Tools for Isolation and Protective Systems Quake Summit 2012 Boston, Massachusetts, July 12, 2012...

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


Quake Summit 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


Quake Summit 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


Quake Summit 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


Quake Summit 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.


Quake Summit 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


Quake Summit 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.


Quake Summit 2012


Triple Pendulum (TPB) Isolators and Configuration

1.4 m (55 in)

.33 m(13 in)

9 isolators, one beneath each column


Quake Summit 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


Quake Summit 2012


5 cross linear bearings

4 lead rubber bearings

LRB/CLB System Configuration


Quake Summit 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)


Quake Summit 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


Quake Summit 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


Quake Summit 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,


Quake Summit 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


Quake Summit 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


Quake Summit 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


Quake Summit 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


Quake Summit 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


Quake Summit 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


Quake Summit 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


Quake Summit 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


Quake Summit 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


Quake Summit 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.


Quake Summit 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


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)



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)



Analysis of Floor Spectra, LRB System 3D Input

3rd Structural ModeY-directionT = 0.1 sec

3rd Structural ModeX-directionT = 0.1 sec


Quake Summit 2012


Floor Acceleration Response in TPB System, XY vs. 3D Motion


Quake Summit 2012


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.

Floor Spectra for Takatori 100%, x-direction

Analysis of Floor Spectra, TPB System 3D Input

Mode 8



Quake Summit 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.


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.


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)

Tools for Isolation and Protective Systems Quake Summit 2012 Boston, Massachusetts, July 12, 2012...

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