zareian ground motion selection
TRANSCRIPT
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Ground Motion Selection and Scalingfor the analysis of the tall buildingcase studies
Farzin Zareian &PengZhong
May 7th, 2010
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1.5Km, Puente Hills
7.3Km, Hollywood
8.8Km, Raymond
11.5Km, Santa Monica
24.5Km, Elsinore
40.0Km, Sierra Madre56Km, San Andreas
SanAndreas
Raymon
d
Hollywo
odSan
ta
Monica
Newport-Ingl
ewood-RoseC
anyo
n
Elsinore(Whittier)
Elsinore(Chino)
SierraMadre(SanFernando)
Sierra Madre
(Cucamonga)Verdugo
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Significance of several modes of vibration in response ofthe building.
Similar ground motions for all structures.
Five hazard levels needs to be looked at.
A large number of motions are required (we used 15) tohave a reasonable estimate of the dispersion in EDP.
Challenges
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Disagg. for 2% / 50, T = 1.0 sec.
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Disagg. for 2% / 50, T = 5.0 sec.
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Site Hazard Characterization
In low probability hazard levels:
For long periods, hazard is dominated by two events. M
= 6.6 & R = 5km ( = 1.5), and M = 8 & R = 60km ( =2.5).
For short periods, hazard is dominated by single event.
M = 6.6 & R = 5km ( = 1.5).
In high probability hazard levels:
Domination of a single or two events is not significant.Epsilon ranges from -2 to 2 with a mean value of zero.
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Record Selection and Scaling Process
Selection :
Used a subset of NGA database (no aftershocks & etc.)
Only two recordings from any single event was selected
No restriction on Magnitude
Rmin&Rmax at 0.0 and 100.0 Km
Min and Max shear wave velocity = 180.0 and 1200.0
m/s Low pass filter cutoff frequency of the selected motions
are less than 0.1
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Record Selection and Scaling Process
Error
Weight
0
0.05
0.1
0.15
0.2
0 2 4 6 8 10 Period
10% %60 30%
26% %42 32%
0.5 3.0 7.0
Uniform
Variable
Scaling :
Maximum acceptable scale factor = 5.0
The scale factor, by which the smallest weighted error
between the target spectrum and the geometric meanspectrum of a single recording is acquired, is computed.
Records are matched between Tmin&Tmax at 0.5 & 10.0 sec.
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Record Selection and Scaling Process
Reduction in Sampling Frequency:
Reduced the ground motion time step from its originalto 0.04 (25 samples per second = 25Hz)
Eliminated the effect of aliasing by filtering originalground motions beyond the Nyquist frequency (12.5 Hz)
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Record Selection and Scaling Process
PBD, Roof
displacement, N-S
direction
A typical case of small difference
A typical case of larger difference
Original ground
motion
Filtered and down-
sampled ground
Motion
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MAXIMUM IDR
N-S, dt=original N-S, dt=.04
median
%16th
and %84th
Individual
earthquake
OVE
MCE
DBE
SLE43
SLE25
GM set difference
N-S E-W
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Response Spectra SLE25 (25 year)
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Response Spectra SLE43 (43 year)
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Response Spectra DBE (475 year)
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Response Spectra MCE (2475 year)
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Response Spectra OVE (4975 year)
7 unsclaed pairs are from simulatedmotions (URS/SCEC)
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0
0.5
1
1.5
2
2.5
3
3.5
0 1 2 3 4 5 6 7 8 9 10
(Sa(T)/g
[5%
criticaldam
ping]
Period (T)
Matched Spectra for TBI (OVE, 3 & 0.1, 7 & 0.6)
Target Spectrum
Median Spectrum
Indv. Spectrum
Rec./Scaled
Indv. SpectrumSimulated
Response Spectra OVE (4975 year)
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0
0.5
1
1.5
0 1 2 3 4 5 6 7 8 9 10
(Sa(T)/g
[5%
criticaldam
ping]
Period (T)
Matched Spectra for TBI (OVE, 3 & 0.1, 7 & 0.6)
Target Spectrum
Median Spectrum
Indv. Spectrum
Rec./Scaled
Indv. SpectrumSimulated
Response Spectra OVE (4975 year)
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5 sets of 15 ground motion records representing hazardlevels from 25 year return period to 5000 year returnperiod are selected for the purpose of los estimation.
Ground motion are matched to the target spectrum for thelocation of the buildings. (meets code requirements, andsimilar to procedures used by engineering seismologists)
Same ground motions are used for all buildings.
For the very low probability hazard level (OVE) a
combination of recorded and simulated motions is used
Summary