recommended Sos (Sa atT:0.2 sec.) and
Sor (Sa at
T:
1 sec.) obtained from
the
site-specific seismic analysis (SSRA) in
conjunction with limitation of SSRA as stipulated in the ASCE 7-05 Chapter 21,
Site-Specific Ground Motion Procedures For Seismic Design"
is
oo
0.55 (Sds) and 0.55
(Sdl), respectively. Figure 27B shows the SYo-damped smooth design surface spectral
acceleration (500 yr
&
213
x 2500 yevent) along with the SNI 1726-2002
response
spectral for "medium" and "sofl" soils, and the upcoming RSNI 1726-zalx code (=
IBC 2009) for So and
SB
soil types.
To develop the surface response spectrum for different damping levels, we
computed the damping scaling factor from the results of site response analyses (Fig.
28A) and adjusted with the observation records (Fig. 288) for long period (> 3 sec.).
The smooth design surface spectrum (500
7%
yr and 213 x 2500 yr
event) for damping
& 10olo was developed by multiplying the 5% damped smooth design surface
spectrum (Fig. 27B) by a damping scaling factor (Fig. 28A) with results as shown on
Figure 29A (500 yr) and 298 (2/3x2500
yr)
and Table
1.
0.9
-Medi um
rsoft
4.7
0.6
o.s
ffi4 Ir
q(
to
a
0.4
iorl, Zone 3 (SNI 1726-20A2)
il . i\
\
(RSNI 1726-201x)
\
\
(SM 1726-2002)
ISNI1726-201x)
Iu
Soil, Zone 3
-SE
rSmooth
-Smooth
-
Design Spectrum (SNI 1726-2002)
Design Spectrum (RSNI 1726-2012)
\
\
\-**
./
,iN
4;t an
ft
SNI. lTt 6-zo tL
,-
lrl\
\
-t
_ r*.
{'
_Ets_
h:
-,,+ i.-
-l*i.
t*
t0
Period (s)
Figure 27B: Design and Coded Surface Spectrum (57" Damping)
1.1
Spectrum (500 yr)
1.0
-Computed
-Computed
0.9
0.8
Spectrum (2500 yr)
Design Spectrum
-Smooth
(SM 1726-2002)
Design Spectrum (2500 yr)
-smooth
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
0.01
Period (s)
Figure 27A: Computed and Design Surface Spectrum (500 & 2500 yr event) atSo/o Damping
