seismic isolation of bridges and mission-critical...
TRANSCRIPT
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MULTIDISCIPLINARY CENTER FOR EARTHQUAKE ENGINEERING RESEARCH
Seismic Isolation of Bridges and Mission-Critical Infrastructure
Professor Andrew Whittaker, S.E.Professor Michael Constantinou
Department of Civil, Structural and Environmental EngineeringUniversity at Buffalo
University at Buffalo, State University of New York
Overview of presentation
• Seismic protective systems• Basic principles of operation• Hardware• Codes and guidance • Full-scale testing• Applications
– Bridges– Infrastructure
• Protective systems research at UB
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University at Buffalo, State University of New York
Seismic protective systems
MetallicFrictionViscoelasticViscous
Hybrid Systems
Seismic Isolation
Passive Damping
Semi-Activeand ActiveDamping
Smart Materials
Elastomeric Lead-rubberSliding (FP)
Variable Stiffnessand Damping
Mass Damper
ER FluidMR FluidSMA
University at Buffalo, State University of New York
Principles of seismic isolation
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University at Buffalo, State University of New York
Seismic isolation hardware
University at Buffalo, State University of New York
Elastomeric bearings
• Production– Compression mold
Seismic bearings– 1.5 m diameter
– Injection mold• Used for small bearings
• Vulcanization – Pressure – Temperature profile– Effect of variations in
profile
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University at Buffalo, State University of New York
Elastomeric bearings
• Low-damping natural rubber– Shear modulus in psi
75 min, 95 ave, 125 max
– Damping in the range of 2% to 6%– Temperature dependence
• High-damping rubber– Shear modulus in psi
55 min, 200 max
– Damping in the range of 7% to 14%– Properties depend on scragging, recovery,
aging, velocity, load-history, axial pressure
University at Buffalo, State University of New York
High-damping rubber bearings
-12
-8
-4
0
4
8
12
-300 -200 -100 0 100 200 300
Shear strain (%)
Shea
r for
ce (k
ips)
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University at Buffalo, State University of New York
Lead-rubber bearings
University at Buffalo, State University of New York
Lead-rubber bearings
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University at Buffalo, State University of New York
Friction Pendulum™ bearing
University at Buffalo, State University of New York
Friction Pendulum™ bearing
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University at Buffalo, State University of New York
Friction Pendulum™ bearing
University at Buffalo, State University of New York
Eradiquake™ bearing
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University at Buffalo, State University of New York
Fluid viscous dampers
University at Buffalo, State University of New York
Nonlinear VD, ± 175 mm, 1 m/sec, 665 kN
Fluid viscous dampers
-200
-150
-100
-50
0
50
100
150
200
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
Displacement (in)
Forc
e (k
ips)
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University at Buffalo, State University of New York
• Mandatory for – Bridges (AASHTO)– Buildings (NEHRP)– Nuclear (ASCE-4-98)
• Protocols– Prototype
Travel, braking, thermalSeismic
– ProductionQuality control
• Velocity effects– Static testing– Dynamic testing
Testing of seismic isolators and dampers
University at Buffalo, State University of New York
Bridge applications
EEL RIVER BRIDGE, CALIFORNIALEAD-RUBBER BEARINGS
KODIAK, ALASKAFP BEARINGS
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University at Buffalo, State University of New York
Codes and guidance
• 1999 AASHTO Guide Specification for Seismic Isolation Design– Analysis
Linear, nonlinear dynamic– Design– Testing
• 2003 NEHRP Recommended Provisions– Analysis, design, testing
• FHWA/Caltrans Technical Report on service and seismic design of protective hardware– Constantinou, Whittaker, et al.– 2007
• CERF/HITEC reports• Reports, manuals, books
University at Buffalo, State University of New York
Bridge applications
BENICIA-MARTINEZ BRIDGESAN FRANCISCO BAY AREA
FP BEARINGS
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University at Buffalo, State University of New York
Infrastructure applications
LNG TANKS, REVITHOUSSA, GREECEFP BEARINGS
University at Buffalo, State University of New York
Infrastructure applications
LNG TANKS, INCHON, KOREAELASTOMERIC BEARINGS
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University at Buffalo, State University of New York
Applications: Sakhalin II gas platforms
University at Buffalo, State University of New York
Applications: Sakhalin II gas platforms
• Mission-critical application— Protection of USD $10+B
• Application of seismic protective technologies
• Seismic isolation bearings under extreme compressive loading― Gravity: 7,000 tons― DLE: 15,000 tons
• Artic temperatures (-60ºF)• Challenges
― Isolator sizing― Heat flux calculations― Simplified dynamic analysis― Testing
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University at Buffalo, State University of New York
Applications: Sakhalin II gas platforms
• Maintain average and edge pressure• Maintain thickness of liner• Scale overlay thickness• Bearing thicknesses to maintain thermodynamic conditions• Testing procedure to simulate temperature rise due to frictional
heating (related to liner wear)
0
100
200
300
400
0 10 20 30 40Time (sec)
Tem
pera
ture
rise
(o C
)
Bidirectional seismic motion with varying axial load
Unidirectional sinusoidal motion, 250 mm amplitude, 0.6 Hz, 7 cycles, 33.6 N/mm2 pressure
University at Buffalo, State University of New York
Applications: Sakhalin II gas platforms
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University at Buffalo, State University of New York
Protective systems research at UB
• Hardware development– Lead-rubber bearings– Double concave FP bearings– XY FP bearings
• Systems development– Bridges– Nuclear structures
University at Buffalo, State University of New York
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11
11
22
22
R2
R1
Pivot Point
22
d d
h2
h1
u=u2
u1u2
u=u1+u2=2d
Double concave FP bearing (Fenz)
• Variant on the FP bearing– Two sliding surfaces
• Radii: R1 and R2
• Friction: µ1 and µ2
– Large displacement capacity• Nearly double that of FP
bearing with same plan dimensions
• Analytical formulations• Component testing
– Local behavior• Earthquake simulator testing
– System behavior
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University at Buffalo, State University of New York
DC-FP bearing component tests
Equal Radii and Equal Friction Specimen
Total Displacement, u (mm)
-125 0 125
Late
ral F
orce
Ver
tical
For
ce
-0.2
0.0
0.2
ExperimentalAnalytical
Top Displacement, u1 (mm)
-125 0 125
Late
ral F
orce
Ver
tical
For
ce
-0.2
0.0
0.2
Bottom Displacement, u2 (mm)
-125 0 125
Late
ral F
orce
Ver
tical
For
ce
-0.2
0.0
0.2
R1+R2-h1-h2=880 mm
R2-h2=442 mm
R1-h1=438 mm
µ1=0.058
µ2=0.057
Unequal Radii and Unequal Friction Specimen
Total Displacement, u (mm)
-125 0 125
Late
ral F
orce
Ver
tical
For
ce
-0.15
0.00
0.15
ExperimentalAnalytical
Top Displacement, u1 (mm)
-125 0 125
Late
ral F
orce
Ver
tical
For
ce
-0.15
0.00
0.15
Bottom Displacement, u2 (mm)
-125 0 125
Late
ral F
orce
Ver
tical
For
ce-0.15
0.00
0.15
R1+R2-h1-h2=1168 mm
R2-h2=442 mm
R1-h1=726 mm
µ1=0.038
µ2=0.021
University at Buffalo, State University of New York
DC-FP bearing system tests
100% NR Sylmar 90o Longitudinal Excitation
Isolation System Displacement (mm)-125 -100 -75 -50 -25 0 25 50 75 100 125
Tota
l Bas
e S
hear
Tota
l Ver
tical
Loa
d
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
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University at Buffalo, State University of New York
XY-FP bearing (Marin)
• Variant on the FP bearing– Orthotropic bearing
• Radii: R1 and R2
• Friction: µ1 and µ2
– Independent sliding along each rail
– Resistance to tensile axial loads
• Analytical formulations• Component testing
– Local behavior• Earthquake simulator
testing– System behavior
University at Buffalo, State University of New York
Vertical stiffness of rubber bearings (Warn)
• Influence of lateral displacement on vertical stiffness
• Improved models of elastomeric bearings
• Analytical studies
– Two spring model
• Finite element studies
• Component testing
– Single bearing test machine
• Earthquake simulator testing
– UB NEES facility
P
FH
θs
δv
u
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University at Buffalo, State University of New York
Vertical stiffness of rubber bearings
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.250
0.2
0.4
0.6
0.8
1
1.2
u/R
Kv /
(EcA
/Tr )
Two-spring LDR 5, ρ=2.75 MPaLDR 5, ρ=5.2 MPa LDR 5, ρ=9 MPa
u =152 mm
University at Buffalo, State University of New York
Vertical stiffness of rubber bearings
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 2.250
0.2
0.4
0.6
0.8
1
1.2
u/R
Kv /
(EcA
/Tr )
Two-spring LDR 5, ρ=2.75 MPaLDR 5, ρ=5.2 MPa LDR 5, ρ=9 MPa
u =152 mm
(Ave. Crit.: 75%)S, Mises
+6.544e+00+3.845e+03+7.684e+03+1.152e+04+1.536e+04+1.920e+04+2.304e+04+2.688e+04+3.072e+04+3.455e+04+3.839e+04+4.223e+04+4.607e+04
Step: Step-1Increment 17: Step Time = 1.000Primary Var: S, MisesDeformed Var: U Deformation Scale Factor: +1.000e+00
Low damping rubber bearingODB: LDRM2N0H100VC05.odb ABAQUS/STANDARD Version 6.5-1 Wed Aug 17 08:13:11 EDT 2005
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University at Buffalo, State University of New York
Vertical stiffness of rubber bearings
• Simulator system studies– 2 NEES 6 DOF simulators
• Bridge model– Weight = 90,000 lbs– Span = 35 ft
• Two isolation systems– Lead-rubber– Low-damping rubber
• Earthquake simulation program– Triaxial inputs
• Study influence of vertical stiffness on rocking response
• Provide data to validate new mathematical models– OpenSees, Matlab, 3D-Basis
University at Buffalo, State University of New York
Heating of lead cores (Kalpakidis)
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University at Buffalo, State University of New York
Heating of lead cores
• Thermal analysis – Predict change in isolator
mechanical properties • Input energy• Lead core diameter• Bearing geometry
– Heat conduction through• Shim plates• End plates
• Analytical studies– Transient response– Steady state response
• Finite element studies
0
50
100
150
200
250
300
350
400
0 5 10 15 20 25 30r (cm)
Tem
pera
ture
(o C
)
University at Buffalo, State University of New York
Closing Remarks
• Seismic isolation– Relatively mature technology
Elastomeric and sliding isolators
– ApplicationsBridgesInfrastructure
– Opportunities for improvement in hardware and systems
– On-going research program at UB