1 workshop on gmsm for nonlinear analysis, berkeley ca, october 26, 2006 atc-63 selection and...

1Workshop on GMSM for Nonlinear Analysis, Berkeley CA, October 26, 2006

ATC-63 Selection and Scaling MethodATC-63 Selection and Scaling Method

Charles KircherCharles Kircher

Curt B. HaseltonCurt B. Haselton

Gregory G. DeierleinGregory G. Deierlein


Ground Motion Objectives and Ground Motion Objectives and ConsiderationsConsiderations

Objectives of ATC-63 Project:

Develop a far-field set that is independent of site and building period

Use set to assess collapse of 70 buildings with various period

Use set as part of an assessment process to validate new building systems for

inclusion in building code

Minimize required scaling factors at collapse levels (PGA, PGV limits)

Maintain enough records to do meaningful statistics with collapse

predictions

Consideration of spectral shape:

For rare ground motions, spectral shape (ε) is extremely important

(Baker and Cornell).

Our selection does not account for this proper spectral shape.

We account for this by adjusting the collapse capacity distribution (mean

and sigma) after running the collapse simulations (forthcoming paper on

this method).


Selection of Far-Field Ground Motion SetSelection of Far-Field Ground Motion Set

Selection Criteria:

M > 6.5

R > 10km

PGA > 0.2g AND PGV > 15 cm/sec

Vs > 180 m/s (NEHRP A-D)

≤ 2 records per event

Lowest useable frequency < 0.25 Hz (4 seconds)

Strike-slip and thrust faults (consistent with

California)


Summary of Far-Field Ground Motion SetSummary of Far-Field Ground Motion Set

Intensity Measure Median

PGA [g] 0.43

PGV [cm/s] 38.0

Sa(T=1sec) [g] 0.36

- 22 records

- 14 events

- Mechanisms: - 9 strike-slip

- 5 thrust

Year Earthquake Faulting Mechanism Mag.Number

of Records

1999 Duzce, Turkey Strike-slip 7.1 1

1999 Hector Mine Strike-slip 7.1 1

1999 Kocaeli, Turkey Strike-slip 7.5 2

1999 Chi-Chi, Taiwan Thrust 7.6 2

1995 Kobe, Japan Strike-slip 6.9 2

1994 Northridge Blind thrust 6.7 2

1992 Landers Strike-slip 7.3 2

1992 Cape Mendocino Thrust 7.0 1

1990 Manjil, Iran Strike-slip 7.4 1

1989 Loma Prieta Strike-slip 6.9 2

1987 Superstition Hills Strike-slip 6.5 2

1979 Imperial Valley Strike-slip 6.5 2

1976 Friuli, Italy Thrust (part blind) 6.5 1

1971 San Fernando Thrust 6.6 1

Total: 22

ATC-63 Far-Field Ground Motion Set (Set C)


Ground Motion Scaling MethodGround Motion Scaling Method

Scaling method developed by C. Kircher

(details included in last slide)

Scaling steps:

Compute the average [Sa(T1)/PGV] for the full set

of ground motions

Compute record scale factors:

SF = [ average [Sa(T1)/PGV] of set ] * RecordPGV

Further scale the records by anchoring the mean

Sa(T1) to the target value


Scaled Far-Field Ground Motion SetScaled Far-Field Ground Motion Set

Records scaled to Sa(1s) = 0.9g

0 0.5 1 1.5 2 2.5 3 3.5 40

0.5

1

1.5

2

2.5

3

Period (seconds)

Sa

[g]


0 0.5 1 1.5 2 2.5 3 3.5 40

0.1

0.2

0.3

0.4

0.5

0.6

Period (seconds)

LN

(Sa

)

Dispersion in Scaled Ground Motion SetDispersion in Scaled Ground Motion Set

Dispersion in scaled record set

0.4-0.6


ClosingClosing

Thank you for your attention.

Questions?


Ground Motion Scaling MethodGround Motion Scaling MethodA Method for Scaling Horizontal Earthquake Time Histories

Kircher & Associates Consulting EngineersMarch 28, 1996

Definitions (Input Data):N Number of pairs of horizontal time history components that make up the set of earthquake records for each of site soil conditions (e.g., rock/rear-

source, soil near-source, rock/far-source and soil/far-source.PGVji Peak ground velocity, PGV, of time history, THji, (note: PGV values are provided by USGS/CDMG with processed time history and response

spectra data),Rsji Response spectrum (5%-damping) of time history, THji,Thji Time history of the ith pair in the jth horizontal direction (i.e., j = 1 or 2),TRS Target response spectrum (defined as 1.4 times the DBE, Z = 0.4, N=1.0)Teff Effective period of structure in seconds at intersection of capacity/demand curves.

Definitions (Calculated Data):ARS Response spectrum shape of time histories taken as the mean of composite response spectra, CRSi, normalized by composite peak ground

velocity, CPGVi,CPGVi Composite peak ground velocity of the ith horizontal time history pair,CRSi Composite response spectrum of the ith horizontal time history pair,MARS Response spectrum multiplier used to fit the response spectrum shape, ARS, to the target response spectrum, TRS,STHji Scaled time history of the ith pair in the jth horizontal direction.

Calculation Steps:

1.For near-source records, rotate each pair of horizontal components to fault normal and fault parallel directions (note: rotation affects all parameters, including time histories, THij, response spectra, RSij, and peak ground velocity, PGVij).

2.For each pair of earthquake components, calculate the composite spectrum, CRSi, and the composite peak ground velocity, CPGVi: CRSi = (RS1i2 + RS2i2)1/2 CPGVi = (PGV1i2 + PGV2i2)1/23.Find the average value of composite spectra normalized by composite peak ground velocity:

4.Determine the response spectrum multiplier, MARS, that is required to increase (or decrease) the response spectrum shape, ARS, such that it matches the target response spectrum, TRS, at the period(s) of interest (e.g., 1.4 times 0.60g for soil sites and 1.4 times 0.40g for rock sites at 1 second):

MARS TRS/ARS (ARS 1/T at Teff 1 second)

5.For each pair of earthquake time histories, scale both horizontal components by the ratio of the response spectrum multiplier to the composite peak ground velocity:

STH1i = (MARS/CPGVi)TH1i STH2i = (MARS/CPGVi)TH2i

1 workshop on gmsm for nonlinear analysis, berkeley ca, october 26, 2006 atc-63 selection and...

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