Nonlinear Performance and Potential Damage of Degraded Structures Under Different Earthquakes The 5 th 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 Pan Structural & 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 7 th , 2015
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Nonlinear Performance and Potential Damage of Degraded Structures Under Different Earthquakes The 5 th Tongji-UBC Symposium on Earthquake Engineering “Facing.
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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)
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.
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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
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.
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.
Fig. Elastic spectra comparison
Fig. Arias Intensity and significant duration (5%-95%)
Elastic spectra & Arias intensity
Directivity
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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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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
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
Inelastic hysteretic response
51YAM_Lushan_EW
51YAM_Wenchuan_EW
Short Period (T=0.5s)
51YAM_Lushan_EW
51YAM_Wenchuan_EW
Medium Period (T=1.0s)
Inelastic hysteretic response
Inelastic hysteretic response
51YAM_Lushan_EW
51YAM_Wenchuan_EW
Long Period (T=2.0s)
Drift limit vs. Significant duration
51YAM_Lushan_EW 51YAM_Wenchuan_EW
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.
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.