1

Innovations in Innovations in Earthquake Resistant Earthquake Resistant

Steel StructuresSteel Structures

Michel BruneauDirector, MCEERProfessor, CSEE

University at Buffalo

Selected Recent InnovationsSelected Recent Innovations

Expanding range of applicability of a number of new and emerging structural steel systems that can provide effective seismic performance.

Buckling Restrained Braced Designed to meet Structural Fuse objectives

Rocking braced frames.Tubular Eccentrically Braced FramesSteel Plate Shear Walls

AcknowledgmentsAcknowledgmentsPh.D. Students:

Bing Qu – Seismic Performance of Buildings with Steel Plate Shear WallsMichael Pollino – Rocking Steel Framed SystemsJeffrey Berman – Seismic Retrofit of Large Bridges Braced BentRamiro Vargas – Enhancing Resilience using Passive Energy Dissipation SystemsDarren Vian – Passive Energy Dissipation using Metallic In-fillsShuichi Fujikura – Multi-Hazard Resilient Bridges

M.Sc. Students: Ronny Purba – Design of Perforated Steel Plate Shear WallsJeffrey Berman – Thin Steel Infill Walls as Passive Energy Dissipators for the Seismic Retrofit of Hospitals

Post-Doc: Gordon Warn – Blast Resistance of Steel Plate Shear WallsFunding to MCEER from:

National Science Foundation Federal Highway Administration

Buckling Restrained Braces in Buckling Restrained Braces in Structural Fuse ApplicationStructural Fuse Application

Structural FusesStructural FusesEarthquake-resistant design has long relied on hysteretic energy dissipation to provide life-safety level of protectionAdvantages of yielding steel

Stable material properties well known to practicing engineersNot a mechanical device (no special maintenance)Reliable long term performance (resistance to aging)

For traditional structural systems, ductile behavior achieved by stable plastic deformation of structural members = damage to those membersIn conventional structural configurations, serves life-safety purposes, but translates into property loss, and need substantial repairsResearchers have proposed that hysteretic energy dissipation should instead occur in “disposable”structural elements (i.e., structural fuses)

Roeder and Roeder and PopovPopov (1977)(1977)

Ductile seismic behaviorConcentrating energy dissipation in special elements + capacity designLinks not literally disposable

““Ductile FuseDuctile Fuse””

Eccentrically Braced FrameEccentrically Braced Frame

Other studies:Fintel and Ghosh (1981)Aristizabal-Ochoa (1986)Basha and Goel (1996)Carter and Iwankiw (1998)Sugiyama (1998)Rezai et al. (2000)

2

Wada et al. (1992)Wada et al. (1992)DamageDamage--controlled or controlled or DamageDamage--tolerant Structurestolerant Structures

Other studies:Connor et al. (1997)Shimizu et al. (1998)Wada and Huang (1999)Wada et al. (2000)Huang et al. (2002)

Ductile elements were used to reduce inelastic deformations of the main structureConcept applied to high rise buildings (T > 4 s)

Ground Motion, üg(t)

mass, m

frame, fbraces, b

structural fuse, d

Benefits of Structural Fuse Concept:Benefits of Structural Fuse Concept:

Seismically induced damage is concentrated on the fusesFollowing a damaging earthquake only the fuses would need to be replacedOnce the structural fuses are removed, the elastic structure returns to its original position (self-recentering capability)

Δya Δyf u

KfKa

K1

αK1 = Kf

Vyf

Vyd

Vy

Vp

V

Frame

Structural Fuses

Total

αμmax

0.05

0.25

0.50

.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0

.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0.0.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0

.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0

.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0

.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0

.0

.2

.4

.6

.8

1.0

.0 .2 .4 .6 .8 1.0

10 5 2.5 1.67

Frame Damping System Total

V/Vp

u/Δyf

Structural Fuses

μμ ff== uum

axmax

// ΔΔyfyf

T=T=

ηη=0.2=0.2

ηη=1.0=1.0

αα= 0.05= 0.05

μμmaxmax = 10= 10Drift Limit (NL THA)Drift Limit (NL THA)Drift Limit (Suggested)Drift Limit (Suggested)

System PropertiesSystem Properties

IB, ZB

IC IC

L

H

Bare FrameBare Frame

IB, ZB

IC

L

HIC

θ θ

Ab Ab

BRBsBRBsIB, ZB

IC IC

L

H

θ θ

Ab Ab

N plates

TT--ADASADAS

IB, ZB

IC IC

L

H

θ θ

Ab Ab

Shear Panel

Shear PanelShear Panel

h

b

t

h

w

t

bftf

3

Model withModel withNippon Steel Nippon Steel BRBsBRBs

Eccentric GussetEccentric Gusset--PlatePlate

Test 1 Test 1 (PGA = 1g)(PGA = 1g)

Test 1Test 1First Story BRBFirst Story BRB

-40

-30

-20

-10

0

10

20

30

40

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

Axial Deformation (in)

1st S

tory

Axi

al F

orce

(kip

s)

Test 1 (Nippon Steel BRB Frame)Test 1 (Nippon Steel BRB Frame)First Story Columns ShearFirst Story Columns Shear

-100

-75

-50

-25

0

25

50

75

100

-5 -4 -3 -2 -1 0 1 2 3 4 5

Inter-Story Drift (mm)

1st S

tory

Col

umns

She

ar (k

N)

Static Test Static Test -- Nippon Steel Nippon Steel BRBsBRBsNote: Replacement is to reNote: Replacement is to re--center the building center the building

(not due to BRB fracture life)(not due to BRB fracture life)

4

Rocking Trusses Rocking Trusses (Rocking Braced Frames)(Rocking Braced Frames)

Controlled Rocking/Energy Controlled Rocking/Energy Dissipation SystemDissipation System

Retrofitted Tower

Absence of base of leg connection creates a rocking bridge pier system partially isolating the structure

Installation of steel yielding devices (buckling-restrained braces) at the steel/concrete interface controls the rocking response while providing energy dissipation

Existing Rocking BridgesExisting Rocking BridgesSouth Rangitikei Rail Bridge Lions Gate Bridge North Approach

Static, Hysteretic Behavior of Controlled Static, Hysteretic Behavior of Controlled Rocking PierRocking Pier

Device Response

FPED=0FPED=w/2

General Design Constraints for General Design Constraints for Controlled Rocking SystemControlled Rocking System

(1) Deck-level displacement limits need to be established on a case-by-case basis

Maintain pier stabilityBridge serviceability requirements

(2) Strains on buckling-restrained brace (uplifting displacements) need to be limited such that it behaves in a stable, reliable manner(3) Capacity Protection of existing, vulnerable resisting elements considering 3-components of excitation and dynamic forces developed during impact and uplift(4) Allow for self-centering of pier

-1.5

-1

-0.5

0

0.5

1

1.5

-5 -3 -1 1 3 5

Δ/Δy

P/P y

Static Horizontal Response

Dynamic Response

(3) Capacity Protection (cont.)(3) Capacity Protection (cont.)

An increase from the static response has been observed due to dynamic excitation of vertical modes of vibration even when subjected solely to horizontal base accelerations

5

1

mm

2

mm

3

mm

4

mm

4 6

mm

mm

5

mm

7

m

m

ΣM=0

VelocityControl impact energy to foundation and impulsive loading on tower legs by limiting velocity

⇒

Displacement DuctilityLimit μL of specially detailed, ductile “fuses”

⇒

β<1⇒ Inherent re-centering (Optional)

Limit forces through vulnerable members using structural “fuses”

Acceleration⇒

Design ProcedureDesign Procedure

Design ConstraintsDesign Chart:

0 100 200 300 4000

2

4

6

8

10

constraint1constraint2constraint3constraint4constraint5

h/d=4

Lub (in.)

Aub

(in2

)

Lub

A ub

Experimental TestingExperimental TestingArtificial Mass Simulation Scaling Procedure

λL>5 (Crane Clearance)λA=1.0 (1-g Field)Wm=70kN (We=76kN)Tom=0.34sec (Toe=0.40sec)

Loading SystemPhase I

5DOF Shake TablePhase II

6DOF Shake Table

Δ

λL=5h/d=4.1

λt=2.26.1m

1.5m

Synthetic EQ 150% of DesignFree Rocking

Synthetic EQ 150% of DesignTADAS Case ηL=1.0 Synthetic EQ 150% of Design – Free Rocking

6

Synthetic EQ 175% of Design - Viscous Dampers

Eccentrically Braced Frames Eccentrically Braced Frames with Tubular Linkswith Tubular Links

b

dtf

tw

Fyw

Fyf

b

dtf

tw

Fyw

Fyf

b

dtf

tw

Fyw

Fyf

Tubular Eccentrically Braced FrameTubular Eccentrically Braced Frame

EBFs with wide-flange (WF) links require lateral bracing of the link to prevent lateral torsional bucklingLateral bracing is difficult to provide in bridge piersDevelopment of a laterallystable EBF link is warrantedConsider rectangular cross-section – No LTB

ProofProof--ofof--Concept TestingConcept Testing

ProofProof--ofof--Concept TestingConcept Testing Finite Element Modeling of Finite Element Modeling of ProofProof--ofof--Concept TestingConcept Testing

Hysteretic Results for Refined ABAQUS Model and Proof-of-Concept Experiment

7

Link Testing Link Testing –– ResultsResultsLarge Deformation Cycles of Specimen X1L1.6

Design SpaceDesign SpaceStiffened LinksUnstiffened Links

ρ

ρ = 1.6yfFE0.64

ftb

ywFE1.67

ywFE0.64

wtd

Steel Plate Shear Walls Steel Plate Shear Walls

Steel Panel Shear Walls (SPSW)Steel Panel Shear Walls (SPSW)

Lateral force-resisting system New or retrofit constructionThin steel panel added as an infill to a building’s structural frameIncreases stiffness and strength

Increased usage in Asia and North America in recent years

Building frame with SPSW

AISC Guide Design of SPSWAISC Guide Design of SPSW((SabelliSabelli and Bruneau 2006)and Bruneau 2006)

Review of implementations to dateReview of research resultsDesign requirements and processDesign examples

Region of moderate seismicityRegion of high seismicity

Other design considerations (openings, etc.)

Examples of ImplementationExamples of Implementation(Canada)(Canada)

Courtesy Louis Crepeau, Groupe Teknika, Montreal, Canada

8

Examples of ImplementationExamples of Implementation(Mexico)(Mexico)

Courtesy Martinez Romero, Mexico

Examples of ImplementationExamples of Implementation(USA)(USA)

Courtesy John Hooper, Magnusson-Klemencic Associates, Seattle

Examples of ImplementationExamples of Implementation(USA)(USA)

Courtesy Matthew Eatherton – GFDS Engineers San Francisco, CA

Example of Implementation Example of Implementation (USA) (USA) –– Hospital RetrofitHospital Retrofit

Courtesy Jay Love, Degenkolb Engineers, San Francisco

Bottom story “anchor” beam

Top story “anchor” beam

Inte

rmed

iate

bea

ms

Panel

TFAForce

s

SPSW Infillpanel (TYP)

Background of SPSW DesignBackground of SPSW Design Diagonal tension in steel plate Diagonal tension in steel plate shear wall web plateshear wall web plate

diagonalfolds

tensilestresses

lateralload

α

angle ofinclination

HBE

HBE

VBE Web plate

9

Analogy to TensionAnalogy to Tension--only only Braced FrameBraced Frame

Flat bar braceVery large brace slenderness (e.g. in excess of 200)

V

Pinched hysteretic curvesIncreasing drift to dissipate further hysteretic energyNot permitted by AISC Seismic ProvisionsPermitted by CSA-S16 within specific limits of application

Analogy to TensionAnalogy to Tension--only only Braced FrameBraced Frame

Steps to “transform”into a SPSW1) Replace braces by infill plate (like adding braces)

V

Anchor Beam

Analogy to TensionAnalogy to Tension--only only Braced FrameBraced Frame

Steps to “transform”into a SPSW1) Replace braces by infill plate (like adding braces)2) For best seismic performance, fully welded beam-column connections

V

EndEnd--ResultResult

Cyclic (Seismic) behavior of SPSWSum of

Fuller hysteresisprovided by moment connectionsStiffness and redundancy provided by infill plate

V

Bottom story “anchor” beam

Top story “anchor” beam

Inte

rmed

iate

bea

ms

Panel

TFAForce

s

SPSW Infillpanel (TYP)

Background of SPSW DesignBackground of SPSW Design

Similar to Plate Girder behavior but…

10

ButBut……SPSWsSPSWs are NOT Plate Girdersare NOT Plate Girders

Berman, J., Bruneau, M., (2004). “Steel Plate Steel Plate Shear Walls are not Plate GirdersShear Walls are not Plate Girders”, AISC Engineering Journal.Seismic design provisions specifically developed for SPSW must provide:

Design procedure (and, in commentary, modeling guidance) based onCapacity design approach with clear hierarchy of yielding

Plastic Analysis ApproachPlastic Analysis Approach

Yielding stripsPlastic Hinges

For designstrength, neglectplastic hingescontribution

hM

LtFV py

⋅+⋅⋅⋅⋅=

42sin

21 α

Berman/Bruneau June 12 2002 TestBerman/Bruneau June 12 2002 Test

L/tw = 3740h/L = 0.5(centerline

dimensions)

Example of Structural FuseExample of Structural Fuse

-3 -2 -1 0 1 2 3Drift (%)

-600

-400

-200

0

200

400

600

Bas

e S

hear

(kN

)

Specimen F2Boundary Frame

-3 -2 -1 0 1 2 3Drift (%)

-600

-400

-200

0

200

400

600

Base

She

ar (k

N)

From Driver et. Al (1997)

Accuracy of modelAccuracy of model

11

Steel Plate Shear Walls (SPSW)Steel Plate Shear Walls (SPSW)

Roofbeam

Foundationbeam

Intermediatebeams

HorizontalBoundaryElements(HBEs)

Columns(Vertical

BoundaryElements,

VBEs)

Steelplates

VBE Design ProcedureVBE Design ProcedureSpecimen P at 3.0% DriftSpecimen P at 3.0% Drift

Specimen CR at 4.0% DriftSpecimen CR at 4.0% Drift

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

-80 -60 -40 -20 0 20 40 60 80Displacement (mm)

Tota

l For

ce (k

N)

-4% -3% -2% -1% 0% 1% 2% 3% 4%

Specimen Specimen CRCR

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

-80 -60 -40 -20 0 20 40 60 80Displacement (mm)

Tota

l For

ce (k

N)

-4% -3% -2% -1% 0% 1% 2% 3% 4%

Specimen Specimen S2S2

-2000

-1500

-1000

-500

0

500

1000

1500

2000

-80 -60 -40 -20 0 20 40 60 80Displacement (mm)

Tota

l For

ce (k

N)

-4% -3% -2% -1% 0% 1% 2% 3% 4%

Specimen PSpecimen P

12

Single Strip InvestigationSingle Strip Investigation(building blocks of the full infill)(building blocks of the full infill)

RF Model: Deformed Shape (1)RF Model: Deformed Shape (1)At monitored strain At monitored strain εεmaxmax = 20%, D = 200 mm (D/S= 20%, D = 200 mm (D/Sdiagdiag = 0.471)= 0.471)

Deformation Scale Factor = 1.0

RF Model: Deformed Shape (2)RF Model: Deformed Shape (2)At monitored strain At monitored strain εεmaxmax = 20%, D = 200 mm (D/S= 20%, D = 200 mm (D/Sdiagdiag = 0.471)= 0.471)

Deformation Scale Factor = 2.0

• Maximum peak: 67.9 mm

• Maximum valley: -67.5 mm

• Between holes: 60.4 mm

RF Model: Typical Panel ResultsRF Model: Typical Panel ResultsAt monitored strain At monitored strain εεmaxmax = 20%, D = 200 mm (D/S= 20%, D = 200 mm (D/Sdiagdiag = 0.471)= 0.471)

Maximum In-Plane Principal Strain Contours

Uniform Distributed Strip Axial Strain Uniform Distributed Strip Axial Strain εεunun versus Perforation Ratio versus Perforation Ratio D/D/SSdiagdiag Infill Shear Strength: RF ModelInfill Shear Strength: RF Model

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0D/Sdiag

Vyp.

perf

/ Vyp

Predicted (Eq. 4.3)γ = 5%γ = 4%γ = 3%γ = 2%γ = 1%Linear Reg.

51.5%

ypperfyp VSdiag

DV ⋅⎥⎦⎤

⎢⎣⎡ −= 1. α

α = 0.7correction factor:

13

Steel Plate Shear Walls (SPSW)Steel Plate Shear Walls (SPSW)

Roofbeam

Foundationbeam

Intermediatebeams

HorizontalBoundaryElements(HBEs)

Columns(Vertical

BoundaryElements,

VBEs)

Steelplates

Specimen before TestsSpecimen before Tests

Experimental ProgramExperimental Program

Phase I: Pseudo-dynamic load to an earthquake having a 2% in 50 years probability of occurrence. (Chi_Chi_CTU082EW--2╱50 PGA=0.67g)Cut-out and replace webs at both levelsPhase II: Repeat of pseudo-dynamic load to an earthquake having a 2% in 50 years probability of occurrence.Subsequently cyclic load to failure.

Web replacementWeb replacement

Buckled web plate from first pseudo-dynamic test cut out and new web plate welded in place

PseudoPseudo--dynamic Test (contdynamic Test (cont’’d)d) PseudoPseudo--dynamic Test (contdynamic Test (cont’’d)d)

1st story 2nd story

Specimen after the maximum peak drifts of 2.6% at lower story and 2.3% at upper story in pseudo-dynamic test.

14

Subsequently Cyclic Test Subsequently Cyclic Test Subsequently Cyclic Test (contSubsequently Cyclic Test (cont’’d)d)Failure Modes: Failure occurred in the load transfer mechanism, i.e. through the upper concrete slab of the specimen.

Severe plate damage and intermediate beam damage also occurred at drifts between 2.5% and 5%

Subsequently Cyclic Test (contSubsequently Cyclic Test (cont’’d)d)

Specimen after interstory drift of 5%

Severe plate damage and intermediate beam damage also occurred at drifts between 2.5% and 5%

1st Story after interstory drift of 5%

2nd story after interstory drift of 5%

Subsequently Cyclic Test (contSubsequently Cyclic Test (cont’’d)d)

Fractures close to RBS connection at the north end of intermediate beam after interstory drift of 5%

Subsequently Cyclic Test (contSubsequently Cyclic Test (cont’’d)d)

Fractures close to RBS connection at the south end of intermediate beam after interstory drift of 5%

Subsequently Cyclic Test (contSubsequently Cyclic Test (cont’’d)d)

15

Simulation of PseudoSimulation of Pseudo--dynamic Testdynamic TestSimulation of PseudoSimulation of Pseudo--dynamic Testdynamic Test

-150

-100

-50

0

50

100

150

200

250

0.00 10.00 20.00 30.00 40.00 50.00Time (Sec)

2F D

ispl

acem

ent (

mm

)

-150

-100

-50

0

50

100

150

200

250

0.00 10.00 20.00 30.00 40.00 50.00Time (Sec)

1F D

ispl

acem

ent (

mm

)

Strong Ground Motion

Strong Ground Motion

Simulation of PseudoSimulation of Pseudo--dynamic Testdynamic Test

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

-3 -2 -1 0 1 2 3DRIFT-1F (%)

STOR

Y SH

EAR-

1F (k

N)

STRIP-25

PSEUDO-DYNAMIC TEST

-5000

-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

-3 -2 -1 0 1 2 3DRIFT-2F (%)

STOR

Y SH

EAR-

2F (k

N)

STRIP-25

PSEUDO-DYNAMIC TEST

Simulation of Monotonic PushoverSimulation of Monotonic Pushover

-6000

-4000

-2000

0

2000

4000

6000

-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6DRIFT-1F (%)

STOR

Y SH

EAR-

1F (k

N)

3D-SHELL

Cy clic Test

-6000

-4000

-2000

0

2000

4000

6000

-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6DRIFT-2F (%)

STOR

Y SH

EAR-

2F (k

N)

3D-SHELL

Cy clic Test

Simulation of Monotonic PushoverSimulation of Monotonic PushoverPlastic Analysis ApproachPlastic Analysis Approach

Yielding stripsPlastic Hinges

For designstrength, neglectplastic hingescontribution

hM

LtFV py

⋅+⋅⋅⋅⋅=

42sin

21 α

16

Plastic Strength of SPSWPlastic Strength of SPSW

Plastic strength of uniformly yielded SPSW (Berman and Bruneau, 2003)

( ) ( )11 0 1

Contribution of HBE Contribution of Infill Panels

1 sin(2 )2i i

n n n

i i pl pr wi wi yp i ii i i

F h M M t t F LH α+= = =

= + + −∑ ∑ ∑1442443 1444442444443

Plastic strength of SPSW system includes contributions of infill panels and boundary frame. AISC Seismic Provisions assumes 100% of story shear is resisted by infill panel.

Single Story SPSW ExampleSingle Story SPSW ExampleDesign

L

α

h

Force assigned to infill panel

( )1 sin 22design yp wV f t Lhκ α⋅ =

Contribution of HBEContribution of Infill Panels

1 sin(2 )2plastic pl pr yp wV h M M f t Lh α⋅ = + +

14243 144424443

Capacity design of HBE (Darren and Bruneau, 2005) 2 2

2

cos 14 1 1

ypwb

yb

fL tZf

α

β

⋅ ⋅= ⋅ ⋅

+ −

Plastic strength of SPSW (Berman and Bruneau, 2003)

Design

L

α

h

Single Story SPSW ExampleSingle Story SPSW ExampleSingle Story SPSW ExampleSingle Story SPSW Example

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1κ

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

V pla

stic

/ Vde

sign

L/h=0.8L/h=1.00L/h=1.5L/h=2L/h=2.5

Overstrength from capacity design

Balance point

Design force to be assigned to boundary moment frame

45α = o

1.0β =

1

2

112 1 1

balanceLh

βκβ

−⎡ ⎤

= + ⋅⎢ ⎥⎢ ⎥+ −⎣ ⎦

MultiMulti--story SPSWstory SPSW

( )

1

1

2

11 tan2 1 1ibalance i

i

Lh

βκ αβ

−

−⎡ ⎤

= + ⋅ ⋅⎢ ⎥⎢ ⎥+ −⎣ ⎦

results in { {

strength demandii DF F=

=>

Design lateral force on SPSW

Modified lateral force to size infill panels

κnFDn

κiFDi

κi+1FDi+1

κi-1FDi-1

Fn

Fi+1

Fi

Fi-1

Lateral force applied to develop uniform yielding mechanism

FDn

FDi+1

FDi

FDi-1

hi-1

hi

hi+1

hn

LForce Used to Size Infill PanelsForce Used to Size Infill Panels

AISC

Proposed

where

( )

1

1

2

11 tan2 1 1

i ii

Lh

βκ αβ

−

−⎡ ⎤

= + ⋅ ⋅⎢ ⎥⎢ ⎥+ −⎣ ⎦

i j

n

p Dj i

V F=

= ∑

i j

n

p j Dj i

V Fκ=

= ∑

FDn

FDi+1

FDi

FDi-1

SPSW

hi-1

hi

hi+1

hn

17

Four eight-story SPSWs using different design assumptions to size the infill panels. (per AISC, Proposed, 75% and 40% respectively). Aspect ratio (L/h) is 1.8 in this study.

Case StudyCase Study

0.00 0.50 1.00 1.50 2.00 2.50 3.00Period (Sec)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

PSa

(g)

Location: Northridge (Zip: 91326)

Site class: B

2.138SS g= 1 0.744S g=Per USGS

Determined from deterministic limit earthquake on the known active faults around Northridge. (Equivalent to 2% probability of exceedance in 50 years)

Case StudyCase StudySummary of designed infill panels

Modified Story Shear (kip) Infill panel thickness (in) Story Level

Elevation (ft)

Lateral Force(kip) AISC proposed 75% 40% AISC proposed 75% 40%

8 80 127.1 127.1 113.0 95.3 50.8 0.033 0.029 0.025 0.013 7 70 137.9 264.9 233.6 198.7 106.0 0.069 0.060 0.051 0.027 6 60 117.9 382.8 335.5 287.1 153.1 0.099 0.087 0.074 0.040 5 50 97.9 480.7 422.9 360.5 192.3 0.124 0.109 0.093 0.050 4 40 78.0 558.7 492.0 419.0 223.5 0.144 0.127 0.108 0.058 3 30 58.2 616.9 542.8 462.7 246.8 0.160 0.140 0.120 0.064 2 20 38.5 655.5 575.8 491.6 262.2 0.170 0.149 0.127 0.068 1 10 19.0 674.5 590.1 505.9 269.8 0.174 0.153 0.131 0.070

Case StudyCase Study

0

10000

20000

30000

40000

50000

AISC PROPOSED 75% 40%

Wei

ght (

lb)

Panel HBE VBE Total

Note: HBEs in the weak-infill SPSW (40%) are sized using method (II)

Case StudyCase Study

Nonlinear time history analysis to assess performance of SPSWs using different design assumptions.Verified dual strip model (Qu and Bruneau, 2007)Target acceleration spectra compatible time histories (Papageorgiou, 2004).

0.00 0.50 1.00 1.50 2.00 2.50 3.00Period (Sec)

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

PSa

(g)

Realization-1Realization-2Realization-3Target design spectrum

0 2 4 6 8 10 12 14 16 18 20Time (Sec)

-0.8

-0.4

0

0.4

0.8

Acc

eler

atio

n (g

)

-0.8

-0.4

0

0.4

0.8

Acc

eler

atio

n (g

)

-0.8

-0.4

0

0.4

0.8

Acc

eler

atio

n (g

)

Realization-1

Realization-2

Realization-3

Case StudyCase Study

0 1 2 3 4 5Story Drift (%)

1

2

3

4

5

6

7

8

Stor

y Le

vel

8-Story SPSW Nolinear Time History Analysis

(Case: EQ2)

AISCPROPOSED75%40%

Preliminary ResultsPreliminary Results

Note: HBEs in the weak-infill SPSW (40%) are sized using method (II)

18

Things to be consideredThings to be considered

Ductile hysteretic loops Pinched hysteretic loops

“…Structural systems with larger energy dissipation capacity have larger Rd values, and hence are assigned higher R values, resulting in design for lower forces, than systems with relatively limited energy dissipation capacity… ” (from Page.37, FEMA 450 Commentary)

Blast Resistance of SPSWBlast Resistance of SPSW

Courtesy of John Pao, BPA Group, Bellevue, WA

Blast Resistance of SPSWBlast Resistance of SPSW Blast Resistance of SPSWBlast Resistance of SPSW

Blast Resistance of SPSWBlast Resistance of SPSW ConclusionsConclusionsRecently developed options for seismic design and retrofit illustrated (BRB with Fuse, TEBF, Rocking, SPSW)Instances for which replacement of sacrificial structural members (considered to be structural fuses dissipating hysteric energy) was accomplished, in some cases repeatedly. On-going research is expanding range of applicability

Reducing demands on SPSW boundary elementsMulti-hazard applications

Article/Clauses for the design of some of these systems are being considered by:

CSA-S16 committee for 2009 Edition of S16AISC TC9 Subcommittee for the 2010 AISC Seismic Provisions

19

Thank you!Thank you!

Questions?Questions?