tV,; [r'rDo Nvtp^ffulvv, C crl 2 sec. An additional
siteamplification due to basin effects was applied by multiplying
the computed spectralacceleration with factors of 1.3 and 1.5 at T:
3 sec and T > 5 sec based onsimnlations 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 and2500 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.) andSor (Sa at T: 1 sec.) obtained from the site-specific
seismic analysis (SSRA) inconjunction with limitation of SSRA as
stipulated in the ASCE 7-05 Chapter 21, ooSite-Specific Ground
Motion Procedures For Seismic Design" is 0.55 (Sds) and 0.55(Sdl),
respectively. Figure 27B shows the SYo-damped smooth design surface
spectralacceleration (500 yr & 213 x 2500 yevent) along with
the SNI 1726-2002 response
5.0
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, wecomputed 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 yr and 213 x 2500 yr event) for damping7%
& 10olo was developed by multiplying the 5% damped smooth
design surfacespectrum (Fig. 27B) by a damping scaling factor (Fig.
28A) with results as shown onFigure 29A (500 yr) and 298 (2/3x2500
yr) and Table 1.
0.9
4.7
0.6
I o.sua
q(Lt 0.4oa
t0Period (s)
Figure 27B: Design and Coded Surface Spectrum (57" Damping)
r -Medi
-
rsoft (um Soil, Zone 3 (SM 1726-2002)
I
iorl, Zone 3 (SNI 1726-20A2)ISNI1726-201x)
A\\ -SE
(RSNI 1726-201x)
-Smooth Design Spectrum (SNI 1726-2002)
-
rSmooth Design Spectrum (RSNI 1726-2012)ffi4 Ir \il . i\ \-**
\./ 4;t an )
\,iN ft SNI. lTt 6-zo tL ,-I
I
\ lrl\ H \ -t _ r*. _Ets_{' h: -,,+ i.-
-l*i. + t*
-Computed Spectrum (500 yr)
-Computed Spectrum (2500 yr)
-Smooth Design Spectrum (SM 1726-2002)
-smooth Design Spectrum (2500 yr)
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.00.01
Period (s)
Figure 27A: Computed and Design Surface Spectrum (500 & 2500
yr event) atSo/o Damping
