Basic Concept of Base Isolation System for Buildings
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Transcript of Basic Concept of Base Isolation System for Buildings
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Basic Concept of Base Isolation
System for Buildings
Dr. Taiki SAITO
Japan Society of Seismic Isolation
Chief Research Engineer,
Building Research Institute, Japan
Email: [email protected]
Contents
Introduction
Basic Idea of BI system
Design procedure of BI building
Response spectrum method
Time history analysis
Ultimate capacity of isolators
International activity of JSSI
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Basic Idea of BI system
Isolation from ground
By balloon? By Magnetic force?
Introduction
Seismic isolation
Rolling? Sliding?Stopper Friction
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Introduction
Example of sliding system
Kamakura statue was rehabilitated in 1960 adopting sliding foundation.
Introduction
Restoring position?
Sliding?
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Introduction
Restoring system
By spring? By sliding on a
curved plate?
IntroductionGravity Force and Inertia Force
Resisting Force
k
mT 2=
g
LT 2=
(m: mass, k: stiffness)
Effective for heavy building(L: curvature, g: gravity acceleration)
Effective for light building
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Introduction
d0
time
T
d0
With Damper
Damping system
Damper
Introduction
Requirement of BI devices
1. Isolating the building from the ground
2. Supporting the weight of building
3. Damping of response amplitude
4. Restoring the original position after an earthquake
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Introduction
Isolators
Rubber bearingLarge axial deformation
Weight ofbuilding
Rocking
Rubber lock
Stiff
Rubber
Earthquake
Load
Soft
Steel
Laminated Rubber
Weight of
building
-500
-400
-300
-200
-100
0
100
200
300
400
500
-300 -200 -100 0 100 200 300
Displacement (mm)
Force(kN)
High damping rubber
Reinforcing steel plate
Cover rubber
Flange plate
High damping rubber
Reinforcing steel plate
Cover rubber
Flange plate
-2
-1
0
1
2
-3 -2 -1 0 1 2 3
Shear
stress(N/mm
2)
-800
-600
-400
-200
0
200
400
600
800
-300 -200 -100 0 100 200 300
Displacement (mm)
Force(kN)
Natural Rubber Bearing
(NRB)High-damping Rubber
Bearing (HRB)
Lead Rubber Bearing
(LRB)
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Introduction
Isolators
Sliding bearing or Roller bearing
Linear Rail
Linear BlockRubber Shim
Flange Plate
Sliding bearing
Curved plane
sliding bearing
-50
-40
-30
-20
-10
0
10
20
3040
50
-150 -100 -50 0 50 100 150
Displacement (mm)
Force(kN)
-200
-150
-100
-50
0
50
100
150
200
-4 00 - 30 0 -2 00 - 100 0 1 00 2 00 30 0 4 00
Displacement (mm)
Force(kN)
Rail roller bearing
Introduction
Dampers
Cast Lead
Steel Flange Plate
Steel Damper Rod
Steel Flange Plate
Stud
F =1150(kNs/m) V0.38
- 20 - 15 - 10 -5 0 5 10 15 20( cm)
(kN)
800
600
400
200
0
-200
-400
-600
-800
Lead damper
Viscous damper
Steel damper
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Introduction
Response of BI building
STERA 3D
Introduction
Response of BI system
Y"
X
Upper structure
(rigid mass)
Base Isolation level
(spring)
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Introduction
Response of BI system
Y"
X
- m(X"+Y" )
Q=keX
c X'
Vibration model Equilibrium of forces
M X + CX + Ke X = - MY
Numerical integration
X + 2h X + 2 X = - Y
= (2 /T) = (Ke/M)
T: natural period
h : damping factorY X
X
X
Equation of motion
Introduction
Effect of natural period Y: JMA-Kobe NS componenth = 0.05
T longer
Displacement larger
T longer
Accelerationsmaller
X
X
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Introduction
Response spectrum
Time history of accelerationResponse spectrum of acceleration for
JMA Kobe-NS wave, h=0.05
Response of
SDOF system
with naturalperiod of T &
viscous damping
ofh
X
Y
T longer
Accelerationsmaller
Introduction
Effect of damping JMA Kobe-NS wave
Acceleration response spectrum Displacement response spectrum
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Introduction
Reduction of applied
lateral forces to super
structure
Increase of displacement
response of isolated story
Contents
Introduction
Idea of BI system
Design procedure of BI building
Response spectrum method
Time history analysis
Ultimate capacity of isolators
International activity of JSSI
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Design procedure of BI building
Statistics Number of buildings
Private house
Apartment building
1995 The Great Hanshin-
Awaji Earthquake Disaster
2000 Revision of
Building Standard Law
Design procedure of BI building
Building Standard Law, Japan
Height>60m
NO
YES
Reviewed by local government official Reviewed by
special committee
Response Spectrum Method Time History Analysis
Need for Structural Calculation?
YES
NO
Specification code
1 or 2 story wooden house1 story S or RC building
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Design procedure of BI building
Response Spectrum Method
Upper structure
(elastic range)
Base Isolation level
(inelastic range)
Force
Drift
Force
Drift
Ke
he
Ke: equivalent stiffness
he : equivalent damping
Responses are obtained by equivalent linearization.
Nonlinear system Equivalent linear system
he
he
h=0.05
h=0.05
Te
Te
Acceleration response
Displacement response
cm/s2
cm
s
s
Response evaluation
Design procedure of BI building
Time History Analysis
cm/s2
s
Artificial earthquake compatible with design spectrum
Three different
phase models
cm/s2
s
Historical earthquake scaled to have the max. velocity 50cm/s
El Centro1940NS,
Taft 1952EW,
Hachinohe1968EW,
etc.
cm/s2
s
Site specific artificial earthquake
Wave generation
from the nearest
Fault, etc.
cm/s2
s
Bedrock
5% damping
cm/s2
s
Bedrock
5% damping
Earthquake response is obtained
by time history analysis
(numerical integration method)
using design earthquake ground
motions.
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Design procedure of BI building
Time History AnalysisBuilding is modeled by MDOF nonlinear hysteresis system.
Sway
Rocking
RFL
10FL
9FL
8FL
7FL
6FL
5FL
4FL
3FL
2FL
Living Kitchen
10F
FL
8FL
7FL
6FL
5FL
4FL
3FL
2FL
1FL
Isolator Isolator Isolator
RFL
,800 6,000 2,700
15,500960 950
Y Y2 Y3
30,7
9
29,9
9
3,5
50
2,
860
2,8
60
GL
600
600
800
Responses are obtained by numerical integration method.
Design procedure of BI building
Confirmation of ultimate limit state
Example. LRB
Diameter: 800mm
Rubber sheet: 5.1mm
Number of sheets: 33
Rubber height: 168mm
Design criteria
21N/mm2
Design criteria
240% 168 = 403mm =
Compression stress (N/mm2)
Shear strain (%)
a. Allowable deformation of isolation device
b. Compressive and tensile load of isolator
c. Isolation gap (horizontal and vertical)
Isolation gap
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Design procedure of BI building
Ultimate capacity of isolators
Ultimate Shear Test
(from Prof. Nishi, Tokyo Institute of Technology, Japan)
Ultimate Compression Test
Contents
Introduction
Idea of BI system
Design procedure of BI building
Response spectrum method
Time history analysis
Ultimate capacity of isolators, etc.
International activity of JSSI
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International Activity of JSSI
CIB/W114
As one of the working
commissions in CIB
(International Council for
Research and Innovation
in Building and
Construction), W114:
Earthquake Engineering
and Buildings has been
established since
November 2006 .
Headquarter: JSSI
Coordinator: Taiki SAITO
http://www.cibw114.net/
International Activity of JSSI
CIB/W114The first CIB/W114 meeting, "International Workshop on Response Control and Seismic
Isolation of Buildings," was held in Guangzhou, China on 27 November 2006.
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International Activity of JSSI
CIB/TG44 bookContents
1. Introduction
2. Devices for Seismic Isolationand Response Control
3. A Comparative Study of
Seismic Isolation Code
Worldwide4. Observed Response of
Seismically Isolated Buildings
5. World Report
5.1 China5.2 Italy
5.3 Japan
5.4 Korea
5.5 New Zealand
5.6 Taiwan
5.7 The United of America
6. Conclusions
published in November 2006
China from Dr. Zhou Fulin adn Dr. Wen Liuhan
Around 600 base isolation buildings have been constructed. The
one was constructed in 1991.
35 base isolation buildings are constructed on the two-story reinforced concreteplatform of subway station in Beijing, China.
Base isolators at the large span structure of theShanghai F1 circuit.
Miniature building modelsfor shaking table test
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Italy from Mauro Dolce, Massimo Forni and Alessandro Martelli
60
50
40
30
20
10
0
1981 1986 1991 1996 2001 2006
Currently, there are
only two seismically
isolated buildings in
Korea, with a third to
be built soon.
The Unison Research
and Development
Center building,
constructed in 1997,
was the first
seismically-isolated
building.
Korea from Dong Guen Lee
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The second was
Traum Hous III, a 12-
story apartment
building in Seoul
Korea from Dong Guen Lee
The first seismically
isolated structure in
New Zealand was the
Motu Bridge in the
North Island
completed in 1974.
New Zealand from John X. Zhao
The isolation mechanism is provided by
stepping action of each of the two feet
of the piers. Steel dampers are used for
energy dissipation.
Rocking Seismic Isolation System
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Construction of the first seismically-isolated building in the
USA was completed in 1985, and by mid-2005 there were
approximately 80 seismically-isolated buildings in the USA
USA from Ian Aiken and Andrew Whitaker
The first building in the
USA is the Foothill
Communities Law &
Justice Center, in Rancho
Cucamonga, California,
was completed in
1985,with 98 high-damping rubber bearings
located below the
basement level
USA from Ian Aiken and Andrew Whitaker
The second building
application in the USA
was the City and County
Building, in Salt Lake
City, Utah, completed in
1989 with 208 lead-rubberand 239 natural rubber
bearings.
This project was the first
in the world to use
isolation for retrofit,
completed in 1989.
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The USC University Hospital in
Los Angeles, completed in 1991,
was the first hospital in the world to
use seismic isolation with 68 lead-
rubber isolators and 81 natural-
rubber isolators.
USA from Ian Aiken and Andrew Whitaker
Roof
6th
4th
LowerFoundation
The 1994 Northridge earthquake
Macedonia from Garevski A. Mihai and James M. Kelly
Primary School Pestalozzi" in Skopje, the first structure in the world
base isolated by means of rubber bearings constructed in 1969
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Thank you for your attention.