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

Influence of strong motion processing on numerical simulations of soil-structure interaction problems A benchmark problem Seismic response analysis of a diaphragm wall (Foti and Paolucci, 2012)

Selection of input records for non-linear time-history analyses Influence of strong motion processing on numerical simulations of soil-structure interaction problems Selection of input records for non-linear time-history analyses Corrected acceleration time histories from: 1) European Strong Motion Database 2) ITalian ACelerometric Archive 3) PEER strong motion database

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

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

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

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

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

Displacement time histories at top of the wall – Atina record Influence of strong motion processing on numerical simulations of soil-structure interaction problems Displacement time histories at top of the wall – Atina record

Influence of strong motion processing on numerical simulations of soil-structure interaction problems peak values of displacement and bending moment – Atina record

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

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

Outline Influence of strong motion processing on numerical simulations of soil-structure interaction problems Selection of real accelerograms based on displacement-spectrum compatibility

displacement spectra at long periods (→ Faccioli et al., 2004) Selection of real accelerograms based on displacement-spectrum compatibility 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)

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)

Seismic Hazard Map of Italy (0 – 2 s) Probabilistic seismic hazard studies in Italy 17 Seismic Hazard Map of Italy (0 – 2 s) DPC-INGV Project S1 – 2005-2007 http://esse1.mi.ingv.it 17

Long period PSHA in Italy: maps of D10 Probabilistic seismic hazard studies in Italy 18 Long period PSHA in Italy: maps of D10 DPC-INGV Project S5 – 2005-2007 Faccioli and Villani, 2009 18

Long period PSHA in Italy: map of TD Probabilistic seismic hazard studies in Italy 19 Long period PSHA in Italy: map of TD 19

→ towards a target displacement spectrum for Italian sites (TDSI) Probabilistic seismic hazard studies in Italy 20 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) 20

Target displacement spectra for Italian sites Selection of real accelerograms based on displacement-spectrum 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

F: long period site factor (from S5 project) 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 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)

A Target Displacement Spectrum for Italian Sites Italian norms NTC08 Long period PSHA Connecting branch T-α

A Target Displacement Spectrum for Italian Sites  = 0.85 -1.4

Comparison of TDSI with NTC08 (Italian seismic regulations) A Target Displacement Spectrum for Italian Sites Comparison of TDSI with NTC08 (Italian seismic regulations) NTC08 TDSI A: VS30 = 800 m/s; B: VS30 = 580 m/s; C/E: VS30 = 270 m/s; D: VS30 = 140 m/s

Comparison of TDSI with NTC08 (Italian seismic regulations) A Target Displacement Spectrum for Italian Sites Comparison of TDSI with NTC08 (Italian seismic regulations) Site class A TDSI NTC08 TDSI

A Target Displacement Spectrum for Italian Sites Site factors NTC08 TDSI

Comparison of TDSI with NTC08 (Italian seismic regulations) A Target Displacement Spectrum for Italian Sites Comparison of TDSI with NTC08 (Italian seismic regulations) Aquila - SLV Udine - SLV

A Target Displacement Spectrum for Italian Sites Comparison of long period response spectral ordinates from different seismic regulations (NTC08, EC8, ASCE 7-10, NZS1170) - site class B (NTC08, EC8) or C (NZS1170, ASCE 7-05)

Displacement spectrum Range of variability of TD A Target Displacement Spectrum for Italian Sites 30 Displacement spectrum Range of variability of TD EC8 1.2 s for M < 5.5 2.0 s for M > 5.5 NTC08 Ranging from about 1.8 s (for ag/g = 0.05) to 2.8 s (for ag/g = 0.30) NZS 1170.5 3.0 s ASCE 7-05 Ranging from about 4 s (for M = 6.0-6.5) to 16 s (for M = 8.0-8.5) TDSI 3.7 s median value,   = 1.4 s after SIMBAD database

Target displacement spectra for Italian sites Selection of real accelerograms based on displacement-spectrum 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

Worldwide regions EC8 Site classes SIMBAD: Selected Input Motions for displacement-Based Assessment and Design 32 Worldwide regions EC8 Site classes

Target displacement spectra for Italian sites Selection of real accelerograms based on displacement-spectrum 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

available at http://www.reluis.it Software REXEL-DISP v 1.1 (www.reluis.it) 34 available at http://www.reluis.it

Target displacement spectra for Italian sites Selection of real accelerograms based on displacement-spectrum 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

Dependence on the target spectrum (NTC08 vs TDSI) Examples of application 36 Dependence on the target spectrum (NTC08 vs TDSI) Aquila, TR = 475 years

Examples of application 37 Dependence on seismicity level (Aquila vs Udine, TR = 475 yr, TDSI)

Examples of application 38 Broadband compatibility (Aquila, TR = 475 years, TDSI)

Type of application Hints Practical hints for using REXEL-DISP 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 - 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

the target magnitude range is “naturally” satisfied; Concluding remarks 40 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

Thank you !