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Aristotle University of Thessaloniki Department of Civil Engineering Laboratory of Soil Mechanics, Foundations & Geotechnical Earthquake Engineering Research Unit of Geotechnical Earthquake Engineering and Soil Dynamics. Time-dependent vulnerability assessment of RC buildings considering - PowerPoint PPT Presentation
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Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
Time-dependent vulnerability assessment of RC buildings considering
SSI and aging effects
Aristotle University of ThessalonikiDepartment of Civil Engineering
Laboratory of Soil Mechanics, Foundations & Geotechnical Earthquake EngineeringResearch Unit of Geotechnical Earthquake Engineering and Soil Dynamics
COMPDYN 2013, Kos Island, Greece June 2013
Sotiria Karapetrou
Argyro Filippa
Stavroula Fotopoulou
Kyriazis Pitilakis
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
Methodological framework
Selection of reference structures• Low and
medium rise RC frame buildings
• Modern seismic code design
Simulation of the structural models under study• Fiber based
approach• SSI• Corrosion
probabilistic models
Non-linear dynamic analysis
• 8 different outcropping real records
• Response parameter: maxISD(%)
Time-dependent fragility curves• IM: PGA• LS in terms
of maxISD(%)
• Incorporation of uncertainties
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 3
Structural models
2-storey, 1-bay RC MRF building
Designed based on Greek modern seismic code
Material properties: Concrete C20/25 Steel B500C
Fundamental period: T1=0.3936sec
Gelagoti (2010)
Low-rise structural model
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 4
Structural models
4-storey, 3-bay RC MRF building
Designed based on
modern seismic code of Portugal
Material properties: Concrete fc=28MPa Steel fy=460MPa
Fundamental period: T2=0.5018sec
Abo El Ezz (2008)
4Φ18
+4Φ16 3Φ16+5Φ12+2Φ10
3Φ16+5Φ12+2Φ10
3Φ12+6Φ10
3Φ12+6Φ10
Mid-rise structural model
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
Finite element code OpenSees Material inelasticity Distributed material plasticity (fiber based approach)
Unconfined concrete:
Kent and Park model (1971)
Confined concrete:
Modified Kent and Park model
(Scott et al 1982)
Steel:
uniaxial bilinear steel material
object with kinematic hardening
Numerical modeling
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 6
Schematic view of the applied approaches
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 7
Soil-structure interaction (SSI) modelingSSI two-step analysis (Fotopoulou et al. 2012) 1st step: 1D equivalent linear analysis of the soil column 2nd step: Impedance function by Mylonakis et al. (2006)
CyberQuakeG-γ-D by Darendeli (2001)
Vs,30=300m/sec
→ free field surface motion
→ effective shear strain of the surface layer γeff
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 8
Soil-structure interaction (SSI) modelingSSI two-step analysis (Fotopoulou et al. 2012) 1st step: 1D equivalent linear analysis of the soil column 2nd step: Impedance function by Mylonakis et al. (2006)
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
Calibration of the soil parameters in terms of G = f(γ) και D(%) = f(γ) based on1D equivalent linear analysis conducted in Cyberquake for the SSI two-step analysis
Lysmer-Kuhlemeyer (1969) dashpot
Input Motion
Rigid beam-column element
30.0
m
Soil-structure interaction (SSI) modeling
Elastic Bedrock Vs=1000m/sec
120.0m
30.0
m
OpenSees
SSI one-step analysis
Free field
Soil profile 120m x 30m, 3600 four node quadrilateral elements Soil quad element 1m x 1m
Elastic soil layers Vs,30=300m/sec
Common nodes-Apropriate constraints
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
30.0
m
Soil-structure interaction (SSI) modeling
Soil profile 120m x 30m, 3600 four node quadrilateral elements
Soil quad element 1m x 1m
SSI one-step analysis
Lysmer-Kuhlemeyer dashpot at the base
Elastic soil layers
Calibration of the soil parameters in terms of G = f(γ) και D(%) = f(γ) based on1D equivalent linear analysis conducted in Cyberquake for the SSI two-step analysis
Elastic bedrock Vs=1000m/sec
Soil – structure: common nodes, appropriate constraints
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 11
Main parameters: W/C, Ccrit, Tini, icorr, Di, n
Probabilistic modeling of corrosion initiation time due to chloride ingress according to FIB-CEB Task Group 5.6 (2006)
Time-dependent loss of cross sectional area of reinforced bars based on Gosh και Padgett (2010)
Corrosion modelingCorrosion scenario for the t=50 years
Distribution of Chloride corrosion initiation time Tini
mean = 2.96 years Standard Deviation = 2.16 years
2i init
2
init
n D if t T4
A( t )max n D t ,0 if t T
4
i init
i corr init init
D if t TD( t )
max[ D i ( t T ),0 ] if t T
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 12
Nonlinear Dynamic Analysis 2D nonlinear time-history analysis for t=0 and 50 years
8 outcropping records corresponding to sites classified as rock or stiff soil according to EC8
3 scaling levels in terms of PGA: 0.1g 0.3g 0.5g
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
Ghobarah (2004) : max ISD(%) for ductile and non-ductile MRF systems
Scenario t=0 years: damage states for MRF – ductile structures Scenario t=50 years: damage states for MRF – non-ductile structures
Damage states Ductile MRF Non-ductile MRF
Light damage 0.4 0.2
Moderate damage 1.0 0.5
Severe damage 1.8 0.8
Collapse > 3.0 > 1.0
Definition of Damage States
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
Ghobarah (2004) : max ISD(%) for ductile and non-ductile MRF systems
Scenario t=0 years: damage states for MRF – ductile structures Scenario t=50 years: damage states for MRF – non-ductile structures
Damage states Ductile MRF Non-ductile MRF
Light damage 0.4 0.2
Moderate damage 1.0 0.5
Severe damage 1.8 0.8
Collapse > 3.0 > 1.0
Definition of Damage States
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 15
ttmPGAPGADSP
lnln/
t : reference time
Lognormal distribution
Time-dependent fragility curves
m(t), β(t): PGA median values and logarithmic standard deviations at different points in time t along the service life (t=0 and 50 years)
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 16
Uncertainties
222dsCD
βD: demand (variability in the numerical results)
βC: capacity (HAZUS)
βds: definition of damage state (HAZUS)
Time-dependent fragility curves
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 17
0 0 .2 0 .4 0 .6
0
1
2
3
4
5
da taS lig h t d am ag eM o d e ra te d am ag eE x ten siv e d am ag eC o m p le te d am ag eP o w e r f it
y = 5 .9 7 5 3 x 0 .9 4 9 9R 2 = 0 .7 9 1 8
L o w r ise - flex ib le b a se - V s= 3 0 0 m /sec , t= 5 0 y ea rs
P G A (g )
ISD
max
(%)
0 0 .2 0 .4 0 .6
0
1
2
3
4
d a taS lig h t d am ag eM o d e ra te d am ag eE x ten s iv e d am ag eC o m p le te d am ag eP o w er f it
y = 4 .4 3 6 5 x 0 .9 9 7 6R 2 = 0 .8 0 1 6
L o w r ise - fix ed b a se - ro ck , t= 5 0 y ea rs
P G A (g )
ISD
max
(%)
0 0 .2 0 .4 0 .6
0
1
2
3
4d a taS lig h t d am ag eM o d era te d am ag eE x ten s iv e d am ag eC o m p le te d am ag eP o w er f it
y = 3 .5 2 8 8 x 1 .0 2 4 3R 2 = 0 .8 6 5 6
L o w r ise - fix ed b a se - ro ck , t= 0 yea rs
P G A (g )
ISD
max
(%)
0 0 .2 0 .4 0 .6
0
1
2
3
4
5d a taS lig h t d am ag eM o d e ra te d am ag eE x ten siv e d am ag eC o m p le te d am ag eP o w e r f it
y = 4 .7 7 8 3 x 0 .8 9 6 9R 2 = 0 .8 4 8 7
L o w r ise - flex ib le b a se - V s= 3 00 m /sec , t= 0 y ea rs
P G A (g )
ISD
max
(%)
Fragility curves PGA-ISDmax (%) for the low rise structures considering fixed and
compliant condition for t=0 and 50 years
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
Comparison with literature
Low rise strucural model designed
based on modern seismic codes
(t=0 έτη)
Fragility curves
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects
Comparison with literature
Mid rise strucural model designed
based on modern seismic codes
(t=0 έτη)
Fragility curves
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 20
Fragility curves Low rise structural model
Aging effects→ Increase in vulnerability
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 21
Fragility curves Mid rise structural model
Aging effects→ Increase in vulnerability
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 22
Fragility curves Fixed and compliant (Vs=300m/sec) foundation conditions for t=0years
SSI and foundation compliance → Increase in vulnerability
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 23
Fragility curves Fixed and compliant (Vs=300m/sec) foundation conditions for t=0years
SSI → Decrease in vulnerability
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 24
Fragility curves Substructure (two-step) and direct (one-step) methods for SSI modeling
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 25
Fragility curves Percentage increase in vulnerability due to soil compliance
1 2 3 4D am age s ta tes
0
2 0
4 0
6 0
8 0
1 0 0
Perc
ent i
ncre
ase
(%) o
f vul
nera
bilit
y
4 9 .3 49 .8 50 .1 50 .347 .540 .1
35 .230 .2
T w o -s te p ap p ro achO n e-s tep ap p ro ac h
D S D S D S D S
L o w -r ise stru ctu ra l m o d el
1 2 3 4D am age s ta tes
0
2 0
4 0
6 0
8 0
1 0 0
Perc
ent i
ncre
ase
(%) o
f vul
nera
bilit
y
3 236 .9
40 .1 42 .6
28 .8 27 .3 26 .6 25 .7
T w o -s te p ap p ro achO n e-s tep ap p ro ach
D S D S D S D S
M id -r ise stru ctu ra l m o d el
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 26
Fragility curves
1 2 3 4D am age s ta tes
0
1 0
2 0
3 0
4 0
Perc
ent d
ecre
ase
(%) o
f vul
nera
bilit
y
0 .68 0 .73 0 .78 0 .81
16 .1
9 .16
4 .94
1 .3
T w o -s te p ap p ro ac hO n e-s te p ap p ro ac h
D S D S D S D S
L o w -r ise s tru ctu ra l m o d el
1 2 3 4D a m ag e s ta tes
0
1 0
2 0
3 0
4 0
Perc
ent d
ecre
ase
(%) o
f vul
nera
bilit
y1 .7
3 .1 4 4 .83 .5 9
11 .8
17 .2
22 .3
T w o -s te p ap p ro achO n e -s tep ap p ro ac h
D S D S D S D S
M id -r ise stru ctu ra l m o d el
Percentage decrease in vulnerability due soil-structure interaction
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 27
Conclusions
aging effects :
affect the dynamic response and the seismic vulnerability of the
structures
corrosion of reinforcement :
is considered as a loss of cross sectional area of reinforced bars
leads to significant increase of structure vulnerability due to the
considered “worst case scenario”
soil deformability and soil compliance :
modify the structural response of the analyzed structures resulting to
higher vulnerability values.
depends on: the characteristics of the building, the input motion and
the soil properties.
Laboratory of Soil Mechanics, Foundations and Geotechnical Earthquake Engineering, AUTH
Time-dependent vulnerability assessment of RC buildings considering SSI and aging effects 28
Conclusions
soil-foundation-structure interaction (SFSI): leads to decrease in structural vulnerability
the uncoupled two-step approach (substructure method) leads to higher
vulnerability (overestimation due to uncertainties related, among others, to
the evaluation of the impedance function)
further research in:
definition of limit states for corroded structures based on adequate
analytical, experimental and empirical data
incorporation of the fully probabilistic models within the dynamic analysis