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Transcript of Copy of Hemant Presentation 6 Oct
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Structural Health Monitoring and Damage
Detection of Structures
Presented by Guided by
Hemant Kumar Vinayak Dr. S.K. Thakkar
Dr. Ashok Kumar
Dr. Pankaj Agrawal
Department of Earthquake Engineering
Indian Institute of Technology
Roorkee, UA
Ph.D. Research Proposal
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Presentation Overview
Introduction
Objectives Methodology involved
Experimental setup details
Plan of work
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Structural Health Monitoring (Definition)
Focuses on techniques of :
Identifying the existence of damageIdentifying the location of damage
Estimating the magnitude of damage
Introduction (Contd..)
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Structural Health Monitoring (Application)
Civil Infrastructure (Bridges, Highway, Buildings etc.)
Air Craft and Missile Structures
Space Structures
Land/ Marines Structures
Introduction
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Project Proposal (Contd..)
Objectives
Present an overview of Damage Detection and Structural
Health Monitoring methods for buildings. Establish a correlation between damage in the model with
its known dynamic characteristics.
Comparative study of damage detection techniques for
building structures Develop methodology of damage detection and health
status in pre and post earthquake scenario using Non-
destructive Evaluation (NDE) techniques
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Literature review
1. Literature review-
Identification of various methods
Selection of experimental procedure
Identifying the set of controlling parameters that are
need to be computed through experimentation
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Methodology Involved (Contd..)
Changes in basic modal
properties
Dynamically measured
flexibility
Updating structural
model parameters
Frequency changes Comparison of flexibility
changes
Optimal Matrix update
methods
Mode shape changes Unity check method Sensitivity based
update methods
Mode shape curvature/
Strain mode shapechanges
Stiffness error matrix
method
Eigen structure
Assignment methods
Changes in modal energy,
Kinetic energy
Effect of residual
flexibility
Hybrid matrix update
methods
Changes in measured
stiffness matrix
Vibration based damage detection methods (Review by Doebling)
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Structural Health Monitoring (Method for
Current Research)
Changes in basic model properties at each level of damage
during the experiment:
frequency
Mode shapes,
Modal strain energy,
Methodology Involved (Contd..)
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Methodology Involved (Contd..)
Determine
Stiffness from displacement versus load graph
Natural frequency, mode shape and damping ratio from freevibration test. Damping from logarithmic decrement
Natural frequency, mode shape and damping ratio from
forced vibration test. Damping ratio will be determined from
half power band width methodMode shapes - The data acquired will coupled with the model
generated in ARTeMIS software
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Methodology involved (Contd..)
Structural Health Monitoring (Method for
Current Research, Contd..)
Level of
damage in %
Hysteresis
Loop Load vs.Deflection
curve
Mode shapes Hysteresis
damping
Natural
frequency
Negligible
Light
Moderate
Heavy
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Damage indices Methodology (Contd..)
Most traditional
indicator
Displacement ductility
Koh Integrity index
DisPasquale E and
Cakmak A.S.
1990
Maximum deformation
Skaerbaek P.S.
1996
Drift ratio
Park R 1996 ;
Bachmann H 1996
Stiffness ratio
ui
di
i S
S
S !
yield
d Q
Q Q
max!
H Di max Q
!
f irstyield
failureM Di
U/!
max,
,1
T i
initial T i Di !
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Methodology Involved (Contd..)
Nagar, A ;1995,
Bernal D; 1992,
Ghobarah, A;1999
Flexural damage rotation
SARCOF Damage Indicator
Kraetzig W et al
2000
Softening index
max
0
K
K Di !
0
5.0)(1
EI
t EI Di
!
o
d
E
E Di ! 1
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Methodology Involved (Contd..)
Modal assurance criteria
Normalised area
difference
Relative difference
§§
§!
jun j
jd n j
j
un jd n j
MAC 22
2
)()(
])()([
J J
J J
dx N A D ud ´ ! J J
un j
un jd n jn j R D
)()()(
J J J !
Ewins 1984 Salawu and Williams 1994
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Model 1 A concrete cantilever column subject to lateral load
Experimental Setup Details
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Model 2 A single story plane frame subject to lateral load
Experimental Setup Details
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Model 3
One bay subject to uniaxial load
Experimental Setup Details (Contd..)
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Model 4
Experimental Setup Details (Contd..)
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Plan of Work
Jan 2004 to Oct 2004 i) Course work
ii) Comprehensive exam
iii) Literature review
Oct 2004 to Dec 2005 i) Fabrication of Models
ii) Testing of Models
Jan 2006 to Jun 2006 i) Analysis and Presentation of result
July 2006 to Dec 2006 i) Writing of PhD Thesis
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Publications
Thank you
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Future central monitoring station
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Methodology Involved (Contd..)
Changes in basic modal properties
Frequency changes (Review by O.S. Salawu)
Loss of stiffness - When measured natural frequencies are substantially lower
than expected
Damage Causes - Support failure, crack propagation, shear failure and overload
causing internal damage
Degree of reduction - Dependent on the position of the defect relative to modeshape for a particular mode of vibration
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Methodology Involved (Contd..)
Changes in basic modal properties
Equation of motion
[ [k] - [2[M] ]{J } = {0}
[ (k+Hk) - ([2 + H [2 ) [M] ]{J + HJ } = {0}
Stiffness depends upon -Property of materials - Modulus of Elasticity E, Density V
Dimension of element - b, d, L
Damage induction in the structure
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Mode shapes of undamaged and damaged steel frame infilled with
unstiffened thin steel plate shear panels - Prion and Rezai 1996
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Methodology Involved (Contd..)
Modal strain energy change MSEC
i j
i ji jd
i jMS E
MS E MS E
MS ECR
!
Undamaged modal strain energy MSEij = JiTk j Ji
Damaged modal strain energy MSEdij = Jd
iTk j J
di
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Methodology Involved (Contd..)
Changes in basic modal properties
Mode shape changes
West 1984 - Changes in Modal Assurance Criterion to localize structural damage
Fox 1992 - Graphical comparison of relative changes in mode shapes
Cobb and Liebst 1997 - Prioritizing sensor location based on eigenvector
sensitivity analysis
Skjaeraek 1996 - optimal sensor location for damage detection based on
changes in mode shapes using substructure iteration method
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Methodology Involved (Contd..)
Changes in basic modal properties
Mode shape curvature/ strain mode shape changes
Utilizes relationship between curvature and bending strain for beams plates
and shells
Pandey et al 1991 - Changes in mode shape curvature can be a good indicator
for Fem beam structure.
Chance et al. 1994 - Numerically calculating curvature from mode shapes
resulted in unacceptable errors. Measured strains improved the resultdramatically.
Chen and Swamidas (1994), Dong et al (1994), Kondo and Hamamoto (1994),
Nwosu et al (1995) and Yao and Change (1995)
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Methodology Involved (Contd..)
Dynamically measured flexibility
Comparison of flexibility changes
Utilizes relationship between curvature and bending strain for beams plates
and shells
Pandey et al 1991 - Changes in mode shape curvature can be a good indicator
for Fem beam structure.
Chance et al. 1994 - Numerically calculating curvature from mode shapes
resulted in unacceptable errors. Measured strains improved the resultdramatically.
Chen and Swamidas (1994), Dong et al (1994), Kondo and Hamamoto (1994),
Nwosu et al (1995) and Yao and Change (1995)
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Methodology Involved (Contd..)
Dynamically measured flexibility
Unit check method
An error matrix is defined which measures the degree to which
pseudoinverse relationship between the dynamically measured flexibility
matrix and structural stiffness matrix is satisfied
Lim 1990 - Proposes for locating modeling error and uses the location of the
entry with maximum magnitude in each column to determine the error location.
Lim 1991 - Defines a least square problem for the elemental stiffness changes
consistent with unity check error in potentially damaged members
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Methodology Involved (Contd..)
Dynamically measured flexibility
Effect of Residual Flexibility
Represents contribution to the flexibility matrix from modes outside
measured bandwidth so that exact flexibility matrix can be related to
measured modes.
Doebling et al. 1996 - Technique to estimate unmeasured partition of residual
flexibility matrix .
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Methodology Involved (Contd..)
Dynamically measured flexibility
Changes in Measured Stiffness matrix
Pseudoinverse of dynamically measured flexibility matrix.
Salawu and Williams 1993 - Used direct comparison of measured parameter to
estimate damage .
Peterson et al. 1993 - Proposed a method to use measure stiffness and mass
matrices to locate damage
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Methodology Involved (Contd..)
Updating structural model parameters
Optimal matrix update methods
Pseudoinverse of dynamically measured flexibility matrix.
Salawu and Williams 1993 - Used direct comparison of measured parameter to
estimate damage .
Peterson et al. 1993 - Proposed a method to use measure stiffness and mass
matrices to locate damage