nonlinear performance and potential damage of degraded structures under different earthquakes the 5...
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![Page 1: Nonlinear Performance and Potential Damage of Degraded Structures Under Different Earthquakes The 5 th Tongji-UBC Symposium on Earthquake Engineering “Facing](https://reader030.vdocuments.site/reader030/viewer/2022032702/56649f485503460f94c6a778/html5/thumbnails/1.jpg)
Nonlinear Performance and Potential Damage of Degraded Structures Under Different Earthquakes
The 5th Tongji-UBC Symposium on Earthquake Engineering “Facing Earthquake Challenges Together” May 4-8 2015, Tongji University Shanghai, China
Case study of ground motion and response spectra comparison of the Wenchuan (2008) and Lushan (2013) earthquakes
Yuxin PanStructural & Earthquake Engineering / Dr. Carlos E Ventura
M.Phil | The Hong Kong University of Science and Technology, Hong Kong (2012)
PhD Candidate | The University of British Columbia, Canada (2013 - Present)
May 7th, 2015
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Background & Objectives
General Seismicity of Selected Stations
Numerical Model of Equivalent SDOF System
Analysis Results & Discussions• Inelastic hysteretic response
• Arias intensity vs. drift limit
• Elastic & inelastic response spectra
Conclusions & Future Works
Outline
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Research background
Crustal EQs
Intraplate EQs
Interplate EQsCascadia Seismic Sources
Historical Eqs in Canada
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SI_for_Kobe 72 SI_for_Llayllay 81
cm Max_DiplacementLlayllay 15cm Max_Diplacement_Kobe 20
0 10 20 30 40 50 60 7020
10
0
10
20
Time (s)
Dis
plac
emen
t (cm
)
0 10 20 30 40 50 60 7020
10
0
10
20
Time (s)
Dis
plac
emen
t (cm
)
cm / sMax_Velocity_Kobe 74cm / sMax_Velocity_Llayllay 73
0 10 20 30 40 50 60 70100
50
0
50
100
Time (s)V
eloc
ity (
cm/s
)
0 10 20 30 40 50 60 70100
50
0
50
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Time (s)
Vel
ocity
(cm
/s)
cm/s2 Max_Acceleration_Llayllay 605cm/s2 Max_Acceleration_Kobe 587
0 10 20 30 40 50 60 701000
500
0
500
1000
Time (s)
Acc
eler
atio
n (c
m/s
/s)
0 10 20 30 40 50 60 701000
500
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Time (s)
Acc
eler
atio
n (c
m/s
/s)
Crustal Eq. vs Subduction Eq.
1995 Kobe eq. 1985 Chile eq.
Research background
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Research background
0.5 1 1.5 2 2.5 3 3.5 40
0.5
1
1.5
2
2.5
KOBELLAYLLAY
Spectral Acceleration (g)
T (sec)
SA
(g)
0.5 1 1.5 2 2.5 3 3.5 40
50
100
150
200
250
300
KOBELLAYLLAY
Spectral Velocity (cm/s)
T (sec)
SV
(cm
/s)
0.5 1 1.5 2 2.5 3 3.5 40
10
20
30
40
50
60
KOBELLAYLLAY
Spectral Displacement (cm/s)
T (sec)
SD
(cm
)
5% damping
Crustal Eq. vs Subduction Eq.
SA spectra
SV spectra SD spectra
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Research background
Rule Based Hysteretic Models & Backbone Curves
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Research background
Arias Intensity
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Research background
Directivity is an effect of a fault rupturing whereby earthquake ground motion in the direction of rupture propagation is more severe than that in other directions from the earthquake source.
8
5249150 0 150
150
150Particle Velocity (cm/s)
E/W direction
N/S
dire
ctio
n
150 0 150
150
150Particle Velocity (cm/s)
E/W direction
N/S
dire
ctio
n
200 0 200
200
200Particle Displacement (cm)
E/W direction
N/S
dire
ctio
n
S 1
200 0 200
200
200Particle Displacement (cm)
E/W direction
N/S
dire
ctio
n
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Research background
Fig. Intensity map for Wenchuan and Lushan EQs
In 2008, there was an big earthquake with Mw of 7.9 occurred in Wenchuan, Sichuan Province of China. Five years later, in 2013, another earthquake with Mw of 7.0 took place at the same region (Lushan, Sichuan Province) along the Long Men Shan fault.
Wenchuan Earthquake (2008):Epicenter: 31.000N 103.400E Depth: 14 KM Duration: 350 SEC
Lushan Earthquake (2013): Epicenter: 30.299N 103.000E Depth: 13 KM Duration: 80 SEC
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Objectives
This study mainly analyzed the ground motion records at same stations from both earthquakes, and compared the elastic and inelastic response spectra for a typical SDOF in-filled reinforced concrete (RC) structure by considering the stiffness and strength degradation. Response of different capacity levels’ structures (100% Fy, 75% Fy, … 10% Fy) will also be investigated.
Four main stations were selected for comparison, both east-west (EW) and north-south (NS) ground motions were analyzed, as seen in Figure. They are 51YAM, 51LSF, 51QLY and 51YAL. These four stations recorded the maximum PGA of Lushan Earthquake.
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Fig. Elastic spectra comparison
Fig. Arias Intensity and significant duration (5%-95%)
Elastic spectra & Arias intensity
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Directivity
12
51LSF
Location 30.021N 102.895E
Site Condition Soil
Distance to Wenchuan Epicenter
119.3 KM
PGA of Wenchuan EQ 124.1 CM/S2 (EW)
Distance to Lushan Epicenter 32.6 KM
PGA of Lushan EQ 387.4 CM/S2 (EW)
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13
51QLY
Location 30.407N 103.266E
Site Condition Soil
Distance to Wenchuan Epicenter 67.2 KM
PGA of Wenchuan EQ 199.8 CM/S2 (NS)
Distance to Lushan Epicenter 28.2 KM
PGA of Lushan EQ 315.5 CM/S2 (NS)
Directivity
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Equivalent SDOF System
Experimental Test
Reinforced Concrete Partially Infilled Frames; OpenSees modeling: Hysteretic material; Strength and stiffness degradation; No pinching effect was considered; 10% collapse drift limit
Reference: Anil, Özgür, and Sinan Altin. "An experimental study on reinforced concrete partially infilled frames." Engineering Structures 29.3 (2007): 449-460.
-0.06 -0.04 -0.02 0 0.02 0.04 0.06-600
-400
-200
0
200
400
600
Hysteretic Curve of Equivalent SDOF
Fy0.75Fy0.5Fy
Rotation
Mom
ent
Zerolength element
Rigid column
Mass
Numerical model in OpenSees
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Inelastic hysteretic response
51YAM_Lushan_EW
51YAM_Wenchuan_EW
Short Period (T=0.5s)
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51YAM_Lushan_EW
51YAM_Wenchuan_EW
Medium Period (T=1.0s)
Inelastic hysteretic response
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Inelastic hysteretic response
51YAM_Lushan_EW
51YAM_Wenchuan_EW
Long Period (T=2.0s)
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Drift limit vs. Significant duration
51YAM_Lushan_EW 51YAM_Wenchuan_EW
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Elastic & inelastic response spectra
For each station, both N-S and E-W directions were studied. The design earthquake spectra and rare earthquake spectra (2% in 50 years)
based on Chinese Code for Seismic Design of Buildings (CCSDB) were also plotted for comparison.
CCSDB 51YAM 51LSF 51QLY 51YAL
Design Intensity 7 7 7 7
Design EQ Acceleration 0.10g 0.15g 0.10g 0.15g
Rate EQ Acceleration 0.50g 0.72g 0.50g 0.72g
Characteristic Period 0.45s 0.40s 0.45s 0.45s
Site Category II II II II
Design EQ Category 3rd 2nd 3rd 3rd
Damping Ratio 5%0 0.5 1 1.5 2 2.5 3 3.5 4
0
0.3
0.6
0.9
1.2
1.5
Design Acceleration from CCSDB
Design EQ - 51LSFRare EQ - 51LSFDesign EQ - 51YAMRare EQ - 51YAM
Period (s)
Sa (g
)
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Elastic & inelastic response spectra
51YAM (N-S)
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Elastic & inelastic response spectra
51LSF (E-W)
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Conclusions
For the four selected stations, the Lushan Earthquake has much higher PGA, but larger drift demands resulted from the Wenchuan Earthquake;
Both elastic and inelastic spectra from Lushan Earthquake are higher than the local design spectra, and could be higher than rare earthquake spectra;
Overall, long period structures have larger displacements, but this trend varies with different capacity levels;
For the Wenchuan Earthquake, as expected, elastic system performed better than those weaker systems. However, for the Lushan Earthquake, elastic systems generated larger displacement at different period ranges.
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Future work
Sensitivity Studies
• Degradation• Capacity level
Structures• Gravity system• High-rise building• Incremental Dynamic Analysis (IDA)
Ground Motion
• Ground motion characteristics• Ground motion Selection & Scaling
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Thank you
Certificate of Structural Engineering Program