dhs/fema atc-58 project selection and scaling of …€¦ · · 2012-12-02atc-58: development of...

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

DHS/FEMA ATC-58 ProjectDHS/FEMA ATC-58 ProjectSelection and Scaling of GroundSelection and Scaling of Ground

MotionsMotionsYin-Nan Huang

University at BuffaloAndrew Whittaker, S.E.,

University at BuffaloATC-58 SPP Team LeadRon Hamburger, S.E.

Simpson, Gumpertz & Heger, IncATC-58 Project Lead

2006 COSMOS Annual MeetingBerkeley, California,November 17, 2006


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


ATC-58 ProjectATC-58 Project

• Next generation tools andguidance for performance basedseismic assessment and design FEMA 273/356 (ATC-33 project)

PEER research program

Phase I: assessment tools (2009)

Phase II: design tools (2014)


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


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 apair and irregular shape of spectra

0 1 2 3 4Period (sec)

0

0.5

1

1.5

2

2.5

Sp

ectr

al a

cce

l er a

ti on

( g)

EQ1

EQ2

Geometric mean

Target spectrum


• 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

Sp

ectr

al a

ccel

erat

ion

(g )


0

1

2

3

4

Sp

ectr

al a

c ce l

e ra

t i on

(g)

Median

16th and 84th

Target spectrum



• 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

Sp

ect

ral a

cce

lera

tion

(g

)


0

0.5

1

1.5

2

2.5

Sp

ect

ral a

cce

ler a

t ion

(g

)

Median, 16th and 84th

Bin 1

Bin 2



• 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

4S

pe

ctra

l ac c

el e

r at io

n (

g)



• Sample spectral striping Computation at 1 second

5 stripes♣ θ=0.3g and β=0.4

0 0.2 0.4 0.6 0.8 1Spectral acceleration (g)

0

1

2

3

4

5P

rob

ab

ility

de

ns i

t y f

un

ctio

n

θ=0.3g; β=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

Cum

ulat

ive

dist

r ibu t

i on

func

ti on

θ=0.3g; β=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

Sp

ect

ral a

cce

ler a

tion

(g

) c.



• Generate 11 spectral stripes using θ and β; Bin 1 FF• Amplitude scale one ground motion, randomly

selected from Bin 1 FF, to one of the spectral stripesat the first mode period; repeat 11 times withrandomly selected motions


0

1

2

3

Sp

ect

ral a

cce

ler a

t ion

(g

) 11 spectral stripesusing θ and β in Bin 1 motions


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

Pe

ak d

isp

lace

me

n t,

Sd

( m)

a. 84th, 50th and 16th

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

pers. of Sd, Fy=20%Wc. 84th, 50th and 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 2

yield displacement

Bin 1



0 0.4 0.8 1.2 1.6 2Period1 (sec)

0

0.2

0.4

0.6

Pe

ak d

isp

lace

me

nt,

Sd

( m)

a. 84th, 50th and 16th

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

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

• Nonlinear response analysis of bilinear oscillators First mode period scaled motions across range of periods

Unbiased estimate of median



0 0.4 0.8 1.2 1.6 2Period1 (sec)

0

0.2

0.4

0.6

θ (

m)

a. θ, elastic b. θ, Fy=20%W c. θ, 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

0.6µ<5µ>5

Median of Bin 1

Distribution for median estimateof Bin 4(16,50,84)


10,000 combinations of 11 seed motions from Bin 1

Unbiased estimate of median


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

0 0.4 0.8 1.2 1.6 2Period1 (sec)

0

0.4

0.8

1.2

β

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

1.2µ<5µ>5


10,000 combinations of 11 seed motions from Bin 1

Overestimates dispersion in displacement response

β of Bin 1

Distribution forestimate of βfor Bin 4(16,50,84)



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

correlation between components; no need tocompute T1 easy to implement;

Cons: finding a set of ground motions with amedian (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

0.5

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1.5

2

2.5

Sp

ect

ral a

cce

ler a

t ion

(g

)


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0.5

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2.5

Sp

ect

ral a

c ce

lera

tion

(g

)


• Method 3: Sa at T1

Pros: unbiased estimate of median demand; easyto 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

0.5

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2.5

Sp

ect

ral a

cce

ler a

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(g

)


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Sp

ect

ral a

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(g

)

Summary-2Summary-2


Intensity-based assessmentIntensity-based assessment

• Calculate loss given a response spectrum• Compute median displacements and accelerations

only; 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 thedisplacement response given the scaling procedure,required accuracy of the estimate, and required confidencein the estimate

For β=0.55, 75% confidence, ±20% of median, 12 groundmotions required.


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

• Compute the median displacements 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 and

dispersions Amplitude-scale 11 recorded ground motions, one per stripe

(value of Sa) at T1

Scenario-based assessmentScenario-based assessment


Time-based assessmentTime-based assessment

• Establish distribution of annualized loss• Compute the median displacements and

accelerations 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 targetspectral 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


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


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

dhs/fema atc-58 project selection and scaling of …€¦ · · 2012-12-02atc-58: development of...

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