3rd Annual EHKS Retreat March 10, 2007 Allerton Park

3rd Annual EHKS Retreat3rd Annual EHKS RetreatMarch 10, 2007March 10, 2007Allerton ParkAllerton Park

Controlled Rocking Steel Frames Controlled Rocking Steel Frames with Replaceable with Replaceable

Energy-Dissipating FusesEnergy-Dissipating Fuses

Matt Eatherton, MS SEUniversity of Illinois at Urbana-Champaign

3rd Annual EHKS Retreat3rd Annual EHKS RetreatMarch 10, 2007March 10, 2007

Allerton ParkAllerton ParkMy BackgroundMy Background

• Born in Kansas City, 1975Born in Kansas City, 1975• BS in CE - University of Missouri at Columbia, 1997BS in CE - University of Missouri at Columbia, 1997• MS in CE - University of Missouri at Columbia, 1999MS in CE - University of Missouri at Columbia, 1999

– Master’s research involved instrumenting and monitoring four Master’s research involved instrumenting and monitoring four prestressed bridge girders with over 150 gages during construction and prestressed bridge girders with over 150 gages during construction and for one year in service.for one year in service.

• 2 years structural design experience in Kansas City2 years structural design experience in Kansas City• 5 years structural design experience in San Francisco5 years structural design experience in San Francisco• Volunteer Structural Engineering ActivitiesVolunteer Structural Engineering Activities

– Build Change – improving seismic resistance of housing in developing Build Change – improving seismic resistance of housing in developing countriescountries

– SEAONC subcommittee – investigated diaphragm forcesSEAONC subcommittee – investigated diaphragm forces– Steel Plate Shear Walls – several projects, conference articles, design Steel Plate Shear Walls – several projects, conference articles, design

examples, and other involvementexamples, and other involvement

• Began PhD program at UIUC in fall 2006 with the goal of getting an Began PhD program at UIUC in fall 2006 with the goal of getting an academic position afterwardacademic position afterward


Allerton ParkAllerton ParkOrganizationOrganization

1.1. IntroductionIntroduction

2.2. Controlled Rocking SystemControlled Rocking System

3.3. Parametric Study & Prototype BuildingParametric Study & Prototype Building

4.4. UIUC Half-Scale Test ProgramUIUC Half-Scale Test Program

5.5. ConclusionsConclusions


Allerton ParkAllerton Park

Two story steel-framed office building in Santa Clarita suffered residual drift in the first story due to the Northridge Earthquake.

From EERI Earthquake Recon. Report, Jan. 1996 & May 1990

Building with a Red Tag restricting access after the Northridge Earthquake

Industrial Structure that experienced brace

buckling and residual drift during Loma Prieta

Expected Building PerformanceExpected Building Performance



Component 1 – Stiff braced frame, designed to remain essentially elastic - not tied down to the foundation.

Component 2 – Post-tensioning strands bring frame back down during rocking

Component 3 – Replaceable energy dissipating fuses take majority of damage

Bumper or Trough

Controlled Rocking SystemControlled Rocking System



• Corner of frame is allowed to uplift.

• Fuses absorb seismic energy

• Post-tensioning brings the structure back to center.

Result is a building where the structural damage is concentrated in replaceable fuses and virtually no residual drift!

Rocked ConfigurationRocked Configuration



BAVA

FM pPTresist

22

FPT

Vp/3

Vp/3

Vp/3

F1

F2

F3FPT

“A” “B” “A”

“H1”

“H2”

“H3”

ovtresist MM

FPT = Initial post-tension force

Vp = Fuse yield strength in shear

Overturning moment =

Resistance comes from Post-Tensioning and Fuses:

In an LRFD context use a resistance factor to design:

iiovt HFM

Can also include gravity loads

Design Equations - Overturning Design Equations - Overturning ResistanceResistance



BAVA

F pPT

22

In the rocked configuration, the fuses resist self-centering. The restoring moment due to P/T must overcome the restoring resistance:

FPT

Vp/3

Vp/3

Vp/3

FPT

“A” “B” “A”

Other sources of resistance not considered in this equation include:

• Stiffness of gravity system

• Stiffness of interior partitions that have undergone inelastic damage

• P-delta effect

Can also include effect of gravity load in restoring force.

Design Equations - Self-Centering Design Equations - Self-Centering MechanismMechanism



effeff B

BARDR

B

)( BARDR Fuse Shear Strain, =

Shear strain in the fuses is amplified compared to the roof drift ratio (RDR).

Using small angle assumption:

Example:

068.0'33.5

'6'1202.0

Fuse Shear Strain DemandFuse Shear Strain Demand



0 0.005 0.01 0.015 0.020

50

100

150

Roof Drift Ratio (mm/mm)

Ba

se S

he

ar

(kN

)

4

1

3

2 5

6

FLAG SHAPED HYSTERESIS

1. Begin Loading

2. Frame Uplifts

3. Fuses Yield

4. Load reversal. If pushed far enough P/T would yield

5. Zero force in fuses

6. Fuses yield in other direction

7. Frame sets back down and forces in the frame relax.

8. Elastic strain energy remains in frame and fuses

7

8

Controlled Rocking – Hysteretic Controlled Rocking – Hysteretic ResponseResponse



1. Global Overturning (FPT > Vp)

2. Initial P/T stress: Stressing the P/T strands 0.4 Fu may require special procedures to anchor post-tensioning (post-blocking).

3. P/T strain capacity: If performance criteria includes not replacing P/T after a severe earthquake then ensure adequate strain capacity.

Fuse Strength

VP

Initial Post-

Tensioning, FPT

To Prevent Dual

Frame Rocking:

FPT > VP

Preventing Global Overturning

Other Design ConsiderationsOther Design Considerations



Use prototype structure to apply controlled rocking to a realistic structure

Based on SAC Building configuration

Tests and analysis simulate the controlled rocking frames in this structure.

Prototype StructurePrototype Structure



12'-0" 6'-0" 12'-0"

13'-0"

13'-0"

13'-0"

W12X26

W12 X30

W12X26

W12 X30

W12

X12

0

W12

X17

0

W12

X17

0

W12

X12

0

W12 X30

W12X26

W12 X30

W12X26

W12

X10

6 W12X

96

W12X

53

W12

X87

W12

X96

W12X

53

W12X

106W12

X96

W12

X53

W12X

87

W12X

96

W12

X53

Prototype – Controlled Rocking Prototype – Controlled Rocking FramesFrames



Goals:

1. To test and improve details – post-tensioning and base connections are not typical to steel structures.

2. Study the forces realized in the fuses and distribution of force between fuses. Geometric nonlinearity and indeterminacy creates complexity.

3. Examine effect of out-of-plane motion while rocking.

4. Determine whether typical P/T strands and anchorage can be stressed to yield without fracturing or slipping.

5. Establish whether there is inelasticity or relaxation in the P/T that would require replacement or re-stressing.

6. Investigate whether inelasticity occurs in the frame.

VERIFY THE PERFORMANCE OF THE SYSTEM FOR IMPLEMENTATION IN PRACTICE

UIUC Half Scale TestsUIUC Half Scale Tests



Front View Side View

UIUC Half Scale TestsUIUC Half Scale Tests


Allerton ParkAllerton ParkTest MatrixTest Matrix

Test Test IDID

Dim Dim “B” “B” 11

A/B A/B RatioRatio

OT OT RatioRatio

Initial P/T Initial P/T StressStress22 and and

ForceForce

Fuse Type Fuse Type and Fuse and Fuse StrengthStrength

Time Time Req’dReq’d

Testing Testing ProtocolProtocol

Reason for TestReason for Test

A1A1 3.09’3.09’ 1.751.75 1.01.0(R=8)(R=8)

0.314 Fu0.314 Fu(103.9 (103.9 kips)kips)

Steel Slit 1Steel Slit 1(82.6 kips)(82.6 kips)

4 4 weeksweeks

Quasi-Quasi-StaticStatic33

This configuration should produce the least amount of demands on This configuration should produce the least amount of demands on the fuses. If there are problems with the fuses, we may be able to the fuses. If there are problems with the fuses, we may be able to reconfigure.reconfigure.

A2A2 3.09’3.09’ 1.751.75 1.01.0(R=8)(R=8)

0.314 Fu0.314 Fu(103.9 (103.9 kips)kips)

ECC 1 ECC 1 (82.6 kips)(82.6 kips)

1 1 weekweek


If the system works in the first test, try an ECC fuse in this best-If the system works in the first test, try an ECC fuse in this best-case configuration.case configuration.

A3A3 3.09’3.09’ 1.751.75 1.01.0(R=8)(R=8)

0.314 Fu0.314 Fu(103.9 (103.9 kips)kips)


2 2 weekweek

Hybrid Hybrid Simu-Simu-lationlation44

Now that we know how well this configuration responds, conduct a Now that we know how well this configuration responds, conduct a hybrid simulation to find out how the system will perform in a real hybrid simulation to find out how the system will perform in a real building. One of the main objectives is to examine effect of out-of-building. One of the main objectives is to examine effect of out-of-plane rotation.plane rotation.

A4A4 3.09’3.09’ 1.751.75 1.51.5(R=5.3)(R=5.3)

0.471 Fu0.471 Fu(155.8 (155.8 kips)kips)


1 1 weekweek


Increase the OT to 1.5. The higher OT would result in lower Increase the OT to 1.5. The higher OT would result in lower ductility demands, so if it works, this would be the configuration ductility demands, so if it works, this would be the configuration proposed for better performance in a PBD. This configuration will proposed for better performance in a PBD. This configuration will also cause P/T yielding before the fuses are completely destroyed.also cause P/T yielding before the fuses are completely destroyed.

B1B1 2.16’2.16’ 2.52.5 1.51.5(R=5.3)(R=5.3)

0.471 Fu0.471 Fu(155.8 (155.8 kips)kips)


4 4 weeksweeks


Now that we have an idea how well the system works, push the A/B Now that we have an idea how well the system works, push the A/B to 2.5, but with an OT of 1.5. This configuration still produced to 2.5, but with an OT of 1.5. This configuration still produced reasonable fuse shear strain demands in the parametric study.reasonable fuse shear strain demands in the parametric study.

B2B2 2.16’2.16’ 2.52.5 1.01.0(R=8)(R=8)

0.314 Fu0.314 Fu(103.9 (103.9 kips)kips)


1 1 weekweek


Drop the OT back to 1.0. This configuration pushes the envelope Drop the OT back to 1.0. This configuration pushes the envelope with regards to fuse shear strain demand predicted by the with regards to fuse shear strain demand predicted by the parametric study.parametric study.

B3B3 2.16’2.16’ 2.52.5 1.01.0(R=8)(R=8)

0.314 Fu0.314 Fu(103.9 (103.9 kips)kips)

ECC 2ECC 2(92.7 kips)(92.7 kips)

1 1 weeksweeks


If the previous test with A/B = 2.5 and OT = 1.0 works, try an ECC If the previous test with A/B = 2.5 and OT = 1.0 works, try an ECC fuse. fuse. *We will cast another set of ECC fuses based on OT=1.5 and A/B = *We will cast another set of ECC fuses based on OT=1.5 and A/B = 2.5, in case system isn’t performing as well as expected. 2.5, in case system isn’t performing as well as expected.

B4B4 2.16’2.16’ 2.52.5 1.01.0(R=8)(R=8)

0.314 Fu0.314 Fu(103.9 (103.9 kips)kips)


2 2 weekweek

Hybrid Hybrid Simu-Simu-lationlation44

For the finale, try a hybrid simulation at A/B = 2.5. Along with For the finale, try a hybrid simulation at A/B = 2.5. Along with other hybrid simulation, this will tell us how well the system might other hybrid simulation, this will tell us how well the system might perform in a real building.perform in a real building.



Degree of FreedomDegree of Freedom Left LBCBLeft LBCB Right LBCBRight LBCB

ForceForce MovementMovement ForceForce MovementMovement

U - horizontalU - horizontal FreeFree USE THIS USE THIS AS AS

CONTROLCONTROL

Constrain to Match Constrain to Match Force of left LBCBForce of left LBCB

FreeFree

U - verticalU - vertical Gravity Load Gravity Load SpecifiedSpecified

FreeFree Gravity Load Gravity Load SpecifiedSpecified

FreeFree

U - out-of-planeU - out-of-plane FreeFree Constrain to Constrain to be 0be 0

FreeFree Constrain to Constrain to be 0be 0

θ - in-planeθ - in-plane As necessary to As necessary to simulate applying simulate applying

gravity load to gravity load to exterior columnsexterior columns

FreeFree As necessary to As necessary to simulate applying simulate applying

gravity load to gravity load to exterior columnsexterior columns

FreeFree

θ - out-of-planeθ - out-of-plane FreeFree Constrain to Constrain to be 0be 0


θ - torsionθ - torsion FreeFree Constrain to Constrain to be 0be 0


The horizontal movement of the Left LBCB would be used to control the test. The Right LBCB will match the horizontal force in the left LBCB. This will apply the same amount of load to both frames, but allow differential rocking between the frames.

Mixed Mode ControlMixed Mode Control



1. Seismic loads prescribed in current building codes assume considerable inelasticity in the structure during a severe earthquake. This can result in structural damage and residual drift that cannot be economically repaired.

2. To provide a building that is relatively easy to repair after an earthquake, two attractive performance criteria are:a) Eliminate residual drift.b) Concentrate bulk of structural damage in replaceable fuses.

3. The controlled rocking system satisfies these performance goals.

4. The controlled rocking system consists of three major components:a) Stiff steel braced frame designed to remain essentially elastic, but

not tied down to the foundation.b) Post-tensioning that provides self-centering capability.c) Highly ductile energy dissipating fuses.

5. A multi-institution, international research project is underway to examine, improve, and validate the performance of this innovative system.

SummarySummary



6. A parametric study was conducted to optimize A/B ratio, OT ratio, and SC ratio.

7. Some considerations in the design of the controlled rocking system include:a) Proportioning fuses and P/T to resist overturning, but still self-

center.b) Insuring enough P/T strain capacity.c) Using fuses with enough shear strain capacity based on frame

geometry (fuse shear strain is amplified compared to roof drift ratio).d) Preclude global overturning.

8. Half-scale tests will be conducted later this year at the UIUC MUST-SIM Facility to improve details and validate the performance of the controlled rocking system for implementation in practice.

9. Hybrid simulation tests will further validate the system performance and demonstrate the self-centering and repairability of the controlled rocking system when subjected to a realistic ground motion.

SummarySummary



PI Greg Deierlein – Project Manager, Stanford University

Co-PI Sarah Billington – ECC & HPFRCC Fuses, Stanford Unviersity

Co-PI Jerome Hajjar – Simulation and Half-Scale Tests, University of Illinois

Helmut Krawinkler, Stanford University

Mitsumasa Midorikawa – E-Defense, Building Research institute in Japan

David Mar - Industry Collaborator, Tipping and Mar Engineers

Current Graduate Students: Xiang Ma (Stanford), Matt Eatherton (UIUC)

Past Graduate Students: Paul Cordova (Post-Doc at Stanford), Eric Borchers (Stanford), Kerry Hall (UIUC),

Project is funded by a grant from NSF - NEESR-SG

E-DEFENSE

JAPAN

Research TeamResearch Team

3rd Annual EHKS Retreat March 10, 2007 Allerton Park

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