research summary - university of mississippi
TRANSCRIPT
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Research Summary
Dr. Elizabeth K. Ervin Assistant Professor
Department of Civil Engineering
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Background
Ph.D., Carnegie Mellon University, Mechanical Engineering. M.S., Vanderbilt University, Civil Engineering; B.S., Tennessee
Technological University, Civil Engineering. Joined as Assistant Professor, Department of Civil Engineering,
in August 2006. September 2001 to March 2006 Bechtel Bettis, Inc. Bettis Atomic Power Laboratory, a Department of Energy/U.S.
Navy Contractor, Pittsburgh, Pennsylvania. Reactor Technology Activity, Reactor Engineering Division,
Structural Methods Analysis and Design, Shock and Vibration; Acoustic Design & Development, Noise, Vibration, & Shock
Also, Summer Research Program, Air Force Research Laboratories
Air Vehicles Directorate Structures Division, Structural Design & Development Branch (ARFL/VASD), WPAFB.
Funding from NSF, DOD, ORNL, NRC.
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“Extreme” Effects
Contact
Shock
Blast
Seismic
Other “abnormal” events that cause load amplification
Aging
Fatigue
Fracture
Other “unexpected” outcomes from normal or abnormal loading
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Triggering Causes of Infrastructure Failure
External Events, Natural Hazards, Manmade Events
Seismic
Fire Overload
Weidlinger
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Modes of Failure Time Scale
Ductile
Brittle
Progressive
Weidlinger
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“Health”
How can a massive structure be instrumented to show damage using only measurements?
What parameter will best indicate damage?
What is the uncertainty in this indicator?
How can this indicator show cumulative damage?
When does a structure become too damaged and need reinforcement or demolition?
Will the implemented method be cost beneficial?
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Rytter’s Health Hierarchy:
Detection
Location
Severity
Prognosis
Two main approaches:
Inverse problem
Pattern Recognition
Data acquisition
Pre-processing
Feature extraction
Classification
Decision
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0
5000
10000
15000
2 3 4 5 6 7 8 9 10
Am
pli
tud
e (g
/V)
Frequency (Hz)
Undamaged
Damage State 1
Damage State 2
34.60%
27.75%
3.78 Hz 3.78 Hz
5.78 Hz
3.78 Hz 3.78 Hz
5.78 Hz
8 Hz
Incrementally Damaged Tower: Experimental Series 1
Increasing Damage by Removing Bracing
Results
• Decreasing frequency
• Increasing displacement
Consistent with decreasing stiffness
1 2
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Incrementally Damaged Building: Experimental Series 2
Increasing Damage by Removing Bracing
10 Damage Cases, 4 Reinforced Cases; Both modal tap tests and shake tests.
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Schematic of Building Experiment
Xcitex ProAnalyst Post-Processing Edge Detection
for Displacement
Tri-axial
Accelerometer
Calibration
Table
Motion
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0 10 20 30 40 50 60 70 80 90 100
Obtained Modal Peaks from STAR Modal using tap test data
Experimental Series 2 Results
Frequency (Hz)
Fre
qu
ency
Res
po
nse
Am
pli
tud
e
Incr
easi
ng
Dam
age
by R
emo
vin
g B
raci
ng
Splitting
Frequencies
Decreasing
Frequencies
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Spatial Scale of Failure
Nano-scale
Meter-scale
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SDOF Model of Cracked Beam
Parameter α ‘represents’ depth
of crack
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Cracked Beam FRF Response (Worden)
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Numerical Model
Fixed-Free Beam
Kt1 = k1= ∞
Kt2 = k2= 0
gap
Experimental Study
Shake
Table
High
Speed
Camera
Motion
Impact Mechanics and
Model Verification
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Machinery Example
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Other Areas of Interest
Various Modes of Excitation, including Shock Loading
Blast with Fluid Effects
Impact Response of Beam Structures
Contact Mechanics - Other than hybrid linear mapping
Active and Passive Vibration Control
Coupled Motions: Axial, Torsional, Transverse Vibration
Acoustics and flow-induced vibration
Composite material modeling
Experimental verification
Model reduction methods
Nuclear Engineering education
Outreach
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More Information
http://home.olemiss.edu/~eke/
Homepage, Labpage, Nukepage