Selection of time-histories Synthetic earthquakes€¦ · CIVIL 706 - Selection/Synthetic...

CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -1-

EDCE: Civil and Environmental Engineering CIVIL 706 - Advanced Earthquake Engineering

Selection of time-histories Synthetic earthquakes


Content

•  Recorded accelerograms

•  Ground motion parameters

•  Synthetic : stationary simulation

•  Synthetic : non-stationary simulation

•  Comparisons recorded/synthetic earthquakes

•  Investigation of ground motion parameters


Seismic loading Ductility demand varies with seismic loading


Seismic loading

• Recorded accelerograms

- real events

- number limited but exponentially increasing - limited variability due to the limited recorded EQs - not conservative as design spectra

•  Synthetic

- stationary simulation - non-stationary simulation - conservative following

the design codes


Seismic loading - Recordings •  Strong motion networks

- for engineering purposes (attenuation relationships, soil amplifications, site effects, structure monitoring…)

- in urbanized areas

- on various soils - accelerometers (more noise, no clipping, broadband)

•  Seismological networks

- for seismological purposes (source location, internal earth studies) - in quiet areas - on hard rock - velocimeters (more sensitive, clipping, short period or broadband)


Seismic loading - Recordings

Source: S. Godey http://www.neries-eu.org/


Seismic loading - Recordings Where to find accelerometric data ? •  Selected datasets (CD or website):

•  Earthquake Strong Motion Collection (US and more) http://www.ngdc.noaa.gov/hazard/fliers/se-0308.shtml

•  European Strong Motion database (Ambraseys et al., 2002) http://www.isesd.hi.is

•  ESM Database http://esm.mi.ingv.it

•  Complete databases including recent events (websites with search engines)

•  Worldwide: Center for engineering strong motion data including COSMOS (worldwide) http://www.strongmotioncenter.org/

•  Switzerland: http://seismo.ethz.ch •  France: RAP http://rap.resif.fr


Ground motion parameters •  To classify or select ground motions for experimental

tests or modelling. •  To quantify the seismic demand in the design codes Should represent the potential “danger” for structures Peak Ground Acceleration (PGA) most commonly used

but high frequency parameter Now standardization from the accelerometric networks

(e.g. NERIES project)


Ground motion parameters Direct parameters based on acceleration: •  Raw PGA (cm/s2) from unfiltered record •  PGA (cm/s2) from filtered record at 0.1 Hz •  Arias intensity AI (cm/s) •  Trifunac duration TD (s) •  Cumulative Absolute Velocity CAV (cm/s)

Based on velocity or displacement: •  PGV (cm/s) representative around 1 Hz •  PGD (cm) above 1m/s2 low frequency parameter

€

AI =π2g

[a(t)]2dt0

∞

∫

€

TD = t95% − t5%

€

tα ∍ αAI =π2g

[a(t)]2dt0

tα

∫

€

CAV = a(t) dt0

∞

∫


Ground motion parameters Spectral parameters computed for SDOF systems: •  PSV (5%) (from 0.1Hz-50Hz) (cm/s) •  Housner intensity or Response Spectrum Intensity

(cm) found to be well-correlated with ductility demand

Computed from PSV •  PSA (5%) •  PSD (5%)

€

IH = Sv (5%,T)dT0.1

2.5

∫


Seismic loading Recorded or synthetic accelerograms ?


Seismic loading - Stationary simulation

SIMQKE software Based on random vibrations theory (Gasparini & Vanmarcke, 1976) Time windows of an random stationary function

Poor quality simulation of real earthquakes OK for linear behaviour, non-linear??


Seismic loading - Stationary simulation •  Poor quality simulation of

real EQ •  Non-varying frequency

content (∑ sinus) •  Based on a statistical

relationship between Fourier and Response spectra

•  Random Phases •  Time-envelope to

simulate non-stationarity •  Iterations on Fourier

spectrum to converge to the target Response spectrum


Seismic loading - Stationary simulation Pseudo non-stationarity using an envelop


Seismic loading - Non-stationary simulation

Sabetta & Pugliese method Empirical model calibrated on Italian accelerograms

Definition using 3 parameters Magnitude M Epicentral distance R Soil conditions S (stiff, shallow or deep)


Seismic loading - Non-stationary simulation Sabetta & Pugliese method


Seismic loading - Non-stationary simulation Sabetta & Pugliese method Influence of magnitude (M)

- amplitude increases with M

- period of maximal amplitude increases with M


Seismic loading - Non-stationary simulation Sabetta & Pugliese method Influence of epicentral distance (R)

- amplitude decreases with increasing R

- shape unchanged


Seismic loading - Non-stationary simulation Sabetta & Pugliese method Influence of soil conditions (S)

- frequency/period shift between stiff and deep

- amplification for shallow


Seismic loading - Non-stationary simulation Sabetta & Pugliese method, compatible with

design spectra on average (SIA 261 Z3b soil A)


Seismic loading - Non-stationary simulation Sabetta & Pugliese method, compatible with

design spectra on average (SIA 261 Z3b soil E)


Seismic loading - Non-stationary adaptation Preliminary selection of a set of recorded TH

for best matching with response spectrum


Seismic loading - Non-stationary adaptation Abrahamson (1992): non-stationary spectral

matching technique (wavelets)


Abrahamson matching for 12 TH – EC8/SIA

10-2 10-1 100 1010

1

2

3

4

5Sa

[m/s

2]SIA 261 soil class A, before modification

10-2 10-1 100 1010

1

2

3

4

5

Sa [m

/s2]

SIA 261 soil class A, after modification

10-2 10-1 100 1010

1

2

3

4

5

Sa [m

/s2]

SIA 261 soil class B, before modification

10-2 10-1 100 1010

1

2

3

4

5

Sa [m

/s2]

SIA 261 soil class B, after modification

10-2 10-1 100 101

period [s]

0

1

2

3

4

5

Sa [m

/s2]

SIA 261 soil class C, before modification

10-2 10-1 100 101

period [s]

0

1

2

3

4

5

Sa [m

/s2]

SIA 261 soil class C, after modification


Abrahamson matching for 12 TH – Sion

10-2 10-1 100 1010

2

4

6

8Sa

[m/s

2]Sion microzone A1, before modification

10-2 10-1 100 1010

2

4

6

8

Sa [m

/s2]

Sion microzone A1, after modification

10-2 10-1 100 1010

2

4

6

8

Sa [m

/s2]

Sion microzone A2, before modification

10-2 10-1 100 1010

2

4

6

8

Sa [m

/s2]


10-2 10-1 100 101

period [s]

0

2

4

6

8

Sa [m

/s2]

Sion microzone A3, before modification

10-2 10-1 100 101

period [s]

0

2

4

6

8

Sa [m

/s2]



Abrahamson matching for 12 TH – Martigny

10-2 10-1 100 1010

2

4

6

8

10Sa

[m/s

2]Martigny microzone M1, before modification

10-2 10-1 100 1010

2

4

6

8

10

Sa [m

/s2]

Martigny microzone M1, after modification

10-2 10-1 100 1010

2

4

6

8

10

Sa [m

/s2]

Martigny microzone M2, before modification

10-2 10-1 100 1010

2

4

6

8

10

Sa [m

/s2]


10-2 10-1 100 101

period [s]

0

2

4

6

8

10

Sa [m

/s2]

Martigny microzone M3, before modification

10-2 10-1 100 101

period [s]

0

2

4

6

8

10

Sa [m

/s2]



Seismic loading - Comparison Systematic comparison recorded/synthetic

Schwab & Lestuzzi (2007)


Seismic loading - Comparison 9 recordings of ESMD


Seismic loading - Comparison Average response spectrum (green) and

design spectrum


Seismic loading - Comparison 5 simulation

techniques SIMQKE SIMQKE without

iterations SIMQKE recorded SIMQKE recorded

without iterations Sabetta & Pugliese


Seismic loading - Comparison Average spectra for 100 generated

accelerograms for each simulation technique


Seismic loading - Comparison SDOF results (various hysteretic models)


Seismic loading - Comparison MDOF results

confirm SDOF results

do not depend on the selected accelerograms in the simulations


Seismic loading - Comparison Conclusions:

non-stationnary simulation performs clearly better

- ductility demand - energy demand do not use convergence procedures

- lost of demand and variability - not conservative results properly define target spectrum

- realistic


Seismic loading - Comparison 2

Seismic analysis of the upper part of a dam


Seismic loading - Comparison 2

Methodology


Comparison 2 : 12 earthquakes ESMD


Comparison 2: results with 33 synthetic TH

Transversal direction : statistical assessment


Comparison 2 : results with 12 ESMD TH

Transversal direction : statistical assessment


Comparison 2: results with 33 synthetic TH

Longitudinal direction : statistical assessment


Comparison 2 : results with 12 ESMD TH

Longitudinal direction : statistical assessment


Seismic loading - Comparison 2 Conclusions:

no significant difference

- similar displacement demand - smaller variability for ESMD (selection process) investigations for 2 natural frequencies only

- extensive studies are needed for generalization - damping is also to investigate tentative explanation

- relative small energy dissipation


Investigation - Ground motion parameters 164 ground motions extracted from the ESM

database - M>5 - PGA>0.6 m/s2 - Ep. D. free

4.5

5

5.5

6

6.5

7

7.5

8

0 20 40 60 80 100 120 140 160 180 200

Epicentral Distance [Km]

Mag

nitu

de


Investigation - Ground motion parameters Methodology

Non-linear SDOF with different hysteretic models


Investigated parameters Spectral intensity according to Nau and Hall

( ) ( )∫ ⋅=0.2

285.0715.11 dTPaSI SV ζζ

%5=ζ

0.285 2.0T [s]

PSV [m/s]

0.285 2.0T [s]

PSV [m/s]


Investigated parameters Modified definition of spectral intensity

T0 Ts

T [s]

PSV [m/s]

T0 Ts

T [s]

PSV [m/s]

F

ddy dmax

Fy

Fmax

F

ddy dmax

Fy

Fmax

( ) ( )∫ ⋅Δ

=sT

T SV dTPT

RfbSI0

1,, 0 ζζ

00 f

RRTTs =⋅=


Investigated parameters Slope (m) of acceleration response spectrum

( ) ( ) ( )s

saa

fffSfSRfm

−

−=

0

00

,,,,

ζζζ

Rff s0=

€

ζ =10% − 20% − 30%

fS f0

f [Hz]

Sa [m/s2]

fS f0

f [Hz]

Sa [m/s2]


Investigated parameters Average slope (m) of Sa

( )( ) ( )

2

,,,,

0

0,00

s

meanaa

fffSfS

Rfm−

−=

ζζζ

%5=ζ

( )( )

s

f

f a

meana ff

dfsfS s

−

⋅=∫

00,

0

,ζ

ζfS f0

f [Hz]

Sa [m/s2]

Sa, mean

fS f0

f [Hz]

Sa [m/s2]

Sa, mean


Results - Correlation coefficients Magnitude, low correlation

f0 = 1.0 Hz; R = 3

1

2

3

4

5

6

7

8

9

10

11

5 5.5 6 6.5 7 7.5 8

Magnitude

Duc

tility

Dem

and


Results - Correlation coefficients Magnitude, low correlation

Magnitude - Ductility Demand correlations, R = 3

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Frequency [Hz]

Cor

rela

tions

Magnitude


Results - Correlation coefficients Spectral intensity (SIb), strong correlation

f0 = 1.0 Hz; R = 3

1

2

3

4

5

6

7

8

9

10

11

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45

SI b

Duc

tility

Dem

and


Results - Correlation coefficients Comparison between spectral intensities

Spectral Intensity - Ductility Demand correlations, R = 3

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Frequency [Hz]

Cor

rela

tions

SI aSI b


Results - Correlation coefficients Slopes of acceleration response spectrum

Slope - Ductility Demand correlations, R = 3

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Frequency [Hz]

Cor

rela

tions Slope 10

Slope 20Slope 30Average Slope


Results - Correlation coefficients Average slope ≈ spectral intensity (SIb)

SI b / Average slope - Ductility Demand correlations, R = 3

0.4

0.5

0.6

0.7

0.8

0.9

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

Frequency [Hz]

Cor

rela

tions

Average slopeSI b


Investigation - Ground motion parameters

Conclusions: classification of the earthquake agressivity

- spectral intensity - slope of acceleration response spectrum spectral acceleration near design spectrum

- at initial natural period (T0) - if possible till Ts (secant stiffness) rational choice of the engineer

- most dangerous or another one

Selection of time-histories Synthetic earthquakes€¦ · CIVIL 706 - Selection/Synthetic...

Documents

Transcript of Selection of time-histories Synthetic earthquakes€¦ · CIVIL 706 - Selection/Synthetic...