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Effects of Strong Motion Processing Procedureson Time Histories, Elastic and Inelastic Spectra

By Paolo Bazzurro, Brian Sjoberg, Nicolas Luco (AIR)

Walter Silva, Robert Darragh (Pacific Engineering and Analysis)

Presented at

COSMOS INVITED WORKSHOP

ON STRONG-MOTION RECORD PROCESSING

Richmond, CA, May 26-27, 2004

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Motivation

To quantify on a statistical basis the effects on ground motion time histories and elastic and inelastic spectra of

i. Causality of the filter

ii. Filter order

iii. Selection of the high-pass cut-off frequency

iv. Preservation or removal of residual displacement offset

We considered Butterworth filter only Near-source (distance R17km) ground motions from earthquakes with

moment magnitude ranging from 6.5 to 7.6 Two components rotated fault-parallel and fault-normal

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Earthquakes and Recording Stations

Rupture Distance VS30 HP LP Xcos() or DMFEarthquake Year Mag Mechanism (km) Station Name (m/s) (Hz) (Hz) Ycos()Imperial Valley 1979 6.5 S 8.5 Brawley Airport 209 0.10 40 0.7 1.05-1.54

1 El Centro Array #6 203 0.10 40 0.5 1.00-1.08

0.6 El Centro Array #7 211 0.10 40 0.5 1.00-1.08

14.2 Parachute Test Site 349 0.10 40 0.7 1.05-1.54

Loma Prieta 1989 6.9 R (oblique) 6.1 LGPC 466 0.10 0.8 1.04-1.17

Landers 1992 7.3 S 1.1 Lucerne 685 0.08 60 0.63 1.03-1.36

Kobe 1995 6.9 S 10.2 Amagasaki 256 0.10 40 0.57 1.02-.123

0.2 Kobe University 1043 0.10 30 0.42 0.94-0.99

2.5 Port Island (0 m) 198 0.10 0.3 0.76-0.97

1.2 Takarazuka 312 0.13 33 0.64 1.03-1.39

Northridge 1994 6.7 R 6.2 Jensen Filter Plant 373 0.20 0.79 1.04-1.16

7.1 Rinaldi Receiving Stn. 282 0.10 0.77 1.03-1.15

Kocaeli, Turkey 1999 7.4 S 17 Arcelik 523 0.07 50 0.26 0.71-0.96

12.7 Duzce 276 0.08 15 0.51 1.10-1.10

17 Gebze 792 0.08 25 0.23 0.68-0.96

4.8 Izmit 811 0.10 30 0.02 0.46-0.92

2.6 Yarimca 297 0.07 50 0.11 0.55-0.94

Chi-Chi, Taiwan 1999 7.6 R 4.4 TCU049 N/A 0.02 30 0.62 1.00-1.03

0.2 TCU052 N/A 0.04 50 0.61 1.00-1.02

1.1 TCU068 N/A 0.03 50 0.62 1.00-1.03

Additional Records List

Kocaeli, Turkey 1999 7.4 S 3.1 Sakarya 471 0.04 40 0.19 0.63-0.95

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Processing Techniques

Legend:AvailableNot Available

* Parallel component only

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Imperial Valley Brawley Airport H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR H-BRA053.ATR

El Centro Array #6 H-E06053.ATR H-E06053.ATR H-E06053.ATR H-E06053.ATR H-E06053.ATR H-E06053.ATR H-E06053.ATR H-E06053.ATR H-E06053.ATR

El Centro Array #7 H-E07053.ATR H-E07053.ATR H-E07053.ATR H-E07053.ATR H-E07053.ATR H-E07053.ATR H-E07053.ATR H-E07053.ATR H-E07053.ATR

Parachute Test Site H-PTS053.ATR H-PTS053.ATR H-PTS053.ATR H-PTS053.ATR H-PTS053.ATR H-PTS053.ATR H-PTS053.ATR H-PTS053.ATR H-PTS053.ATR

Loma Prieta LGPC LGP038.ATR LGP038.ATR LGP038.ATR LGP038.ATR LGP038.ATR LGP038.ATR LGP038.ATR LGP038.ATR LGP038.ATR

Landers Lucerne LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR LCN175.ATR

Kobe Amagasaki AMA230.ATR AMA230.ATR AMA230.ATR AMA230.ATR AMA230.ATR AMA230.ATR AMA230.ATR AMA230.ATR AMA230.ATR

Kobe University KBU230.ATR KBU230.ATR KBU230.ATR KBU230.ATR KBU230.ATR KBU230.ATR KBU230.ATR KBU230.ATR KBU230.ATR

Port Island (0 m) PRI230.ATR PRI230.ATR PRI230.ATR PRI230.ATR PRI230.ATR PRI230.ATR PRI230.ATR PRI230.ATR PRI230.ATR

Takarazuka TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR TAZ230.ATR

Northridge Jensen Filter Plant J EN122.ATR J EN122.ATR J EN122.ATR J EN122.ATR J EN122.ATR J EN122.ATR J EN122.ATR J EN122.ATR J EN122.ATR

Rinaldi Receiving Stn. RRS122.ATR RRS122.ATR RRS122.ATR RRS122.ATR RRS122.ATR RRS122.ATR RRS122.ATR RRS122.ATR RRS122.ATR

Kocaeli, Turkey Arcelik ARC000.ATR ARC000.ATR ARC000.ATR ARC000.ATR ARC000.ATR ARC000.ATR ARC000.ATR ARC000.ATR ARC000.ATR

Duzce DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR DZC180.ATR

Gebze GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR GBZ000.ATR

Izmit IZT090.ATR IZT090.ATR IZT090.ATR IZT090.ATR IZT090.ATR IZT090.ATR IZT090.ATR IZT090.ATR IZT090.ATR IZT004.ATR

Yarimca YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT000.ATR YPT004.ATR

Sakarya* SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR SKR090.ATR

Chi-Chi, Taiwan TCU049 TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR TCU049-N.ATR

TCU052 TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR TCU052-N.ATR

TCU068 TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR TCU068-N.ATR

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Response to Butterworth Filters of Different Orders

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Inelastic Displacement Response Spectra – What’s R?

max (inelastic)

(R = 4)

max (elastic)

max

Earthquake Accelerogram

Displacement Response

Time History(Tn = 1.0 sec)

Displaced Structure

-0.8-0.6-0.4-0.2

00.20.40.6

0 2 4 6 8 10 12 14 16

-10-505

101520

0 2 4 6 8 10 12 14 16

Displacement

Base Shear

max (elastic)

max (inelastic)

dy = max (elastic) / R

dy

Yield Strength

Single-Degree-of-FreedomStructure

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of Causality of the Filter

R=1 (Elastic)

Bandwidth for cascade acausal filter

Bandwidth upper bound for causal filter

Bandwidth upper bound for acausal filter

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of Causality of the Filter

R=8 (Severely Inelastic)

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of Filter Order: 4-pole vs. 5-pole Causal

R=1 (Elastic) R=8 (Severely Inelastic)

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of Filter Order: 4-pole vs. 5-pole Acausal

R=1 (Elastic) R=8 (Severely Inelastic)

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of Filter Order: 2p-2p vs. 2p-3p Acausal

R=1 (Elastic) R=8 (Severely Inelastic)

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of HP cut-off frequency: fHP vs. 1.5fHP --- 4-pole Causal Filter

R=1 (Elastic) R=8 (Severely Inelastic)

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of HP cut-off frequency: fHP vs. 1.5fHP --- 4-pole Acausal Filter

R=1 (Elastic) R=8 (Severely Inelastic)

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of HP cut-off frequency: fHP vs. 1.5fHP --- 2p-2p Cascade Acausal Filter

R=1 (Elastic) R=8 (Severely Inelastic)

~5s 1.5s

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of HP cut-off frequency: fHP vs. 1.5fHP --- 2p-2p Cascade Acausal Filter

R=1 (Elastic) R=8 (Severely Inelastic)

0.5s 2.0s

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of HP cut-off frequency: fHP vs. 1.5fHP --- 2p-2p Cascade Acausal Filter

R=1 (Elastic) R=8 (Severely Inelastic)

1.0s 3.0s

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Effects of Residual Displacement

R=1 (Elastic) R=8 (Severely Inelastic)

Notes: 1) normal components 2) 6 records only 3) Results for causal filters are similar

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Summary of Effects of Processing Techniques on Elastic and Inelastic Spectra

In general, effects are larger for inelastic than for elastic spectra and for longer periods at any given response level (i.e., R=1 through 8)

Causality of the filter does not systematically affect the amplitude of the spectra. The statistical impact on spectra due to the filter order is negligible Increasing the value of the HP cut-off frequency, fHP, generates inelastic spectra

that are systematically lower at periods much lower than 1/ fHP regardless of the causality of the filter. This can be in part explained by the lengthening of the effective period of vibration of structures in the post-elastic regime.

Records with residual displacement offset preserved generate inelastic response spectra that are consistently higher than those caused by records with offset removed. (Phenomenon observed for 6 fault-normal records only).

NOTE: See paper for effects on spectra caused by applying a filter to simulated ground motion records

© 2004 AIR Worldwide Corporation COSMOS WORKSHOP

Summary of Effects of Processing Techniques on Ground Motion TH’s

In general, effects are significant for PGD and, to a lesser extent, for PGV. The impact on other parameters (e.g., PGA, Arias Intensity, and duration) is negligible.

Causally filtered records have PGV and PGD values that are, on average, smaller (by 5-10% and 5-15%, respectively) than those of acausally filtered ones.

Acausally filtered records generally display a more prominent ramp of increasing displacement prior to the onset of strong-motion than causally filtered records. Peak-to-peak displacement amplitude, however, is similar for each processing technique.

The filter order does not affect the ground motion parameters considered here. Increasing the value of the HP cut-off frequency, fHP, generates records with

lower PGV and PGD values (5% and 15-20%, respectively), as expected. The values of PGV and PGD are considerably larger (5-20% and 50-60%,

respectively) in records with residual static offset preserved, as expected.