Tools for Isolation and Protective Systems
NEES TIPS/E-Defense Tests of a Full Scale BaseIsolated and Fixed-Base Building
Keri L. Ryan
Assistant Professor/ University of Nevada, Reno
NEES TIPS Principal Investigator
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Project Collaborators
US/NEES Researchers
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Japan/NIED Researchers
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)
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Dr. Eiji Sato (NIED)
Dr. Tomohiro Sasaki (NIED)
Prof. Taichiro Okazaki (Hokkaido
University)
Prof. Masayoshi Nakashima (Kyoto
University)
Dr. Koichi Kajiwara (NIED)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Project Collaborators
Industry Collaborators/Sponsors
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Earthquake Protection Systems
Dynamic Isolation Systems
Aseismic Design Company
Takenaka Corporation
USG Building Systems
Hilti Corporation
CEMCO Steel
Victaulic
Tolco
Students
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Nhan Dao
Keisuke Sato
Camila Coria
Siavash Soroushian
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Scope of Test Program
 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
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Triple Pendulum (TPB) Test Objectives
 Demonstrate seismic resiliency of
the system in a very large event.
Provide continued functionality and
minimal disturbance to contents.
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
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
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Other Test Objectives
 Extend resiliency to systems
with challenging configurations
o Lightweight structure (500 tons)
o Demonstrate torsion reduction in
an asymmetric building
Asymmetry of system enhanced
with 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.
Roof Plan
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Triple Pendulum (TPB) Isolators and
Configuration
9 isolators, one beneath each column
1.4 m (55 in)
.33 m
(13 in)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Lead Rubber (LRB/CLB) Isolation System
 Lead Rubber Bearings
 Cross Linear Sliders
 70 cm (27.5 in) diameter
 Flat slider with 0.25% cof
 4 bearings -> TD = 2.8 sec
 Tension resistance
 Capacity of 50 tons at 60 cm
 Carries weight at large
displacements
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
LRB/CLB System Configuration
5 cross linear
bearings
4 lead rubber
bearings
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Characteristics of Each System
Triple Pendulum
LRB/CLB
0.37W
T2=5.57s
T2=2.78s
0.275W
0.214W
0.080W
0.053W
0.020W
Teff=2.55s
T1=1.84s
Teff=4.55s
 Yield Force = 0.08W
 T2 = 5.57 sec
 Disp. Capacity = 1.14 m (45 in)
 Yield Force = 0.053W
 T2 = 2.78 sec
 Disp. Capacity = 0.6 m (24 in)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
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
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
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
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Modeling of Columns
 Displacement-based distributed plasticity elements with fiber
sections; 3 elements per column
 Giuffre Menegotto Pinto steel material
400
200
0
-200
y
-0.01
0
Strain, 
0.01
0.02
-400
-0.02
-0.01
0
Strain, 
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
0.01
0.02
Tools for Isolation and Protective Systems
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
1.5
Concrete
Steel
Moment, M (MNm)
1
0.5
0
-0.5
-1
Fiber Section
Resultant Section
-1.5
-2
-0.02
-0.01
0
0.01
Curvature,  (rad/m)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
0.02
Tools for Isolation and Protective Systems
Beam to Column Connections
 Krawinkler panel zone model
 Assemblage of rigid links and rotational springs
Panel web
Spring
representing
panel web
Rigid element
Hinge
Beam
Column
Beam
Column
Spring
representing
column flanges
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Damping in Superstructure
Damping ratio,  (%)
 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
10
Fixed-base model
 Supplemental damper was added
Isolated-base model
8
Fixed-base test
from base to roof to increase
6
damping across first structural
4
mode
2
0
0
2
4
6
Frequency, f (Hz)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
8
10
Tools for Isolation and Protective Systems
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 2
60
Element 3
Coupled
Uncoupled
Force, Fx (kN)
40
20
0
-20
-40
-60
Element 4
Element 5
Element 6
-0.5
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
0
Displacement, uX (m)
0.5
Tools for Isolation and Protective Systems
Dynamic Variation of Friction
Coefficient
 Bearing formulation incorporates variation of friction coefficient
with axial force and velocity
 μ average = 9.8%
Axial Force Effect
max=17.239 W
0.1
min=8.701 W -0.34
0.05
0
0
Slow friction
Fast friction
Fitted curves
2
4
6
8
Vertical force, W (N)
10
 = 0.142 - 0.023 e-22.92 v
-0.38
12
5
x 10
W=308 kN
0.15
Friction coefficient, 
Friction coefficient, 
0.15
Velocity Effect
W=1019 kN
0.1
0.05
0
0
 = 0.090 - 0.011 e-16.69 v
0.1
0.2
0.3
Velocity, v (m/s)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
0.4
Tools for Isolation and Protective Systems
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
Generalized Friction Model
0.2
Test
Gen. 0
Normalized force, f
Normalized force, f
0.2
0.1
0
Test
Const. 0
0.1
0
-0.1
-0.1
-0.2
-0.5
Constant Friction Model
0
Displacement, u (m)
0.5
-0.2
-0.5
0
Displacement, u (m)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
0.5
Tools for Isolation and Protective Systems
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.
Displacement Trace
Bearing Hysteresis
200
50
150
Force X, FX (kN)
Disp. Y, uY (cm)
Test
Analysis
100
0
50
0
-50
-50
-75
-50
-25
0
25
Disp. X, uX (cm)
50
75
-100
-75
-50
-25
0
25
Disp. X, uX (cm)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
50
75
Tools for Isolation and Protective Systems
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
Force
Kd
Fy
K1
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Displacement
Tools for Isolation and Protective Systems
Characterization of LRB
Westmorland 80%
100
50
0
0
-50
-50
Force X (kN)
-100
-100
-50
0
50
-50
N-Bearing
0
50
Peak Disp = 8.8 cm
QD = 33.4 kN
kD = 11.0 kN/cm
100
50
50
0
0
-50
-50
-100
0
0
-200
-200
Force X (kN)
200
0
500
-400
-500
N-Bearing
400
200
200
0
0
-200
-200
0
Disp. X (cm)
50
-50
Disp. (mm)
0
Disp. X (cm)
50
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
500
W-Bearing
400
-400
-500
0
500
-400
-500
Disp. (mm)
0
Disp. X (cm)
Peak Disp = 54.7 cm
QD = 70.3 kN
kD = 6.2 kN/cm
-100
0
Disp. X (cm)
200
W-Bearing
100
-50
S-Bearing
400
Analysis
Test
-400
-500
S-Bearing
50
Force (kN)
Force X (kN)
100
E-Bearing
400
Force X (kN)
E-Bearing
Analysis
Test
Diablo Canyon 95%
Force (kN)
 Because of amplitude dependence,
bearing parameters were characterized
independently for every test
500
Tools for Isolation and Protective Systems
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.
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Floor Acceleration Response in LRB/CLB
System, XY vs 3D Motion (Vert. PGA = 0.7g)
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Analysis of Floor Spectra, LRB System
XY Input
Mode 1
Floor Spectra for Diablo Canyon 95%, x-direction
Isolation Mode
T = 2.72 sec
Mode 5
1st Structural Mode
T = 0.36 sec
Acceleration (g)
Floor 1
Floor 4
Floor 2
Floor 5
Period (sec)
Floor 3
Floor 6
Analysis of Floor Spectra, LRB System
XY Input
Floor Spectra for Diablo Canyon 95%, x-direction
Floor 1
Floor 2
Floor 3
2nd Structural Mode
T = 0.17 sec
Acceleration (g)
Mode 8
Floor 4
Floor 5
Period (sec)
Floor 6
Floor Spectra XY vs. 3D Input, LRB System
Acceleration (g)
X-direction
F1
F2
F4
F5
Acceleration (g)
Y-direction
F1
F2
F4
F5
F3
F6
Additional
peaks in yF3
direction
for 3D
input
F6
Analysis of Floor Spectra, LRB System
3D Input
Floor Spectra for Diablo Canyon 80%, y-direction
3rd Structural Mode
Y-direction
T = 0.1 sec
3rd Structural Mode
X-direction
T = 0.1 sec
Acceleration (g)
Floor 1
Floor 4
Floor 2
Floor 5
Period (sec)
Floor 3
Floor 6
Tools for Isolation and Protective Systems
Floor Acceleration Response in TPB
System, XY vs. 3D Motion
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
Floor Acceleration Response in TPB
System, 3D Takatori (Vert. PGA = 0.28g)
Mode 8
The acceleration
profile in X-dir
follows the 2nd
structural mode.
2nd Structural Mode
T = 0.17 sec
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Analysis of Floor Spectra, TPB System
3D Input
Floor Spectra for Takatori 100%, x-direction
Mode 8
2nd Structural Mode
T = 0.17 sec
Tools for Isolation and Protective Systems
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.
Quake Summit 2012
Boston, Massachusetts, July 12, 2012
Tools for Isolation and Protective Systems
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.
2012 Structures Congress
Chicago, Illinois, March 29-31, 2012
Tools for Isolation and Protective Systems
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)
2012 Structures Congress
Chicago, Illinois, March 29-31, 2012