ambient vibration 1 slides

DETERMINATION OF SEIMIC VULNERABILITY USING AMBIENT AND FORCED VIBRATION TESTS

Ziya DalkilicAsst. Prof. Serdar Soyoz

Civil Engineering DepartmentBogazici University

Outline

Motivation

Seismic Retrofitting of the Building

Ambient Vibration Test

Forced Vibration Test Forced Vibration Test

Seismic Vulnerability Assessment

Conclusions

Seismic VulnerabilityHow confidently do we predict the actual

performance/reliability by the current practice?

Modal period and damping ratios are critical to

determine especially for non-ductile buildings.

Vibration-Based Health Monitoring

8.E-19

1.E-04

2.E-04

3.E-04

4.E-04

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3.E-18

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System IDModal

Parameters

-5.E-04

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Diagnostics

Decision

Motivation

Determination of modal parameters

Determination of change in the modal parameters due to increase in the applied force to the structure

FEM updating using identified modal parametersFEM updating using identified modal parameters

Determination of seismic vulnerability of the structure

ET-B Building Bogazici University

Seismic Retrofitting

Before Retrofit After RetrofitDimension(cm cm) Number

Dimension(cm cm) Adet

40 60 13

70 75 955 75 270 90 165 90 1

Before Retrofit After Retrofit

Dimension(cm cm) # Direction

Dimension(cm cm) # Direction

Columns Shear Walls

65 90 160 2 90 90 2

60 50 1 90 80 150 60 1 80 90 130 30 2 30 30 230 50 2 30 50 2

70 90 1

650 45 1 E-W

635 40 1 E-W

40 345 1 N-S

40 620 2 N-S

325 30 1 E-W 325 30 1 E-W

30 470 2 N-S 30 470 2 N-S

Instrumentation

Ambient Vibration Test

Modal Frequencies and Shapes in E-W Direction

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1

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Normalized Modal Displacement

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1st Mode2nd Mode3rd Mode

0 5 10 15 20 25 300

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Frequency (Hz)

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Second Mode Third

Mode

Modal Frequencies and Shapes in E-W Direction

Modal Frequencies and Shapes in N-S Direction

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1-1

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1st Mode2nd Mode3rd Mode

0 5 10 15 20 25 300

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Second Mode

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First mode in E-W

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SeismicRetrofitting

Demolition of Partition Walls

Change in Modal Frequencies by Time

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SeismicRetrofitting

07/20 11/04

Demolition ofPartition Walls

2.5Days (in 2010)07/20 11/04

First mode in N-S

Forced Vibration Test-1

Eccentricity(%)

Frequency(Hz)

Force(kN)

25 4.5 3.7050 4.5 7.3975 4.5 11.125 6.5 7.7150 6.5 15.475 6.5 23.1

Forced Vibration Test-2

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ecc: 7.5 %ecc: 25 %ecc: 50 %ecc: 75 %

Change in Modal Frequencies and Damping Ratios by Force

Ecc. (%) Frequency (Hz)Damping Ratio (%)

7.5 4.65 1.125 4.60 1.350 4.53 1.875 4.49 2.3

4 4.2 4.4 4.6 4.8 5 5.2 5.40

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Frequency (Hz)

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ecc: 25%ecc: 75%

4 4.1 4.2 4.3 4.4 4.5 4.6 4.7 4.8 4.9 50

0.5

Frequency (Hz)

Ecc. (%) Frequency (Hz)Damping Ratio (%)

25 4.88 1.175 4.81 2.3

Finite Element Model

Struts for infill walls

FEM Experimental

1. Modal Frequency 2.35 Hz 2.94 Hz



Seismic Vulnerability Assessment-1Methodology:

Obtain the distribution of max. story drifts obtained from the time-history

analysis using 10 input motions such as

PGA (g) MAGNITUTE NAME

0.55 6.1 BINGOL (03)0.81 7.2 Marmara - BOLU (November.99)0.27 6.2 CEYHAN (98)0.48 7.4 Marmara - DUZCE (Agust.99)0.27 6.2 CEYHAN (98)0.48 7.4 Marmara - DUZCE (Agust.99)0.47 6.1 ERZINCAN (92)0.18 6.7 VAN (11)

Obtain the exceedance probability using a limit state for the story drifts

Cases Considered:

W/O Infill Walls / %5 Damping

W Infill Walls / %5 Damping

W Infill Walls / %2 Damping

Seismic Vulnerability Assessment-2

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No Wall %5Wall %2Wall %5

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% Story Drift

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Seismic Vulnerability Assessment-3

Story DriftThreshold %1

Case Damping Ratio (%) Prob. Failure (%)

Without Wall 5 43

With Wall 5 25

With Wall 2 48With Wall 2 48

Story DriftThreshold %1.5

Case Damping Ratio (%) Prob. Failure (%)

No Wall 5 4

With Wall 5 4

With Wall 2 18

Conclusions

Due to infill walls the first structural frequency decreased by 10 %.

Modal damping ratio increases almost linearly with the applied force to structure.

Seismic vulnerability may change significantly if updated (identified) Seismic vulnerability may change significantly if updated (identified) parameters rather than non-updated (code suggested) parameters are used.

Vibration-based identification of actual modal parameters may be critical for the seismic vulnerability assessment of non-ductile buildings.

Acknowledgements

Assoc. Prof. Ertugrul TacirogluAsst. Prof. Kutay OrakcalAssoc. Prof. Hilmi Lus

MS StudentsEkin OzerTevfik TerziogluTevfik TerziogluFatih Kavarnali

Thank You

SERIES Committee

ambient vibration 1 slides

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