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3rd Annual EHKS Retreat March 10, 2007 Allerton Park
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Transcript of 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
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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
3rd Annual EHKS Retreat3rd Annual EHKS RetreatMarch 10, 2007March 10, 2007
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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
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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
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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
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• 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
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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
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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
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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
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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
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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
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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
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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
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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
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Front View Side View
UIUC Half Scale TestsUIUC Half Scale Tests
3rd Annual EHKS Retreat3rd Annual EHKS RetreatMarch 10, 2007March 10, 2007
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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
Quasi-Quasi-StaticStatic33
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)
Steel Slit 3Steel Slit 3(82.6 kips)(82.6 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)
Steel Slit 2Steel Slit 2(123.9 kips)(123.9 kips)
1 1 weekweek
Quasi-Quasi-StaticStatic44
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)
Steel Slit 4Steel Slit 4(139.1 kips)(139.1 kips)
4 4 weeksweeks
Quasi-Quasi-StaticStatic33
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)
Steel Slit 5Steel Slit 5(92.7 kips)(92.7 kips)
1 1 weekweek
Quasi-Quasi-StaticStatic33
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
Quasi-Quasi-StaticStatic33
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)
Steel Slit 6Steel Slit 6(92.7 kips)(92.7 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.
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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
FreeFree Constrain to Constrain to be 0be 0
θ - torsionθ - torsion FreeFree Constrain to Constrain to be 0be 0
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
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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
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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
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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