The importance of strong-motion data in engineering seismology and earthquake engineering

The importance of strong-motion data in engineering seismology and earthquake

engineering

Roberto PAOLUCCI

Department of Structural Engineering

Politecnico di Milano, ITALY

Roberto Paolucci

Outline 2

Selection of real accelerograms based on displacement-spectrum compatibility

Influence of strong motion processing on numerical simulations of soil-structure interaction problems

Roberto Paolucci


A benchmark problem

Seismic response analysis of a diaphragm wall (Foti and Paolucci, 2012)

60 30 60

55

55

10

10

10

5

55

m

150 m

variabilevariabile

z

Vs(z) variable variable

bedrock Points of control for acceleration

A

B

C

D E A’

B’

C’

3

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Earthquake Val Comino 7/5/1984 M5.9 Irpinia 23.11.1980 M6.9 Recording Station Atina Bagnoli Irpino Epicentral Distance 10.3 km 22.6 km Component NS NS Recording device KINEMETRICS SMA-1 (analog) KINEMETRICS SMA-1 (analog) Uncorrected amax 101 cm/s2 129 cm/s2

Corrected acceleration time histories from:

1) European Strong Motion Database 2) ITalian ACelerometric Archive 3) PEER strong motion database


Selection of input records for non-linear time-history analyses

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ATINA NS record

5

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ATINA NS record

ITACA “pad-strip” procedure to safely remove zero-padding and ensure compatibility of SM records

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tapering + detrend on displacements

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Atina


8

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Bagnoli


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Displacement time histories at top of the wall – Atina record

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

0 2 4 6 8 10

time [s]

dis

pla

cem

ents

[cm

]

ITACA

PEER

ESMDB


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-14

-12

-10

-8

-6

-4

-2

0

-400 -300 -200 -100 0

peak bending moment [kNm/m]

dept

h [m

]

0 100 200 300 400

peak bending moment [kNm/m]

itaca

peer

esmdb

conf statica

(a) (b)

end of excavation

-14

-12

-10

-8

-6

-4

-2

0

0.000 0.005 0.010 0.015 0.020 0.025

peak displacement [m]

dept

h [m

]

-0.025 -0.020 -0.015 -0.010 -0.005 0.000

peak displacement [m]

itaca

peer

esmdb

conf statica

(a) (b)

end of excavation


peak values of displacement and bending moment – Atina record

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Bagnoli Bending Moment

[kNm/m] Displacement

[cm]

Left wall Right 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

Bending Moment

[kNm/m] 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


Atina

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Roberto Paolucci

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.


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Outline 14



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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)


Roberto Paolucci

16Reliability of long-period response spectral ordinates from digital accelerograms

After Paolucci et al., 2008

Zihuatanejo Jan 11, 1997 Michoacán (MW7.1, Re=143 km)

Morge Sep 8, 2005 Pennine Alps (MW4.4, Re=17 km)

"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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1717

Seismic Hazard Map of Italy (0 – 2 s)

DPC-INGV Project S1 – 2005-2007

http://esse1.mi.ingv.it

Probabilistic seismic hazard studies in Italy

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DPC-INGV Project S5 – 2005-2007Faccioli and Villani, 2009

Long period PSHA in Italy: maps of D10

Probabilistic seismic hazard studies in Italy

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1919Probabilistic seismic hazard studies in Italy

Long period PSHA in Italy: map of TD

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2020Probabilistic 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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SIMBAD: a database for engineering analyses of long period ground motion

Target displacement spectra for Italian sites

Software REXEL-DISP v 1.1

Examples of application


Joint research activity of Politecnico di Milano & Università Federico II Napoli

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FDTTTT

TTFCSDFDTTT

CSDTTT

T

T

TFSaTTT

NTCseeTT

TS

F

EF

FcFE

cED

CgDC

C

D

10

1010

10

2

2

0 4

08

)(

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

1

20

102

log4

log

D

C

Dg

c

T

T

TFa

CD

375.030/800 SVF

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)

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Italian norms NTC08

Long period PSHA

Connecting branch T-α


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= 0.85 -1.4


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Comparison of TDSI with NTC08 (Italian seismic regulations)

DC

DCgg

TTa

TTaSdd

max

max

025.0

025.0

NTC08 TDSI

DC TTFaMSD 0max025.0 CCSDMSD 10FDd 10max

9.10.1/800 375.030 SVF

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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Site factors

NTC08 TDSI


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3232SIMBAD: Selected Input Motions for displacement-Based Assessment and Design

Wor

ldw

ide

regi

ons

EC8

Site

cla

sses

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3434Software REXEL-DISP v 1.1 (www.reluis.it)

available at http://www.reluis.it

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3636

Dependence on the target spectrum (NTC08 vs TDSI) Aquila, TR = 475 years

%26%,11 max avg %27%,6 max avg


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3737

Dependence on seismicity level(Aquila vs Udine, TR = 475 yr, TDSI)

%27%6 max avg %28%9 max avg


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3838

Broadband compatibility(Aquila, TR = 475 years, TDSI)


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Type of application Hints

Search for 7 one- or two-component displacement-spectrum 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.

Search for displacement-spectrum compatible individual records

- 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)

Search for 30 displacement-spectrum compatible accelerograms

- 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.

Practical hints for using REXEL-DISP

Roberto Paolucci

4040Concluding 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

Roberto Paolucci

Thank you !

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The importance of strong-motion data in engineering seismology and earthquake engineering

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