14wcee keynote presentation

7/28/2019 14WCEE Keynote Presentation

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J ack MoehlePacific Earthquake Engineering Research CenterUniversity of California, Berkeley

with contributions fromYousef Bozorgnia, Tony Yang, PEER/BerkeleyRon Klemencic, MKA Seattle

J oe Maffei, Rutherford & ChekenePaul Somerville, SCEC/URS

J ohn Wallace, PEER/UCLA

Performance-BasedSeismic Design of

Tall Buildings in the

United States


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Base

Shear

Deformation

DamageThreshold

CollapseOnset

OPEN

OPEN

OPEN

Performance-based seismic design

Performance LevelsServiceability Safety

Shaking LevelInfrequent Very rare


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OPEN

OPEN

OPEN

Performance-based seismic design

Performance LevelsServiceability SafetyToday

Downtime, days0 1 7 30 180

Casualty rate0.0 0.0001 0.001 0.01 0.25

Tomorrow$, % replacement0 25% 50% 100%

Base

Shear

DamageThreshold

CollapseOnset

Deformation


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Tall buildings

(proposed, approved, or under construction, at last count)Over 75m: San Francisco 38; Los Angeles 61; Seattle

Steve Boland, 2006


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The new generation oftall buildings

Whats different about them? High-performance materials andsystems

Framing systems not satisfying code

prescriptions undefined systems

defined systems beyond permitted heightlimits

MKA


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MKA


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MKA


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MKA


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MKA


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104.11 Alternative materials, design and methods of construction

and equipment. The provisions of this code are not intended to prevent

the installation of any material or to prohibit any design or method of

construction not specifically prescribed by this code, provided that any

such alternative has been approved. An alternative material, design or

method of construction shall be approved where the building official

finds that the proposed design is satisfactory and complies with the intentof the provisions of this code, and that the material, method or work

offered is, for the purpose intended, at least the equivalent of that

prescribed by this code in quality, strength, effectiveness, fire resistance,

durability and safety.


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Building review and approval Peer review

Three-member panel with relevant expertise

Submittal requirements

Seismic design criteria Computer models

Design and verification results

Project specs and construction drawings


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Seismic Design Criteria Earlier approach

Satisfy all coderequirements, withlimited exceptions

Code enhancements

explicit capacity design

performance verificationusing nonlinearanalysis

detailing enhancements

More recent approach

Establish performanceobjectives

explicit capacitydesign as appropriate

performanceverification bynonlinear dynamic

analysis detail as required to

ensure performance


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Seismic performance objectives

after Vision 2000, SEAOC


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None/Slight Moderate Extensive Complete Collapse

Level A 20 15 4 1 0

Level B 19 9 7 4 1

Level C 12 6 9 9 4

Expected No. of Bldgs in each Structural Damage StateHypothetical

Performance

Performance objectives questionGiven 40 tall buildings in a city.Very rare earthquake.

What do you think of this performance scenario?

Holmes et al, 2008


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URS

Seismic

hazardanalysis


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Probabilistic

seismic hazardanalysis

0 2 4 6 8 10Period, sec

Pseudo

Acceleration,g

2.5

2.0

1.5

1.0

0.5

0.00 2 4 6 8 10Period, sec

Pseudo

Acceleration,g

2.5

2.0

1.5

1.0

0.5

0.0

2% in 50 yr UHS2% in 50 yr UHS2% in 50 yr UHS


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Selection and scaling of ground

motions

TARGET


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T1

0 2 4 6 8 10

Period, sec

PseudoAc

celeration,g

2.5

2.0

1.5

1.0

0.5

0.0

2% in 50 yr UHS

2% in 50 yr M6.5 Scenario

Scenario spectrum


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Nonlinear analytical models

FloorNumber

Lateral

system

Gravity-only

system-0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15

-4000

-3000

-2000

-1000

0

1000

2000

3000

Analytical

Experimental

Link beam

Momen

t

Rotation

Bounding Analysis0.25-1.0Gc0.1-0.5Gc


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Model sensitivity: Wall shear

0

10

20

30

40

FloorLevel

-20000-1000001000020000

Wall Shear

Case 1

Case 2

Case 3Case 4

No Factors

ATC 72 (Wallace), 2008


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20000100000

Strong hinge

Intermediate

Intermediate

Weak hinge

Model sensitivity: Wall moment

0

10

20

30

60

50

40

FloorLevel

Moment

intended

yield hinge


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Modeling assumptions

0

10

20

30

40

FloorLevel

-30000 -20000 -10000 0 10000 20000 30000

North South Force (K)

Fiber Hinge

Fiber all

FloorLevel

0

10

20

30

40

FloorLevel

-30000 -20000 -10000 0 10000 20000 30000

North South Force (K)

Fiber Hinge

Fiber all

FloorLevel

0

10

20

30

40

-20000000 0 20000000

Moment about East West axis(K-in)

Fiber Hinge

Fiber all

0

10

20

30

40

-20000000 0 20000000

Moment about East West axis(K-in)

Fiber Hinge

Fiber all

ATC 72 (Wallace), 2008


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Damping

ATC 72 (Deierlein), 2008, after data from Goel and Chopra, 1997


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Calculated dynamic response

Yan

g,

2007


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DBE

CMS, T2

CMS, T1

CMS, T3

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 1 2 3 4 5 6 7 8

Period, sec

SpectralAc

celeration,g

T3

T2

T1

DBE

CMS, T2

CMS, T1

CMS, T3

DBE

CMS, T2

CMS, T1

CMS, T3

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0 1 2 3 4 5 6 7 80 1 2 3 4 5 6 7 8

Period, sec

Scenario spectra

Baker and Yang, 2008


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(b) Peak building responses

Wall shears and moments

0 0.5 1.0B5

L1

L6

L11

L17

L22

L27

L32

L37

L42

Wall Shear

FloorNumber

0

Wall Moment

0 0.5 1.00 0.5 1.0B5

L1

L6

L11

L17

L22

L27

L32

L37

L42

Wall Shear

FloorNumber

0

Wall Moment

0 0.5 1.0

DBE

CMS, T2

CMS, T1

CMS, T3

DBE

CMS, T2

CMS, T1

CMS, T3

DBE

CMS, T2

CMS, T1

CMS, T3

Baker and Yang, 2008


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Design values?

BASE

13th

ROOF

(a) Building elevation (b) Summary of results

Roofdrift, ft Wallbaseshear, k

Wallmoment at13th floor,1000 x k-ft

Minimum

MaximumMean (m)

m +c.o.v.

Nonlinearstatic

2.1

6.74.25.40.23

7600

2970015500222000.43

5500

513

108090010900.21

760

after Maffei


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a design philosophy in rare earthquake ground shaking

there should be no more than a 50% chancethat demands will exceed capacities forductile failure modes, and

the chance of experiencing a nonductilefailure mode should be less.


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Structural wall tests

Berkeley and PCA tests ca 1970s and 1980sCTL 1980


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Flexural assessment

+2.0%

-0.015

-0.01

-0.005

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0 200 400 600 800 1000 1200

Distance from the left end [mm]

strains

Test Results+2.0%

Wallace 2007

Fiber model

T i l fl


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Typical flexure

verification

Core walltension strains


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Shear-compression failure

Corley, Fiorato, Oesterle, ACI SP 72, 1981CTL 1980


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Design for brittle failure modes Design demands shall consider

dispersion of calculated responses. Design strengths shall be based on

specified materials properties with

strength reduction factors per the code.

R =capacityQ =demand

Y =R - Q

Y

Y

Y = R - Q

Frequency

P[(Y = R - Q) < 0]

= shaded area

YY

Y

Y = R - Q

Frequency

P[(Y = R - Q) < 0]

= shaded area

R =capacityQ =demand

Y =R - Q

Y

Y

Y = R - Q

Frequency

P[(Y = R - Q) < 0]

= shaded area

YY

Y

Y = R - Q

Frequency

P[(Y = R - Q) < 0]

= shaded area

Y

Y

Y = R - Q

Frequency

P[(Y = R - Q) < 0]

= shaded area

YY

Y

Y = R - Q

Frequency

P[(Y = R - Q) < 0]

= shaded area

Vn Vu

mean +


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Outrigger Forces1.2D + 1.6L

Moreactions

(L reduced)

moments(L not reduced)

Gravity

1.0D + 0.1L

MoM

o

/4

Seismic


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Calculated outrigger axial forces

0 100 200 300 400 500 600 700 800 900B5

1

6

11

17

22

27

32

37

42

axial force [kips]

Floor

number[-]

Mean

Mean + stddata

Yang, 2008

Slab-wall connection


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Slab-wall connection

performance

Klemencic, Frye, Hurtado, Moehle, PCI, 2006

i kConfine diagonals


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Link

beams

g

Confine section

ACI 318, 2008


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Diagonally reinforced link beams

-4.32 -2.16 0 2.16 4.32Relative Displacement (in)

-200

-100

0

100

200

LateralLoad(k)

-0.12 -0.06 0 0.06 0.12

Drift (% Rotation)

ln/h = 2.4

Diagonal (B2)

Full (B1)

Rotation = 0.06

Wallace, 2007

B kli t i d b d


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Buckling-restrained braces and

steel plate shear walls

LA Live!, Los Angeles


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WAMU Center, Seattle


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One Rincon Hill, San Francisco


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February 2005


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February 2005


March 2005


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March 2005


April 2005


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April 2005


May 2005


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May 2005


J une 2005


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J une 2005


J uly 2005


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J uly 2005


August 2005


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August 2005


September 2005


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September 2005


October 2005


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October 2005


November 2005


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November 2005


December 2005


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December 2005


J anuary 2006


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J anuary 2006


February 2006


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February 2006


March 2006


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LA Convention Center Park 5th Pershing Square

76 stories

11 ft/story

2000 Third, Seattle


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Millennium Tower, San Francisco


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LA Center, Los Angeles


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Grand Avenue, Los Angeles


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Summary New generation of tall

buildings Performance-based design

Opportunities andchallenges

Grand Avenue, Los Angeles

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