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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -2-
Content
• Recorded accelerograms
• Ground motion parameters
• Synthetic : stationary simulation
• Synthetic : non-stationary simulation
• Comparisons recorded/synthetic earthquakes
• Investigation of ground motion parameters
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -3-
Seismic loading Ductility demand varies with seismic loading
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -4-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -5-
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)
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -6-
Seismic loading - Recordings
Source: S. Godey http://www.neries-eu.org/
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -7-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -8-
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)
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -9-
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
∞
∫
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -10-
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
∫
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -11-
Seismic loading Recorded or synthetic accelerograms ?
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -12-
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??
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -13-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -14-
Seismic loading - Stationary simulation Pseudo non-stationarity using an envelop
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -15-
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)
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Seismic loading - Non-stationary simulation Sabetta & Pugliese method
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Seismic loading - Non-stationary simulation Sabetta & Pugliese method
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Seismic loading - Non-stationary simulation Sabetta & Pugliese method Influence of magnitude (M)
- amplitude increases with M
- period of maximal amplitude increases with M
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -19-
Seismic loading - Non-stationary simulation Sabetta & Pugliese method Influence of epicentral distance (R)
- amplitude decreases with increasing R
- shape unchanged
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -20-
Seismic loading - Non-stationary simulation Sabetta & Pugliese method Influence of soil conditions (S)
- frequency/period shift between stiff and deep
- amplification for shallow
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -21-
Seismic loading - Non-stationary simulation Sabetta & Pugliese method, compatible with
design spectra on average (SIA 261 Z3b soil A)
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -22-
Seismic loading - Non-stationary simulation Sabetta & Pugliese method, compatible with
design spectra on average (SIA 261 Z3b soil E)
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -23-
Seismic loading - Non-stationary adaptation Preliminary selection of a set of recorded TH
for best matching with response spectrum
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -24-
Seismic loading - Non-stationary adaptation Abrahamson (1992): non-stationary spectral
matching technique (wavelets)
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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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -26-
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]
Sion microzone A2, after modification
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]
Sion microzone A3, after modification
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -27-
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]
Martigny microzone M2, after modification
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]
Martigny microzone M3, after modification
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -28-
Seismic loading - Comparison Systematic comparison recorded/synthetic
Schwab & Lestuzzi (2007)
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -29-
Seismic loading - Comparison 9 recordings of ESMD
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -30-
Seismic loading - Comparison Average response spectrum (green) and
design spectrum
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -31-
Seismic loading - Comparison 5 simulation
techniques SIMQKE SIMQKE without
iterations SIMQKE recorded SIMQKE recorded
without iterations Sabetta & Pugliese
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -32-
Seismic loading - Comparison Average spectra for 100 generated
accelerograms for each simulation technique
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -33-
Seismic loading - Comparison SDOF results (various hysteretic models)
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -34-
Seismic loading - Comparison MDOF results
confirm SDOF results
do not depend on the selected accelerograms in the simulations
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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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -36-
Seismic loading - Comparison 2
Seismic analysis of the upper part of a dam
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -37-
Seismic loading - Comparison 2
Methodology
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -38-
Comparison 2 : 12 earthquakes ESMD
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -39-
Comparison 2 : 12 earthquakes ESMD
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -40-
Comparison 2 : 12 earthquakes ESMD
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Comparison 2 : 12 earthquakes ESMD
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Comparison 2 : 12 earthquakes ESMD
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Comparison 2 : 12 earthquakes ESMD
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -44-
Comparison 2: results with 33 synthetic TH
Transversal direction : statistical assessment
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -45-
Comparison 2 : results with 12 ESMD TH
Transversal direction : statistical assessment
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -46-
Comparison 2: results with 33 synthetic TH
Longitudinal direction : statistical assessment
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -47-
Comparison 2 : results with 12 ESMD TH
Longitudinal direction : statistical assessment
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -48-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -49-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -50-
Investigation - Ground motion parameters Methodology
Non-linear SDOF with different hysteretic models
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -51-
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]
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -52-
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 =⋅=
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -53-
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]
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -54-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -55-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -56-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -57-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -58-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -59-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -60-
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
CIVIL 706 - Selection/Synthetic earthquakes EPFL-EDCE-ENAC-SGC 2016 -61-
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