An Improved Modal Strain Energy Method for Damage Queensland University of Technology CRICOS No. 00213J

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  • Queensland University of Technology

    CRICOS No. 00213J

    An Improved Modal Strain Energy

    Method for Damage Assessment

    Presented By:

    Buddhi L. Wahalathantri D. P. Thambirathnam

    T.H.T. Chan

    S. Fawzia

  • CRICOS No. 00213Ja university for the worldreal R

    Presentation Outline

    • Introduction

    • Theory: Strain Energy based Damage Indices

    • Problem Identification

    • Improved SE Method

    • Results

    • Conclusions & Future Work

  • CRICOS No. 00213Ja university for the worldreal R

    Introduction

    • Damage Detection

    – Vibration Based Damage Identification Techniques

    • Modal Strain Energy Method

    • SE Method

    – Damage Identification & Localization [Ref 6]

    – Require first few modes to be measured and used

    – False Alarms

    – Not detect some damage locations (multiple damage)

    – Improved SE Method

  • CRICOS No. 00213Ja university for the worldreal R

    Theory: SE of a Euler Bernoulli Beam

    • Strain energy of a Euler-Bernoulli beam: Mode

    ‘i’, Element ‘j’:

    1 2 j N

    Node 1 2 3 j j+1 N N+1

    Distance 0 aj aj+1 L

  • CRICOS No. 00213Ja university for the worldreal R

    SE based Damage Indices

    • β1: Cornwell et al [Ref. 9]

    • β2: Park et al [Ref. 10]

  • CRICOS No. 00213Ja university for the worldreal R

    SE based Damage Indices

    • β3: Li et al [Ref. 11] & Shih et al [Ref 12]

  • CRICOS No. 00213Ja university for the worldreal R

    Problem Identification

    • False Alarms

    – At Nodal Points

    • Indicates undamaged locations as damage

    – Missing information

    • Not detecting some damage locations

    – Small damage severities

    – Multiple damage locations

    • Need higher mode addition

  • CRICOS No. 00213Ja university for the worldreal R

    Improved SE Method

    • New DI

    – Minimise false alarms

    – Improve damage detection

    – Minimise number of modes

    • Improved DI: β4

  • CRICOS No. 00213Ja university for the worldreal R

    Improved SE Method

    • Modification Function: MFij – Using Mode shape curvature values

    – Simply supported beam

  • CRICOS No. 00213Ja university for the worldreal R

    Present Study Summarizes……..

    • Simply Supported Beam

    – Single Damage

    • 28 Damage Cases

    – 7 Damage Locations: L/8, 9L/56, 3L/16, L/4, 3L/8, 7L/16, L/2

    – 4 Damage Severities: 10%, 20%, 30%, 40%

    – Multiple Damage Cases (Two Damages):

    • 32 Damage Cases

    – By varying both Damage Locations and Severities

    • Multiple Spans (Two Spans) • 30 Damage Cases

  • CRICOS No. 00213Ja university for the worldreal R

    Method

    • Data Analysis

    – Data Analysis Software

    • MATLAB Environment

    • By Developing a Programme

    • With GUI

    • Supports 3 Types of Input (to date) data

    – Experiment Results (extracted mode shape values)

    – FEM Results: ABAQUS & SAP 2000

    • Simultaneous Analysis with different number of modes

    • Ability to address Forward and Inverse Problem

  • CRICOS No. 00213Ja university for the worldreal R

    Results

    • Simply Supported Beam

    – Single Damage with different;

    • Damage Location (DL)

    • Damage Severity (DS)

    – Multiple Damages

    • Case 1: DL1 = L/4, DS1 = 40%, DL2 = L/2, DS2 = 40%

    • Case 2: DL1 = L/4, DS1 = 10%, DL2 = L/2, DS2 = 40%

    • Two Span Beam

    – Damage locations: Mid Spans

  • CRICOS No. 00213Ja university for the worldreal R

    Results: Comparison of DIs

    • β1 vs. β4 – Simply supported beam [Ref. 12]

    – DL: L/2

    0

    2.5

    5

    7.5

    10

    12.5

    15

    0 0.7 1.4 2.1 2.8

    β 1

    Distance: x (m)

    β1:Mode 3

    -2

    0

    2

    4

    6

    8

    10

    0 0.7 1.4 2.1 2.8

    β 4

    Distance: x (m)

    β4:Mode 3

  • CRICOS No. 00213Ja university for the worldreal R

    Results: Comparison of DIs

    • β2 vs. β4 – Simply Supported Beam

    – DL1 = L/4, DS1 = 40%, DL2 = L/2, DS2 = 40%

    -2

    0

    2

    4

    6

    8

    10

    12

    0 0.7 1.4 2.1 2.8

    β 4

    Distance: x (m)

    β4:Mode 2

    0.98

    1

    1.02

    1.04

    1.06

    1.08

    1.1

    0 0.7 1.4 2.1 2.8

    β 2

    Distance: x (m)

    β2:Mode 2

  • CRICOS No. 00213Ja university for the worldreal R

    Results: Comparison of DIs

    • β3 vs. β4 – Simply Supported Beam

    – DL1 = L/4, DS1 = 10%, DL2 = L/2, DS2 = 40%

    0.98

    1

    1.02

    1.04

    1.06

    1.08

    1.1

    1.12

    1.14

    0 0.7 1.4 2.1 2.8

    β 3

    Distance: x (m)

    β3:Modes 1-5

    -1

    0

    1

    2

    3

    4

    5

    6

    0 0.7 1.4 2.1 2.8

    β 4

    Distance: x (m)

    β4:Modes 1-5

  • CRICOS No. 00213Ja university for the worldreal R

    Damage Index: β4

    • Two Span Beam

    – Damage at middle of each spans

    -0.4

    -0.2

    0

    0.2

    0.4

    0.6

    0.8

    1

    1.2

    1.4

    0 1.4 2.8 4.2 5.6

    β 4

    Distance: x (m)

    β4:Mode 1

    -0.2

    0

    0.2

    0.4

    0.6

    0.8

    1

    0 1.4 2.8 4.2 5.6

    β 4

    Distance: x (m)

    β4:Modes 1, 2 & 3

  • CRICOS No. 00213Ja university for the worldreal R

    Damage Index: β4

    • Potential to Damage Quantification

    0

    2

    4

    6

    8

    10

    0 0.35 0.7 1.05 1.4

    β 4

    Distance: x (m)

    β4:Mode 1

    DS=10%

    DS=20%

    DS=30%

    DS=40%

  • CRICOS No. 00213Ja university for the worldreal R

    Damage Index: β4

    • Potential to Damage Quantification

    0

    2

    4

    6

    8

    10

    0 5 10 15 20 25 30 35 40 45

    β 4

    Damage Severity (DS%)

    β4:Mode 1

    x=0.4375 m

    x=0.525 m

    x=0.7 m

    x=1.4 m

  • CRICOS No. 00213Ja university for the worldreal R

    Conclusions

    • Proposed Damage Index;

    – Minimise False Alarms

    – Improved damage detection

    • Compared to other SE based methods

    – Minimise Number of Modes

    – Potential to Damage Quantification

  • CRICOS No. 00213Ja university for the worldreal R

    Further Studies

    • Improved Results with Noisy Data

    – Up to 5% Noise

    – Reinforced Concrete Beams

    – Load Induced Damage Cases

    • Need studies on;

    – Damage quantification

  • Queensland University of Technology

    CRICOS No. 00213J

    Thank You

    Email: b.wahalathantri@qut.edu.au

    Mobile: (34) 6 0314 3873

    (61) 4 3064 9620

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