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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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
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: Development of Next-Generation Performance-Based Seismic Design Guidelines
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: Development of Next-Generation Performance-Based Seismic Design Guidelines
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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
• 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)
Scaling procedures: method 1Scaling procedures: method 1
0 1 2 3 4Period (sec)
0
1
2
3
4
Sp
ectr
al a
ccel
erat
ion
(g )
0 1 2 3 4Period (sec)
0
1
2
3
4
Sp
ectr
al a
c ce l
e ra
t i on
(g)
Median
16th and 84th
Target spectrum
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
Scaling procedures: method 2Scaling procedures: method 2
• Spectrum-matching using RSPmatch• Bin 2 motions are spectrum-matched Bin 1 motions• Target spectra: median NF and FF spectra of Bin 1
0 1 2 3 4Period (sec)
0
0.5
1
1.5
2
2.5
Sp
ect
ral a
cce
lera
tion
(g
)
0 1 2 3 4Period (sec)
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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
Scaling procedures: method 3Scaling procedures: method 3
• 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)
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
Scaling procedures: method 4Scaling procedures: method 4
• 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.
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
Scaling procedures: method 4Scaling procedures: method 4
• 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 4Period (sec)
0
1
2
3
Sp
ect
ral a
cce
ler a
t ion
(g
) 11 spectral stripesusing θ and β in Bin 1 motions
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
Evaluation of method 3Evaluation of method 3
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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
Evaluation of method 4Evaluation of method 4
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)
• Nonlinear response analysis of bilinear oscillators Yield strength: infinity, 0.4W, 0.2W, 0.1W and 0.06W
10,000 combinations of 11 seed motions from Bin 1
Unbiased estimate of median
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
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
• Nonlinear response analysis of bilinear oscillators Yield strength: infinity, 0.4W, 0.2W, 0.1W and 0.06W
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)
Evaluation of method 4Evaluation of method 4
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
• 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 1 2 3 4Period (sec)
0
0.5
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Sp
ect
ral a
cce
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t ion
(g
)
0 1 2 3 4Period (sec)
0
0.5
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1.5
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2.5
Sp
ect
ral a
c ce
lera
tion
(g
)
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
• 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 1 2 3 4Period (sec)
0
0.5
1
1.5
2
2.5
Sp
ect
ral a
cce
ler a
t ion
(g
)
0 1 2 3 4Period (sec)
0
0.5
1
1.5
2
2.5
Sp
ect
ral a
c ce
lera
tion
(g
)
Summary-2Summary-2
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
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.
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
• 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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
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
ATC-58: Development of Next-Generation Performance-Based Seismic Design Guidelines
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