zareian ground motion selection

8/2/2019 Zareian Ground Motion Selection

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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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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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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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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



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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



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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

zareian ground motion selection

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