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ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines

DHS/FEMA ATC-58 ProjectDHS/FEMA ATC-58 Project

Selection and Scaling of GroundSelection and Scaling of Ground

MotionsMotions

Yin-Nan Huang

University at Buffalo

Andrew Whittaker, S.E.,

University at Buffalo

ATC-58 SPP Team Lead

Ron Hamburger, S.E.

Simpson, Gumpertz & Heger, Inc

ATC-58 Project Lead

2006 COSMOS Annual Meeting

Berkeley, California,

November 17, 2006

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Discussion itemsDiscussion items

ATC-58 project

Procedures for scaling ground motions! Method 1: geometric mean

!Method 2: spectrum-matching

! Method 3: Sa at T1! Method 4: amplitude scaling to spectral stripes

Performance assessment!

Intensity-based assessments! Scenario-based assessments

! Time-based assessments

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ATC-58 ProjectATC-58 Project

Next generation tools and

guidance for performance based

seismic assessment and design

! FEMA 273/356 (ATC-33 project)

! PEER research program

! Phase I: assessment tools (2009)

! Phase II: design tools (2014)

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ATC-58 ProjectATC-58 Project

Assessment options! Intensity: response spectrum

"Median response

! Scenario: [M, r] pair"Median response and dispersion

! Time-based: seismic hazard curve"Median responses and dispersions

Seismic hazard analysis

! USGS seismic hazard maps! PSHA

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Scaling procedures: method 1Scaling procedures: method 1

Amplitude scale a pair of motions to minimize thesum of the residuals between the target spectrumand the geometric-mean spectrum

Preserves both correlation between components of a

pair and irregular shape of spectra

0 1 2 3 4Period (sec)

0

0.5

1

1.5

2

2.5

Spectra

lacceleration

(g

EQ1

EQ2

Geometric mean

Target spectrum

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50 pairs of amplitude-scaled NF (25) and FF motions

Spectral shapes for the median and target spectra

Dispersion in spectral demand retained

Benchmark dataset (Bin 1)



0

1

2

3

4

Spectralacceleration

(g


0

1

2

3

4


(g

Median

16thand 84th

Target spectrum

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Spectrum-matching using RSPmatch

Bin 2 motions are spectrum-matched Bin 1 motions

Target spectra: median NF and FF spectra of Bin 1


0

0.5

1

1.5

2

2.5


(


0

0.5

1

1.5

2

2.5


(

Median, 16thand 84th

Bin 1

Bin 2

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Amplitude-scale individual ground motion records to atarget spectral acceleration at T1(Shome, Cornell, et al.)

0 0.5 1 1.5 2Period (sec)

0

1

2

3

4

Spe

ctralacceleration

(

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Sample spectral striping

! Computation at 1 second

! 5 stripes

!"=0.3g and #=0.4

0 0.2 0.4 0.6 0.8 1Spectral acceleration (g)

0

1

2

3

4

5

Probabilitydensityfunction

!=0.3g; "=0.4

0 0.2 0.4 0.6 0.8 1Spectral acceleration (g)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Cumulative

distributionfunction

!=0.3g; "=0.4

a.

b.

x1 x2 x3 x4 x5

0 0.5 1 1.5 2Period (sec)

0

0.2

0.4

0.6

0.8

1

Spectral

acceleration

(g)

c.

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Generate 11 spectral stripes using "and #; Bin 1 FF

Amplitude scale one ground motion, randomlyselected from Bin 1 FF, to one of the spectral stripesat the first mode period; repeat 11 times with

randomly selected motions


0

1

2

3

Spectra

lacceleration

(g) 11 spectral stripes

using !and "in Bin 1 motions

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Evaluation of method 2Evaluation of method 2

Nonlinear response analysis of bilinear oscillators

! Yield strength: infinity, 0.4W, 0.2W, 0.1W and 0.06W

! Underestimates median (nonlinear); dispersion is lost

0 0.4 0.8 1.2 1.6 2Period1(sec)

0

0.2

0.4

0.6

Peakdisplacement,Sd(

a. 84th, 50thand 16th

pers. of Sd, elasticb. 84th, 50thand 16th

pers. of Sd, Fy=20%Wc. 84th, 50thand 16th

pers. of Sd, Fy=6%W

0 0.4 0.8 1.2 1.6 2Period1(sec)

0

0.2

0.4

0.6

2 2.4 2.8 3.2 3.6 4Period2(sec)

0

0.2

0.4

0.6LL

L

Bin 2

yield displacement

Bin 1

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0 0.4 0.8 1.2 1.6 2Period1(sec)

0

0.2

0.4

0.6

Pe

akdisplacement,Sd(

a. 84th, 50thand 16th

pers. of Sd, elasticb. 84th, 50thand 16th

pers. of Sd, Fy=20%Wc. 84th, 50thand 16th

pers. of Sd, Fy=6%W

0 0.4 0.8 1.2 1.6 2Period1(sec)

0

0.2

0.4

0.6

2 2.4 2.8 3.2 3.6 4Period2(sec)

0

0.2

0.4

0.6L

L

L

Bin 3

yield displacement

Bin 1


! First mode period scaled motions across range of periods

! Unbiased estimate of median

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0 0.4 0.8 1.2 1.6 2Period1(sec)

0

0.2

0.4

0.6

!

(m)

a. !, elastic b. !, Fy=20%W c. !, Fy=6%W

0 0.4 0.8 1.2 1.6 2Period1(sec)

0

0.2

0.4

0.6

2 2.4 2.8 3.2 3.6 4Period2(sec)

0

0.2

0.4

0.65

Median of Bin 1

Distribution formedian estimateof Bin 4(16,50,84)



! 10,000 combinations of 11 seed motions from Bin 1

! Unbiased estimate of median

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c. !, Fy=6%Wb. !, Fy=20%Wa. !, elastic

0 0.4 0.8 1.2 1.6 2Period1(sec)

0

0.4

0.8

1.2

!

0 0.4 0.8 1.2 1.6 2Period1(sec)

0

0.4

0.8

1.2

2 2.4 2.8 3.2 3.6 4Period2(sec)

0

0.4

0.8

1.25



! 10,000 combinations of 11 seed motions from Bin 1

! Overestimates dispersion in displacement response

!of Bin 1Distribution for

estimate of !for Bin 4(16,50,84)


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Method 1: geometric mean! Pros: retains irregular spectral shape and

correlation between components; no need to

compute T1easy to implement;! Cons: finding a set of ground motions with a

median (or mean) spectrum that matches thetarget spectrum; treatment of dispersion

Method 2: spectrum matching

! Pros: no need to compute T1; easy to implement! Cons: underestimates median displacement

demand in highly nonlinear systems; greatlyreduces dispersion

Summary-1Summary-1

0 1 2 3 4

Period (sec)

0

0.5

1

1.5

2

2.5


(

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Method 3: Sa at T1! Pros: unbiased estimate of median demand; easy

to implement

! Cons: dispersion is lost for near-elastic systems;need to know T1

Method 4: Spectral-stripes

! Pros: unbiased median demand; conservatively

estimates dispersion! Cons: minor level of complexity; need to know T1

0 1 2 3 4

Period (sec)

0

0.5

1

1.5

2

2.5


(

Summary-2Summary-2

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Intensity-based assessmentIntensity-based assessment

Calculate loss given a response spectrum

Compute mediandisplacements and accelerationsonly; some dispersion retained

Hazard representation!

5% damped spectrum for horizontal shaking Scaling procedure! Amplitude scale a number (n) of recorded ground motions

(NF or FF) using Method 3: Sa at T1! Required number is a function of dispersion in the

displacement response given the scaling procedure,required accuracy of the estimate, and required confidencein the estimate

! For #=0.55, 75% confidence, 20% of median, 12 groundmotions required.

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Calculate a distribution of loss (median, fractiles)given an earthquake magnitude and distance

Compute the mediandisplacements andaccelerations and their dispersions

Hazard representation! Median spectral demand and dispersions in the demand

defined by a controlling [M, r] pair and an attenuationrelationship

Scaling procedure!

Generate 11 spectral curves based on median demands anddispersions

! Amplitude-scale 11 recorded ground motions, one per stripe(value of Sa) at T1

Scenario-based assessmentScenario-based assessment

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Time-based assessmentTime-based assessment

Establish distribution of annualized loss

Compute the mediandisplacements andaccelerations and their dispersions at selectedannual frequencies of exceedance

Hazard representation! Seismic hazard curves

Scaling procedure! Determine mean spectral ordinates at the selected

frequencies of exceedance and T1! Amplitude scale 12 recorded ground motions to the target

spectral ordinates using Method 3

! Series of intensity-based assessments

! Method 4 scaling could be used to capture dispersion(epistemic uncertainty) at each annual frequency ofexceedance

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Issues yet to be addressedIssues yet to be addressed

Multi-mode scaling rules! Mid-rise and high-rise buildings

! Nonstructural components and systems

Scaling of small AFE (0.0004), near-fault motions

! ATC-63 project recommendations Rotated geometric mean and max/min shaking

! USGS seismic hazard maps and correction factors

! BSSC Project 07

Forward rupture directivity

! BSSC Project 07! FN and FP motions

Three-components sets of acceleration histories

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AcknowledgmentsAcknowledgments

Robert Bachman

Craig Comartin

Allin Cornell

C.B. Crouse

Greg Deierlein

Robert Hanson

Stephen Harmesan Jon Heintz

John Hooper

Charles Kircher

E.V. Leyendecker

Nico Luco

Michael Mahoney

Andy Merovich

Jack Moehle Paul Somerville

Huang_2006 mio

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