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Ambient Vibration Tests and Model Updating of the Health Sciences
Parkade at UBC
ILARIA CAPRAROSupervisor: Dr. Carlos E. Ventura
MASc | University of Bologna, Italy (2012)
PhD Student | The University of British Columbia, Canada (2014 - Present)
The 5th Tongji-UBC Symposium on Earthquake Engineering “Facing Earthquake Challenges Together” May 4-8 2015, Tongji University Shanghai, China
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Outline• Description of the Health Sciences Parkade;
• Two different Ambient Vibration Tests: Normal operational conditions; Almost empty environment;
• Modal frequencies and mode shapes evaluation;
• Comparison between the results obtained with the two different tests;
• Sensitivity analysis and modal updating;
• Examples of seismic retrofits on the Parkade;
• Conclusions and future work.
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Description of the HSPTwo 4-storey reinforced concrete buildings; Sets of three ramps each level; LFRS: shear walls and Moment Resisting Frame; External shear walls introduce stiffness irregularity
in elevation and “short column” effect.
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Main Lateral Force
Resisting System
External Shear Walls and
“Short Columns effect”
FE Models developed with SAP2000
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Complete AVT-Setups Configuration-
• 9 wireless Tromino sensors;• 5 setups;• Recording duration: 40 mins;
• Sampling frequency 256 Hz;• GPS synchronization;• Operational conditions → high levels of traffic.
Reference Sensor
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ARTeMIS Model
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Frequency Domain Analysis
FDD: Frequency Domain Decomposition• Vertical channels not included in the analysis;• Re-sampling at 128 Hz;• 1024 frequency lines;• Decimation: 0 – 32 Hz;• Six modes identified up to 8 Hz.
Time Domain Analysis
SSI-UPC: Stochastic Subspace Identification• Natural frequencies and modal damping values evaluated;• High values for modal damping;
← Stabilization diagram for Setup 4.
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1st Mode Shape: 2.756 HzN – S Longitudinal
N - S
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T
2nd Mode Shape: 3.894 HzTorsional
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E - W
3rd Mode Shape: 4.413 HzE – W Transversal
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T
4th Mode Shape: 5.781 HzTorsional
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Mode #Frequency [Hz]
CommentFDD
1 2.7561 st N-S Longitudinal
2 3.894 1 st Torsional
3 4.4131 st E-W Transversal
4 5.781 2 nd Torsional
5 7.2442 nd N-S Longitdinal
6 7.9443 rd N-S Longitudinal
Summary of the Results
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AVT in almost empty environment• Just the reference sensor used at the same location as previously;• Test performed late in the day;• Recording duration and sampling frequency same as the complete AVT.
Reference Sensor
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Comparison between the two AVTs
•1st natural frequency is ~ 12% higher when traffic is present;• Vertical component of vibration is predominant between 10-20 Hz;• Strong amplification due to traffic load;• The change in mass between the two tests did not affect significantly the natural frequencies of the structure.
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Sensitivity Analysis6 Responses: • Natural frequencies.
22 Parameters:• Rho: material density of
slabs;• E: elastic Modulus of shear
walls;• H: shear wall thickness.
Sensitivity Matrix, FEMtools V3.8 →
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Model Updating Results
Mode
AVT SAP2000 FEMtools updatedDescriptio
nFrequency [Hz]
Frequency [Hz]
Difference
Frequency [Hz]
Difference
1 2.756 2.58 6.3 % 2.68 2.7 %1st N-S
Longitudinal
2 3.875 3.56 8.1 % 4.15 7.2 % 1st Torsional
3 4.413 4.58 3.8 % 5.47 23.9 %1st E-W
Transversal
4 5.781 6.72 16.3 % 6.70 15.9 % 2nd Torsional
5 7.250 8.17 12.7 % 7.30 0.7 %2nd N-S
Longitudinal
6 7.931 7.98 0.7 % 8.03 1.2 %3rd N-S
Longitudinal
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Conclusions and future work
1st natural frequency at 2.756 Hz corresponding to a fundamental longitudinal mode in N-S direction;
The first torsional mode is about 1 Hz higher than the fundamental mode. The HSP is likely to experience both lateral and torsional responses;
Comparing the results from the two AVTs, the mass of the cars seems not to affect significanlty the dynamic properties of the HSP;
Strong amplification of vibrations due to traffic loads. After model updating, general increase of E and H was
observed; The stairwells were proved to contribute significantly to the
dynamic behaviour of the structures as their thickness increased of about 150%.
Little information on the contribution of the ramps to the dynamic behaviour of the HSP due to limited number of sensors.
AVT repeated in March 2015 after seismic retrofit.
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ANY QUESTIONS?
Thank you!
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Certificate of Structural
Engineering Program