Recent Advances in Seismic Rehabilitation of Reinforced · PDF file ·...
Transcript of Recent Advances in Seismic Rehabilitation of Reinforced · PDF file ·...
Recent Advances in Seismic Rehabilitation ofReinforced Concrete Buildings in Japan
Shunsuke SuganoGraduate School of EngineeringHiroshima University, Japan
NATO Istanbul WorkshopMay 30 – July 1 、、、、2005
Kobe Earthquake(Jan.17 1995)
State of Seismic Rehabilitation of Reinforced Concrete Buildings in Japan
Recent Advances in
ResearchDesignPractice
OUTLINE
・・・・ Most of severely damaged buildings were designed and constructed before 1981 when the design code (the building standard law) was revised to the present form.
・・・・ New buildings designed and constructed after 1981 generally behaved in a good manner.
・・・・ It was supposed that the damage would be significantly mitigated if seismic evaluation
and rehabilitation were advanced
Lessons Learned from 1995 Kobe Earthquake
Construction Year
Da
ma
ge
In
de
x D
100
80
60
40
20
0
1920 1930 1940 1950 1960 1970 1980 1990 2000
Major Damage
1981
Present Building Standard
Law
Damage Level
D≧≧≧≧50 D=10~50 D=5~10D<5
N=167
MajorMediumMinorLight
(Architectural Institute of Japan, 1997)
Damage to School Buildings in Kobe (1995)
Social Demands
・・・・ No disturbance to
building function
・・・・ No evacuation of
building occupants
・・・・ No change of building
design (facade)
・・・・ Short construction
period
Consideration when Selecting
Rehabilitation Techniques
・・・・ Effect on building function
(lighting, traffic line, usability)
・・・・ Hindrance associated with
construction (noise, vibration,
dust, chemical smell)
・・・・ Effect on foundation system (increased building weight)
・・・・ Construction cost and period
Demands for Seismic Rehabilitation
Seismic Strengthening Seismic Control
Seismic Isolation
Isolator
New
foundation
Damper
Brace
Shear wall orSteel brace
Type of Seismic Rehabilitation
Measures
(a) Sheet Jacketing (b) Strand Jacketing (c) Panel Jacketing
continuous fiber sheet
(carbon, aramid, glass)
existing column existing column
nonshrink mortar
carbonfiber
panel
carbon fiberstrand
connection sheet
existingcolumn
Column Jacketing with New Materials
8-Story Office BuildingSRC frame and wall structures
Constructed in 1967Strengthened with exterior
SRC frames (lower story) and steel braces (upper stories)
Construction 1996.3-1999.3
Strengthening by Exterior Structures
Seismic Isolation (Office Building)
Steel Frame with Damper
Column Jacketing and Steel Dampers
Steel Elasto-plastic Damper
Seismic Control
Recent Advances in Research
A Large Variety ofResearchers
Research ItemsPresentations
Response to Social DemandsConstruction under hard condition
Maintaining function of original structure
Accumulation of Research DataRehabilitation design
Design approval
Reinforced Concrete (RC)
Seismic Rehabilitation (SR)
SR/RC (%)
Research on Seismic Rehabilitation
Proceedings of Annual Convention ofthe Architectural Institute of Japan(AIJ)
((((%))))
0
50
100
‘98 ‘99 ‘00 ‘01 ‘02 ‘03 ‘04’66~
‘83
0
100
200
300
400
500
‘97‘96‘95
Nu
mb
er
of
Pa
pe
rs
M
P
R
h
R =δδδδ/ hM = PhDeflection angle R
Ben
din
gm
om
en
t M
My
Ry
Y
Mm
Rm
Point Y: yielding
N0.8Mm
Ru
Point M:maximum momentPoint N: ultimate displacement
M
Ductility factor µ =µ =µ =µ =Ru/Ry
Restoring Force Characteristics of Jacketed Columns
Building columnBridge columnBond failureShear failureLower limita/D ≦≦≦≦ 2.5a/D>2.5
Ult
ima
te d
isp
lac
em
en
t R
u (ra
d.) Ru=0.0040Vs/Vf+0.046
Strength Radio Vs(AIJ)/Vf
(Shear strength)/(Flexural Strength)
0 42 6 80
0.10
0.08
0.06
0.04
0.02
Continuous-fiber Jacketing
Ru=0.032Vs/Vf-0.001Ru=0.03(Vs/Vf-1)
Ductility of Columns Jacketed with Continuous-fiber Sheets (Japan Concrete Institute, 2000)
Survey of New Rehabilitation Techniques
l Answerers: General Contractors
Survey 1: 2000 38 (Buildings)
12 (Bridges)Survey 2: 2004 19 (Buildings)
21 (Bridges)
l Questions
1. Target (reduction of cost, work period, etc)
2. Object (column, pier, etc)3. Purpose of rehabilitation
(improvement of ductility,
etc)4. Outline of technique (what’s new,
how to evaluate, etc)
JCI Questionnaire Survey (2000, 2004)
Major general contractors have their
own R/D institute to develop design
and construction technologies.
Target of Technology Development(Buildings)
Survey 2000
1. Reduction of work term
2. Removal unnecessary3. Reduction of hindrance
(noise, vibration, fine particles, etc)
Survey 2004
1. Reduction of work term2. Removal unnecessary3. Reduction of cost
0
20
40
60
80
100
Designfriendly
Removal
unnecessary
Reduction of work space
Lightweight
Reduction
of noise,vibration,etc
Reduction ofcost
Reduction ofwork term
Others
Priority
Subject of Technology Development (Buildings)
Survey 2000
1. Isolated column2. Placing concrete wall3. Placing steel braces
Survey 2004
1. Placing steel braces2. Placing concrete wall3. Isolated column
Exterior structure
Placing steel
braces
Placing steelpanel wall
Placing
concrete wall
Shear wall
Beam
Column with
side walls
Isolated Column
Others
0
10
20
30
40
50Priority
Recent Advances in Design
Performance-based Design ApproachesTarget performance
Level of design earthquakesEvaluation of Performance
Accumulation of Research DataRehabilitation design
Design approval
0
10
20
30
40
50
60
70
80
90
100
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
Seismic Structural Index Is (2nd Screening)
Da
ma
ge
Gra
de
In
de
x D
Architectural Institute of Japan, 1997
Iso=0.6
Observed Damage
by Inspectors
Collapse or major
moderate
minor
light
Seismic structural index Is
Is = E0xSdxTEo=CxFC:strength indexF:ductility index
Sd:structural designindex
T:time indexDamage Level
D≧≧≧≧50 D=10~50 D=5~10D<5N=167
MajorMediumMinorLight
Seismic Structural Index Is vs. Damage Level(Architectural Institute of Japan 1997)
Iso: judgment index
PML 20%
PML=Probable Maximum Loss
Building Price\ 10 billion
Repair Cost\ 2 billion
PML =Max. Loss by 10% / 50yr EQ
Rebuilding Cost
Probable Maximum Loss (PML)
0.4 0.6 0.8 1.0 1.20
10
20
30
40
PML50
35 35
40
45
40
30
20
10
50% 25% 15%
10%
5%
((((Min. Level))))
(30%) (15%) (7%)
(5%)
(2%)Min. Total Cost
(Target Performance)
Exp
ecte
d T
ota
l C
ost
(Co
nstr
ucti
on
Co
st
+ D
am
ag
e R
isk)
Seismic Structural Performance
Seismic Structural Index (IS)
Rehabilitation
Cost
Target Performance for Seismic Rehabilitation
2700 8000 7360 7360 36803680 7360 7360 8000 2700 5300
29100 29100
26 1225
24 3
23 4
22 5
21
620
19 7
8
9
10
9‘
1413
11
12
10‘
15
16
17
18
正面玄関方向
Seismic Isolation
As-built
Isolator
A Case of Buddhist Temple in Tokyo
Performance-Based Design for Seismic Rehabilitation
Historical earthquakes around Tokyo
l Target Performance: No damage against the 0.8g earthquake (return period 3000 years).
l Measures to improve performance: To install seismic isolation devices to reduce the response forces to 1/3 – 1/10.
1111
10101010
100100100100
1000100010001000
10000100001000010000
100000100000100000100000
0000 200200200200 400400400400 600600600600 800800800800 1000100010001000 1200120012001200 1400140014001400
3000yr
800
Seismic hazardAcceleration (cm/s2)
Re
turn
Pe
rio
d (
yr)
Seismic hazard of the site
Design Earthquake and Target Performance
Recent Advances in Practice
Increased Number of ImplementationsPublic buildings
Private buildings
A Large Variety of Rehabilitation TechniquesSeismic Strengthening
Response Control
Change of Consciousness and Awareness A large number of implementations
Increased number of private buildings
before Kobe EQ
after Kobe EQ0
1000
2000
3000
4000
5000
6000
7000
Publicbuildings
Evaluation Rehabilitation0
1000
2000
3000
4000
5000
6000 Privatebuildings
Evaluation Rehabilitation
7000
Public buildings
Private buildings
0
1000
2000
3000
4000
5000
6000
7000
after KobeEQ (1995)
Evaluation Rehabilitation
before KobeEQ (1995)
Evaluation Rehabilitation0
1000
2000
3000
4000
5000
6000
7000
Implementation of Evaluation and Rehabilitation
Japan structural Consultants Association (JSCA), 2003
A University Building
Seismic Rehabilitation Considering Building Facade
RC壁増設
外付増設フレーム
フーチング
新設杭
増打柱 480×500 増打梁 500×900
増打壁 W300開口閉塞壁 W250
Exterior Frame
Concrete Wall
Footing
New Pile
Concrete Wall (W250)
Exterior column 480*500
Exterior Beam500*900
Concrete Wall (W300)
Seismic Rehabilitation Using Exterior SRC Frames
Exterior FrameFloor Plan
Exterior Frame
Behavior of Rehabilitated Building
A Case of Kobe Yusen Building Survived 1995 Kobe Earthquake (M=7.3) without Any Damage
Kobe Yusen Building Use: Office Structure: Steel Encased with Concrete Designed: 1918Seismic rehabilitation for preservation (maintaining building facade)
Strengthening of concrete frames with steel framesStrengthening of brick walls with concrete walls
Extension of foundation slabs Construction for seismic rehabilitation: 1993.10 – 1994.3 Event during the earthquake: No damage
Why Seismic Rehabilitation Is not Spread?
1. Less attractive than building or rebuilding (backward business).
2. Hesitation to invest for long return period events (no budget) .
3. Hard job for designer and constructor because of time consuming work.
4. Rehabilitation is impossible(significant change of the building)
Change of Consciousness to Make Seismic Rehabilitation Possible
1. Attractive job to save human life, to secure properties and to maintain earth environment.
2. Necessary expenses to secure the building safety against earthquakes.
3. Advanced skill is displayed. 4. Advanced techniques make the difficult
seismic rehabilitations possible.
Column Jacketing
Steel-plate Jacketing
Carbon-fiber Jacketing
12.0
10.0
8.0
6.0
4.0
2.0
0.0 1.0 2.0 3.0 4.0 5.0
μμμμ =1.92 Vs/Vf + 2.45
R2=0.935
Strength Ratio Vs/Vf
(Shear strength)/(Flexural strength)
Du
cti
lity
fa
cto
r μμ μμ
0.0Concrete Jacketing
Ductility of Columns Jacketed with Concrete (Japan Concrete Institute.2000)
0.0 2.0 4.0 6.0
0.06
0.04
0.02
0.00Steel-plate Jacketing
Ru=0.055Vs/Vf+0.0261
Ru=0.0074Vs/Vf+0.0353R2=0.539
Strength Ratio Vs/Vf
(Shear strength) / (Flexural strength)
Ult
ima
te d
isp
lac
em
en
t R
u (
rad
)
Ductility of Columns Jacketed with Steel-plates(Japan Concrete Institute.2000)
Research
Application
Research
Application
Max. probable EQ Safety margin check
Recorded and/or artificial
50 cm/sec or more
Recorded and/or artificial
65 cm/sec or more
SuperstructureInterstory drift <1/400
No yielding
Interstory drift <1/200
Sufficient margin to failure
IsolatorLateral displacement
< 200%
Lateral displacement
< 300% or more
Superstructure
Interstory drift <1/200
Sufficient margin of safety
to member failure
Interstory drift <1/100
Margin of safety to
member failure
Damping system
Sufficient margin of safety
to energy dissipation
capacity
Margin of safety to energy
dissipation capacity
Level of ground motion
Seismic
control
Seismic
isolation
Max.velocity of
ground motion
Design Criteria for Response Control Buildings
Low friction isolation bearing Stable anchorage of isolator
Wall type viscous damper Full scale test of setting isolator
Back-up Technologies
ü Ministry of Construction, March, 1999.ü Specific building: The building which is used by many people such as office,
school, hospital, etc. and which has three or more stories and floor area
1,000m2 or more.
900 ( 0.5)300 ( 0.4)600 ( 1.6)Demolished
or rebuilt
4,100 ( 2.4)200 ( 0.2)3,900 ( 4.1)Rehabilitation
implemented
14,600 ( 8.6)500 ( 0.7)14,100 (14.9)Rehabilitation
necessary
28,100 (16.5)1,200 ( 1.6)26,900 (28.3)Evaluation
performed
170,000 ( 100)75,200 ( 100)94,800 ( 100)Surveyed
buildings
TotalPrivate
Buildings
Public
Buildings
Seismic Evaluation and Rehabilitation of Specific Buildings (Survey of 1999)
( ) %