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