The importance of strong-motion data in
engineering seismology and earthquake
engineering
Roberto PAOLUCCI
Department of Structural Engineering
Politecnico di Milano, ITALY
Outline
Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
Selection of real accelerograms based on
displacement-spectrum compatibility
Roberto Paolucci
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Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
3
 A benchmark problem
Seismic response analysis of a diaphragm wall (Foti and Paolucci, 2012)
D
B
variable
variabile
A’
E
B’
C
60
30
5
10
10
60
C’
z
bedrock
Points of control for acceleration
150 m
Roberto Paolucci
55 m
A
5 5 5 5
variable
variabile
10
Vs(z)
Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
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Selection of input records for non-linear time-history analyses
Earthquake
Recording Station
Epicentral Distance
Component
Recording device
Uncorrected amax
Val Comino 7/5/1984 M5.9
Irpinia 23.11.1980 M6.9
Atina
Bagnoli Irpino
10.3 km
22.6 km
NS
NS
KINEMETRICS SMA-1 (analog) KINEMETRICS SMA-1 (analog)
2
2
101 cm/s
129 cm/s
Corrected acceleration time histories from:
1)
2)
3)
European Strong Motion Database
ITalian ACelerometric Archive
PEER strong motion database
Roberto Paolucci
Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
ATINA NS record
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Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
ATINA NS record
ITACA “pad-strip”
procedure to safely
remove zero-padding
and ensure compatibility
of SM records
tapering + detrend on displacements
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Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
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Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
Atina
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Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
Bagnoli
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Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
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Displacement time histories at top of the wall – Atina record
2.5
ITACA
displacements [cm]
2.0
PEER
ESMDB
1.5
1.0
0.5
0.0
-0.5
-1.0
0
2
4
6
time [s]
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10
Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
11
peak values of displacement and bending moment – Atina record
peak displacement [m]
0.000
0
0.005
0.010
0.015
peak displacement [m]
0.020
0.025
-0.025
(a)
-0.020
-0.015
-0.010
-0.005
0.000
(b)
-2
-6
-8
itaca
-10
peer
-12
esmdb
end
confof
statica
excavation
-14
peak bending moment [kNm/m]
-400
0
-300
-200
-100
peak bending moment [kNm/m]
0
0
100
200
300
400
(b)
(a)
-2
-4
depth [m]
depth [m]
-4
-6
-8
-10
itaca
peer
esmdb
end
excavation
confof
statica
-12
-14
Roberto Paolucci
Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
Bending Moment
[kNm/m]
Atina
12
Displacement
[cm]
Left wall
Right wall
Left wall
Right wall
ITACA
-372.0
354.9
2.50
-2.05
PEER
-370.1
349.7
1.99
-2.06
ESMDB
-375.7
354.0
2.56
-1.90
Bending Moment
[kNm/m]
Bagnoli
Displacement
[cm]
Right
wall
Left wall
Left wall
Right wall
ITACA
-441.1
500.3
14.0
-12.6
PEER
-462.0
472.6
10.8
-11.7
ESMDB
-449.0
505.3
-54.6
-59.0
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Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
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Summary
 Consequences of processing procedure
 Limited on bending moments
 Relevant (20-30%) on displacements (important for PBD)
 Differences observed on a relatively rigid system (conservative design with PS
approach of EC8). Likely higher effects on more flexible systems
 “Engineering” rules to avoid gross errors in the use of real accelerograms used as input
motion for non-linear dynamic soil-structure interaction analyses:
 do not manipulate the corrected record provided by the database;
 prefer records corrected by acausal filtering;
 prefer digital records;
 check, before the numerical simulation, that velocities and displacements resulting
by integration of the input acceleration are not affected by unphysical drifts.
Roberto Paolucci
Outline
Influence of strong motion processing on numerical
simulations of soil-structure interaction problems
Selection of real accelerograms based on
displacement-spectrum compatibility
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Selection of real accelerograms based on displacementspectrum compatibility
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Introductory works at Politecnico from 2000 to 2010, for
characterization of long period ground motion
 displacement spectra at long periods (→ Faccioli et al., 2004)
 Study on the reliability of long period spectral ordinates from digital
accelerograms (→ Paolucci et al., 2008)
 GMPE at long periods (→ Cauzzi and Faccioli, 2008)
 PSHA at long periods for Italian sites (→ Faccioli and Villani, 2009)
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Reliability of long-period response spectral ordinates from digital accelerograms
Morge
Sep 8, 2005 Pennine Alps
(MW4.4, Re=17 km)
Zihuatanejo
Jan 11, 1997 Michoacán
(MW7.1, Re=143 km)
After Paolucci et al., 2008
"the elastic spectra from the most basic processing, in which only the pre-event
mean is removed from the acceleration time series, do not diverge from the
baseline-corrected spectra until periods of 10–20 sec (...) Akkar and Boore (2009)
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Probabilistic seismic hazard studies in Italy
Seismic Hazard Map of Italy
(0 – 2 s)
DPC-INGV Project S1 – 2005-2007
http://esse1.mi.ingv.it
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Probabilistic seismic hazard studies in Italy
Long period PSHA in Italy: maps of D10
DPC-INGV Project S5 – 2005-2007
Faccioli and Villani, 2009
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Probabilistic seismic hazard studies in Italy
Long period PSHA in Italy: map of TD
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Probabilistic seismic hazard studies in Italy
How to match short and long period PSHA results and put them in a
format for engineering applications ?
→ towards a target displacement spectrum for Italian sites (TDSI)
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Selection of real accelerograms based on displacementspectrum compatibility
Joint research activity of Politecnico di Milano & Università Federico II Napoli
Target displacement spectra for Italian sites
SIMBAD: a database for engineering analyses of long
period ground motion
Software REXEL-DISP v 1.1
Examples of application
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A Target Displacement Spectrum for Italian Sites
Broadband displacement spectrum for design, matching the Italian
NTC08 regulations at short periods with the long period PSHA
T  TC

TC  T  TD

S D (T )  TD  T  TE

TE  T  TF

T  TF
see NTC 08

2
 TC  T
a g S F0  
2
 T  4
D10  S Cc
D10  F  D10  S Cc  F 
D10  F
TF  T
TF  TE
D10,TD from Project S5, while ag, , S, Cc, F0, TC, TE, TF come from NTC08
: factor introduced to match short and long
periods (=1 for constant velocity)
F: long period site factor (from S5 project)
Roberto Paolucci
 4 2 D C    T  
10 c  
  log
  log C  
2
 ag F0TD 

   TD  
F  800/ VS 30 0.375
1
A Target Displacement Spectrum for Italian Sites
Italian norms NTC08
Long period PSHA
Connecting branch T-α
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A Target Displacement Spectrum for Italian Sites
 = 0.85 -1.4
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A Target Displacement Spectrum for Italian Sites
Comparison of TDSI with NTC08 (Italian seismic regulations)
TDSI
NTC08
MSD  0.025 amax  F0  TC  TD
d max  d g  0.025 S  a g  TC  TD
 0.025 amax  TC  TD
Roberto Paolucci
MSD  D10  S  CC
d max  D10  F
F  800/ VS 30 0.375  1.0  1.9
A: VS30 = 800 m/s; B: VS30 = 580 m/s; C/E:
VS30 = 270 m/s; D: VS30 = 140 m/s
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A Target Displacement Spectrum for Italian Sites
Site factors
NTC08
TDSI
Roberto Paolucci
Selection of real accelerograms based on displacementspectrum compatibility
Target displacement spectra for Italian sites
SIMBAD: a database for engineering analyses of long
period ground motion
Software REXEL-DISP v 1.1
Examples of application
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EC8 Site classes
Worldwide regions
SIMBAD: Selected Input Motions for displacement-Based
Assessment and Design
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Selection of real accelerograms based on displacementspectrum compatibility
Target displacement spectra for Italian sites
SIMBAD: a database for engineering analyses of long
period ground motion
Software REXEL-DISP v 1.1
Examples of application
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Software REXEL-DISP v 1.1 (www.reluis.it)
available at http://www.reluis.it
Roberto Paolucci
Selection of real accelerograms based on displacementspectrum compatibility
Target displacement spectra for Italian sites
SIMBAD: a database for engineering analyses of long
period ground motion
Software REXEL-DISP v 1.1
Examples of application
Roberto Paolucci
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Examples of application
Dependence on the target spectrum (NTC08 vs TDSI)
Aquila, TR = 475 years
 avg  11%,  max  26%
Roberto Paolucci
 avg  6%,  max  27%
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Examples of application
Dependence on seismicity level
(Aquila vs Udine, TR = 475 yr, TDSI)
 avg  6%   max  27%
Roberto Paolucci
 avg  9%   max  28%
Examples of application
Broadband compatibility
(Aquila, TR = 475 years, TDSI)
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Practical hints for using REXEL-DISP
Type of application
Hints
Search for 7 one- or twocomponent displacementspectrum compatible
accelerograms
Search for displacementspectrum compatible
individual records
Search for 30 displacementspectrum compatible
accelerograms
- preference to unscaled records
- use of wide magnitude and distance intervals (e.g., default values: 5-7
and 0-30 km) and any site class (due to the limited number of records on
some soil types in the SIMBAD database)
- ensure spectral matching over a rather broad range of vibration periods
(e.g., default values: 0.5-8 s)
- when searching for scaled records the use of limited magnitude and
distance range is found to be more feasible.
- preference to unscaled records
- use of wide magnitude and distance intervals (e.g., default values: 5-7
and 0-30 km) and any site class
- limit spectral compatibility to relatively small period ranges (e.g., 1-3 s)
- preference to unscaled records when selecting 30 one-component
records but the use of scale factors is advisable when searching for 30
two-component records.
- use of wide magnitude intervals (e.g., default values: 5-7) and any site
class
- ensure spectral matching over a rather broad range of vibration periods
(e.g., default values: 0.5-8 s)
- when searching for scaled records the use of limited magnitude and
distance range is found to be more feasible.
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Concluding remarks
Why using spectral displacements as a target for ground motion selection?
 the target magnitude range is “naturally” satisfied;
 no need to scale accelerograms;
 a broadband spectral compatibility is easily achieved (→ NLTHA of
MDOF systems – non-linear dynamic SSI – soil stability problems)
... but ...
 the accelerograms should be selected from high-quality strong-motion
databases, covering the seismic hazard levels and site conditions of
interest;
 the target spectrum should be carefully defined based on seismic hazard
studies at long periods
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Thank you !
Roberto Paolucci