tools for isolation and protective systems quake summit 2012 boston, massachusetts, july 12, 2012...
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Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
NEES TIPS/E-Defense Tests of a Full Scale Base-Isolated and Fixed-Base Building
Keri L. RyanAssistant Professor/ University of Nevada,
RenoNEES TIPS Principal Investigator
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Project Collaborators
• Prof. Keri Ryan (University of Nevada, Reno)
• Prof. Stephen Mahin (UC Berkeley)• Prof. Gilberto Mosqueda (U. Buffalo)• Prof. Manos Maragakis (University of
Nevada, Reno)• Prof. Kurt McMullin (San Jose State
University)• Prof. Troy Morgan (Tokyo Tech.)• Prof. Kazuhiko Kasai (Tokyo Tech.)• Prof. Arash Zaghi (U. Conn)
• Dr. Eiji Sato (NIED)• Dr. Tomohiro Sasaki (NIED)• Prof. Taichiro Okazaki (Hokkaido
University)• Prof. Masayoshi Nakashima (Kyoto
University)• Dr. Koichi Kajiwara (NIED)
Japan/NIED ResearchersUS/NEES Researchers
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Project Collaborators
• Earthquake Protection Systems• Dynamic Isolation Systems• Aseismic Design Company• Takenaka Corporation• USG Building Systems• Hilti Corporation• CEMCO Steel• Victaulic• Tolco
• Nhan Dao• Keisuke Sato• Camila Coria• Siavash Soroushian
StudentsIndustry Collaborators/Sponsors
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Shake table tests of 5-story steel moment frame building in 3 different configurations isolated with triple friction pendulum
bearings (TPB) Isolated with lead-rubber bearings and
cross linear bearings (LRB/CLB) “fixed-base” configuration
Evaluate response of the structure, nonstructural components, and contents for all configurations
Scope of Test Program
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Triple Pendulum (TPB) Test Objectives
Demonstrate seismic resiliency of the system in a very large event. Provide continued functionality and minimal disturbance to contents.
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Lead Rubber (LRB/CLB) Test Objectives
Evaluate performance of an elastomeric isolation system designed for a nuclear power plant in beyond design basis shaking Designed for “Vogtle”, a
representative central and eastern U.S. soil site
Performance Objectives for Bearings Sustain large displacement demands Retain axial load carrying capacity at these
large displacements
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Other Test Objectives
Extend resiliency to systems with challenging configurationso Lightweight structure (500 tons)o Demonstrate torsion reduction in
an asymmetric building
Roof Plan
Asymmetry of system enhancedwith asymmetric steel plates attached at roof for added mass. The roof was designed for the extra load, which could represent combined load of roof mounted equipment, roof penthouse, etc.
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Triple Pendulum (TPB) Isolators and Configuration
1.4 m (55 in)
.33 m(13 in)
9 isolators, one beneath each column
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Lead Rubber (LRB/CLB) Isolation System
Lead Rubber Bearings 70 cm (27.5 in) diameter 4 bearings -> TD = 2.8 sec Capacity of 50 tons at 60 cm
Cross Linear Sliders Flat slider with 0.25% cof Tension resistance Carries weight at large
displacements
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
5 cross linear bearings
4 lead rubber bearings
LRB/CLB System Configuration
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Characteristics of Each System
0.020W
0.080W
T1=1.84s
T2=5.57s
Teff=4.55s
0.214W
0.275W
0.053W
0.37W
T2=2.78s
Teff=2.55s
Yield Force = 0.08W T2 = 5.57 sec Disp. Capacity = 1.14 m (45 in)
Triple Pendulum LRB/CLB
Yield Force = 0.053W T2 = 2.78 sec
Disp. Capacity = 0.6 m (24 in)
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Innovation to Capture Forces in Isolators
Force-deformation of full scale isolators in a system test captured for the first time!
9 custom-made steel plate load cell assemblies, each using 7 or 9 distributed load cells to absorb axial forces from overturning
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Superstructure Modeling
3D frame model built in OpenSees Beams and slabs modeled as
composite sections Rigid diaphragm constraint Mass lumped to every node of the
model Beams divided into several
elements for distributing mass to model
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Modeling of Columns
Displacement-based distributed plasticity elements with fiber sections; 3 elements per column
Giuffre Menegotto Pinto steel material
-0.02 -0.01 0 0.01 0.02-400
-200
0
200
400
Strain,
Str
ess,
(M
Pa)
y
y
-0.02 -0.01 0 0.01 0.02-400
-200
0
200
400
Strain,
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Modeling of Beams Displacement-based distributed plasticity element with
resultant sections; 8 elements per beam Resultant section behavior developed from section analysis of
composite section Effective slab width = L/8 in each direction
-0.02 -0.01 0 0.01 0.02-2
-1.5
-1
-0.5
0
0.5
1
1.5
Curvature, (rad/m)
Mom
ent,
M (M
Nm
)
Fiber SectionResultant Section
Concrete
Steel
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Beam to Column Connections
Krawinkler panel zone model Assemblage of rigid links and rotational springs
Panel web
BeamColumn
Beam
Column
Rigid element
Hinge
Spring representing
column flanges
Spring representing panel web
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Damping in Superstructure
Rayleigh Damping used for both isolated and fixed-base Damping anchored at 2.2% at 0.7 sec and 0.15 sec for fixed-base Damping anchored at 1.5% at 2.0 sec and 2.5% at 0.15 sec for
isolated
0 2 4 6 8 100
2
4
6
8
10
Frequency, f (Hz)
Dam
ping
rat
io,
(%)
Fixed-base modelIsolated-base modelFixed-base test
Supplemental damper was added from base to roof to increase damping across first structural mode
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Modeling of TPB
Model assembled elastic-plastic springs and gap elements in series to represent stages of sliding
Bi-directional coupling (circular gap element) Horizontal-vertical coupling
Element 1
Element 4
Element 2
Element 5
Element 3
Element 6-0.5 0 0.5
-60
-40
-20
0
20
40
60
Displacement, uX (m)
For
ce,
Fx (
kN)
CoupledUncoupled
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Dynamic Variation of Friction Coefficient
Bearing formulation incorporates variation of friction coefficient with axial force and velocity
μ average = 9.8%
0 2 4 6 8 10 12
x 105
0
0.05
0.1
0.15
Vertical force, W (N)
Fric
tion
coef
ficie
nt,
min
=8.701 W -0.34
max
=17.239 W -0.38
Slow frictionFast frictionFitted curves
0 0.1 0.2 0.3 0.40
0.05
0.1
0.15
Velocity, v (m/s)
Fric
tion
coef
ficie
nt,
= 0.142 - 0.023 e-22.92 v
= 0.090 - 0.011 e-16.69 v
W=1019 kN
W=308 kN
Velocity EffectAxial Force Effect
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Calibrated Model for Sine Wave Test
Generalized friction model incorporating axial force and velocity effects more closely matches the test data than a constant friction model
Constant Friction ModelGeneralized Friction Model
-0.5 0 0.5-0.2
-0.1
0
0.1
0.2
Displacement, u (m)
Nor
mal
ized
forc
e, f
TestGen.
0
-0.5 0 0.5-0.2
-0.1
0
0.1
0.2
Displacement, u (m)
Nor
mal
ized
forc
e, f
TestConst.
0
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Model Verification for 100% Tabas
Peak displacement: Test = 0.691 m, Model = 0.677 m Generalized friction model predicted the peak
displacement better than constant friction models.
-75 -50 -25 0 25 50 75-50
0
50
Disp. X, uX (cm)
Dis
p. Y
, u Y
(cm
)
TestAnalysis
-75 -50 -25 0 25 50 75-100
-50
0
50
100
150
200
Disp. X, uX (cm)
For
ce X
, F
X (
kN)
Displacement Trace Bearing Hysteresis
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Modeling of LRB/CLB
Bilinear force-deformation in horizontal direction with bidirectional coupling
Bilinear elastic response in vertical direction with different stiffnesses in tension and compression
Horizontal and vertical behavior were uncoupled
Displacement
Force
K1
KdFy
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Characterization of LRB
Because of amplitude dependence, bearing parameters were characterized independently for every test
-50 0 50
-100
-50
0
50
100
E-Bearing
Fo
rce
X (
kN)
-50 0 50
-100
-50
0
50
100
S -Bearing
-50 0 50
-100
-50
0
50
100
N-Bearing
Fo
rce
X (
kN)
Disp. X (cm)-50 0 50
-100
-50
0
50
100
W-Bearing
Disp. X (cm)
Analys isTes t
-500 0 500-400
-200
0
200
400E-Bearing
Fo
rce
X (
kN)
-500 0 500-400
-200
0
200
400S -Bearing
-500 0 500-400
-200
0
200
400N-Bearing
Fo
rce
X (
kN)
Disp. X (cm)-500 0 500
-400
-200
0
200
400W-Bearing
Disp. X (cm)
Analys isTes t
Westmorland 80%
Diablo Canyon 95%
Disp. (mm)
Disp. (mm)
Forc
e (k
N)
Forc
e (k
N)
Peak Disp = 8.8 cmQD = 33.4 kNkD = 11.0 kN/cm
Peak Disp = 54.7 cmQD = 70.3 kNkD = 6.2 kN/cm
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Model Verification for 95% Diablo Canyon
Even rigorous characterization led to mixed results for displacement prediction.
Model optimized for peak cycle gave poor results for smaller cycles.
Trial and error adjustments were made.
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Floor Acceleration Response in LRB/CLB System, XY vs 3D Motion (Vert. PGA =
0.7g)
Floor Spectra for Diablo Canyon 95%, x-direction
Period (sec)
Acce
lera
tion
(g)
Floor 1 Floor 2 Floor 3
Floor 4 Floor 5 Floor 6
Mode 1
Isolation ModeT = 2.72 sec
Analysis of Floor Spectra, LRB System XY Input
Mode 5
1st Structural ModeT = 0.36 sec
Floor Spectra for Diablo Canyon 95%, x-direction
Period (sec)
Acce
lera
tion
(g)
Floor 1 Floor 2 Floor 3
Floor 4 Floor 5 Floor 6
Analysis of Floor Spectra, LRB System XY Input
Mode 8
2nd Structural ModeT = 0.17 sec
Floor Spectra XY vs. 3D Input, LRB SystemX-direction
Y-direction
Acce
lera
tion
(g)
Acce
lera
tion
(g)
F1 F2 F3
F4 F5 F6
F1 F2 F3
F4 F5 F6
Additional peaks in y-direction for 3D input
Floor Spectra for Diablo Canyon 80%, y-direction
Period (sec)
Acce
lera
tion
(g)
Floor 1 Floor 2 Floor 3
Floor 4 Floor 5 Floor 6
Analysis of Floor Spectra, LRB System 3D Input
3rd Structural ModeY-directionT = 0.1 sec
3rd Structural ModeX-directionT = 0.1 sec
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Floor Acceleration Response in TPB System, XY vs. 3D Motion
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Floor Acceleration Response in TPB System, 3D Takatori (Vert. PGA = 0.28g)
Mode 8
2nd Structural ModeT = 0.17 sec
The acceleration profile in X-dir follows the 2nd structural mode.
Floor Spectra for Takatori 100%, x-direction
Analysis of Floor Spectra, TPB System 3D Input
Mode 8
2nd Structural ModeT = 0.17 sec
Tools for Isolation and Protective Systems
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Base Shear in TPB System, 3D Takatori (Vert. PGA = 0.28g)
Oscillation at 7 Hz (0.14 sec) due to vertical acceleration is transmitted to the base shear, and amplifies the second structural mode.
Tools for Isolation and Protective Systems
2012 Structures Congress
Chicago, Illinois, March 29-31, 2012
Concluding Remarks
• Rigorous analysis clarified interesting (unexpected) findings regarding the behavior of the isolated buildings.
• A 3D TPB model that includes dynamic variation of friction coefficient with axial force and velocity can predict the displacement demand very well.
• The damping in the steel structure (remaining linear) was very low; a damping ratio between 1-2% in all modes is recommended. Participation of higher modes was greater than expected.
• Under vertical ground input, horizontal floor accelerations were amplified due to modal coupling in the structure and axial-shear coupling in the TPB bearings. Time history analysis of the system with 3D input is essential to understand and predict these effects, which were significant in the tests.
Tools for Isolation and Protective Systems
2012 Structures Congress
Chicago, Illinois, March 29-31, 2012
Thanks to the many sponsors!• National Science Foundation NEES Program
– (Grant No. CMMI-1113275 and CMMI-0721399)
• Nuclear Regulatory Commission• Earthquake Protection Systems• Dynamic Isolation Systems, Aseismic Devices Company, Sumiken
Kansai, THK• Takenaka Corporation• USG Building Systems, CEMCO Steel, Victaulic, Tolco, Hilti• Japan Society for the Promotion of Science (JSPS)