Structural health monitoring of intelligent infrastructure

10/25/2014
1
Structural health monitoring
of intelligent infrastructure
By
Saeed KIA
www.skia.ir
www.skia.ir
1
About me

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2
Saeed KIA is currently as PhD candidate in Civil Engineering at Amirkabir University of
Technology (Tehran Polytechnic) in Tehran, Iran.
Prior to this he was graduated as M.Sc. in Structural Engineering, M.Sc. in Construction
Engineering and Management from Amirkabir University of Technology (Tehran
Polytechnic), Master of Business Administration (MBA) from University of Tehran and
B.Sc. in Civil Engineering.
According to his professional experiences in structural design and analysis he research
in new fields such as Structural Health Monitoring, Construction Supply Chain, Heuristic
Optimization, Fluid Structures Interaction and Structural Design and Analysis. During
recent years he published two books and over 45 papers in national / international
conferences and journals.
According to his around over 8 years professional experience
and educational background, he is currently as associate member
of ASCE, ACI, PMI and ICE.
www.skia.ir
www.skia.ir
2
SHM

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• Deferred maintenance
– Design flaws
– Material failures
– Overloading
– Combination of all
Some Other Absolutes of Life (other than
Death and Taxes)Primary Causes of Engineering Failures
What is Structural Health Monitoring (SHM)
“The process of implementing a damage detection and
characterization strategy for engineering structures”
SHM Involves:
• Health monitoring
• Operational Evaluation
• Data Feature Extraction
• Statistical Models Development

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Monitoring Metrics
Measure:
• Acceleration
• Strain
• Climatic Conditions
• Curvature
• Displacements
• Load
• Tilt/Slope
• Scour
Identify
l Corrosion
l Cracking
l Strength
l Tension
l Location of
rebar/delaminations
Reliability of Biologically
Inspired (BI) Structures
SHM-Based Adaptive Bayesian
Assessment of Remaining Life
Prediction for BI Structures
Performance of BI Structures
under Random Loading
Effects of Structural Uncertainties
on Performance of BI Structures
Development of Minimum Life-Cycle
Cost Design for BI Structures
Simulation and Modeling of Stochastic
Loading and System Uncertainties
Optimal Maintenance Planning for
Inspection/Repair/Replacement of
BI Structures and Components
Damaged Region
Multi-level Structural Health
Monitoring Using
Advanced Sensing technology
Performance of Data Interpretation
Schemes under Uncertainties
Probabilistic
Structural
Analysis
Reliability Assessment
and
Life Prediction
Structural
Health
Monitoring

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SHM Applications
• Buildings (critical or even historical)
• Bridges
• Tunnels
• Wind Generators
>> Practically: Any critical structure
Structural Health Monitoring-SHM Applications
• Advanced health monitoring technologies
• Operational Evaluation
• Data Feature Extraction
• Statistical Models Development

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SHM Agenda
• What’s the talk about ?
• What’s structural health monitoring (SHM)?
• SHM techniques and their impact on sensor network design
• Architecture design for sensor network based SHM
• A prototype – implementation and deployment
• What next?
What’s the talk about?
• A programmable sensor network based
system for structural health monitoring
• What are the requirements of SHM
applications?
• How do we architect a sensor network
system to satisfy these requirements?
• A prototype and its performance

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What Is Structural Health Monitoring (SHM)?
• Structural integrity assessment for
buildings, bridges, offshore rigs, vehicles,
aerospace structures etc.
• Goals of SHM are:
– damage detection “is there damage?”
– damage localization “where is the damage?”
– damage quantification “how severe?”
– damage prognosis “future prediction”
Technological Solutions
– Wireless Sensors
• Accelerometers/Inclinometers etc
– Laser Scanning
– RFIDs
– Acoustic Emissions
– MEMS (Micro-Electro-Mechanical Systems)
– Increase of Computation capabilities
– Fiber technologies

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How Are Damages Caused?
• Extreme stress leading to fatigue in elements
– several freeway bridges today bear traffic far exceeding
tolerance levels they were originally designed to bear.
• Rusting and degradation of material properties
– leads to change in stress distribution and overloading
of certain elements more than others
• Continuous vibrations/cyclic stresses in the structure
– waves shaking offshore oil-rigs, gales shaking bridges.
• Catastrophes (earthquakes)
How Do Damages Evolve?
• Most damages start as tiny cracks caused by
metal fatigue (microns-mm).
• If unattended the cracks creep and grow in
size leading to deterioration of the material.
• If unchecked, it eventually results in an
unpredictable, sudden and catastrophic
failure.
• SHM techniques focus on detection and
localization of damages as early as possible.

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SHM Today
•Today SHM is carried out by
– collecting sensor data from several locations in the structure and
analyzing it on a high end platform
– periodic (bi-annual) human inspections (visual/using portable devices),
– expensive and dedicated data-acquisition systems (for structures where
monitoring is critical) .
• SHM suffers from
– human error and inaccessibility of locations within the structure
– expensive labor (for inspection), cabling and installation (for data-
acquisition systems)
– possibility of catastrophic failure between inspections
Feasibility of Local SHM Techniques
• They are expensive, require a lot of power and bulky
• Demand extremely dense deployments
• Local SHM techniques are not amenable to sensor network deployments
• So let us focus on global schemes henceforth

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What are the requirements of SHM schemes?
• High data rates – 100 sensor will generate a few Mbps of data
• Reliable Delivery – SHM algorithms do not tolerate sample losses
• Time Synchronization - Required by most schemes
• error in time-synchronization manifests as phase error in modes
• error ~ , the higher the modal frequency the more accuracy one needs
• For 1% error in a 20Hz mode, an accuracy of about 100
• Local computation – data acquisition system based solutions will not scale
tf2
s
Typical operation of an SHM system
• Sensors collect noise unless the structure is shaking!!!
• Ambient Schemes – rely on significant event (heavy wind, passing truck)
• Forced Schemes – rely on actuators (impact hammers)
• Structural Response lasts a few seconds!!!
• Sensors sleep unless an event occurs or the users requests actuators to test
• Sleep --- test/significant event ---- collect data and locally process ---
transmit to central location --- sleep (wake once a day/ once a few hrs)
• SHM systems will be Triggered Systems

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Architecture Design Decisions
• Two-level Hierarchy – A higher more endowed
layer is required to manage the aggregate data rates
generated by the motes.
• Isolate Application code from mote code – Mote
class devices provide a generic task interface but no
application specific code
• getSamples(startTime, noSamples, sampFreq, axis)
•getFFTSamples(startTime,noSamples,sampFreq,axis,fftSi
ze)
• actuateStructure(startTime,type, parameters)
• conveyed to motes as tasking packets by gateway-class
devices
Deployment
Seismic Test Structure
Scaled Building Model

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Damage Detection and Localization
on scaled model
• Building Details
• 48 inches high, 4 floors, 60 lbs
• Floors –1/2 x 12 x 18 aluminum plates
• steel 1/2 x 1/8 inch steel columns
• 5.5 lb/inch spring braces
• 4 actuators on the top floor
• 8 motes, 2/floor, dual axis, 200Hz, 2
starGates
• 4 Test Cases
• braces from floor 4 removed
• braces from floor 2 and 4 removed
www.skia.ir
3
Challenges

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ICCS
• Infrastructure is expected to provide:
– reliable service for long periods of time,
– following major technology changes,
– spanning several generations and experiencing dramatic
evolutions
• Develop Wireless Sensor Networks
– Reliable
– Energy aware
– Smart
Structural Monitoring Challenges
ICCS
Structural Monitoring Challenges
• Develop Design-to-service Solutions
– Efficient Monitoring
– DSP strategies
– Evaluation Criteria
– Knowledge bases
• Develop Smart Control Units
– Real-time Feedback
– Centralized (or not)

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ICCS
Technical Approach - Concept
ICCS
SHM EQ Concept
EarthquakeEvent
Sensors Wake-up
(unique IDs)
Events Recorded
and stored in BS
Sensors go
back to sleep

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ICCS
SHM in Countries
No Beneficiary name Short name Country
1 Institute of Communication and Computer Systems ICCS Greece
2 Interuniversitair Micro-Electronica Centrum VZW
Microsystems, Components and Packaging
IMEC Belgium
3 Stiching IMEC-NL IMEC-NL Netherlands
4 MEMSCAP S.A. MEMSCAP France
5 Concept to Volume BV (C2V) C2V Netherlands
6 University of Trento-Department of Mechanical and structural
Engineering
UNITN Italy
7 TECNIC S.p.A. TECNIC Italy
8 D.Bairaktaris and Associates Ltd. DBA Greece
9 RISA Sicherheitsanalysen GmbH RISA Germany
10 Advanced Microwave Systems Ltd. AMS Greece
11 Acropole Charagionis S.A. ACH Greece
12 SITEX 45 SRL SITEX Romania
www.skia.ir
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Case
Studies

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San Jacinto Monument
Built 1936
La Porte, Texas
1981 Study
1. Monument suspected to have
tilt: Measured tilt to be within
construction tolerances
2. Excessive settlement
suspected: Monument
supported by a monolithic mat
foundation. Top of mat built
exposed.
3. Discovered that a settlement
monitoring program was set up
during construction in 1936
4. Searched archives for data:
Found documents in the
archives of the Houston Public
Library
5. A Geotechnical engineer was
retained to review past data
San Jacinto Monument Mat Foundation SHM
From City of Houston Public Library Archives

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McClelland Engineers Soundings
Winter 1984
McClelland Engineers
Soundings Winter 1984

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1. Modifications to an existing structure,
2. Monitoring of structures affected by external
factors,
3. Monitoring during demolition,
4. Structures subject to long-term movement or
degradation of materials,
5. Feedback loop to improve future design based on
experience,
Objectives of Structural Health Monitoring: Farrar and Worden (2007)
6. Fatigue assessment,
7. Novel systems of construction,
8. Assessment of post-earthquake structural
integrity, and
9. Growth in maintenance needs.
Objectives of Structural Health Monitoring

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www.skia.ir
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SHM
1. Strain gages,
2. Inclinometers,
3. Displacement transducers,
4. Accelerometers,
5. Temperature gages,
6. Pressure transducers,
7. Acoustic sensors,
8. Piezometers, and
9. Laser optical devices
Instrumentation used for SHM

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• Most of these sensors can be wirelessly
connected.
• Technology using solar energy is very common in
instrumentation.
• Latest technology even has self powered systems,
i.e. no external power required.
Instrumentation used for SHM
www.skia.ir
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Case 01

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Health Monitoring of a Stadium Truss During Erection
• Segmented Erection.
• Monitor strains and stresses at various stages of
erection.
• Verification of predicted behavior was needed

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Key Challenges
• Non-interference with the construction
schedule.
• No wires were allowed to run from one
segment to the other.
• No main power supply.
• No drilling or welding on to the frame.
• Each segment needed to be prepared and
instrumented in a narrow 2 day interval.
• No lift access after erection.
Instruments
• MicroStrain V-Link
– 4 Strain gauges could be attached
to the device.
– Fully ruggedized for exterior
applications.
– One laptop with data querying
software was sufficient to access
all boxes.
– Low duty cycle can give up to 1
year of battery life.

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Over 9 Months
Over 9 Months

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www.skia.ir
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Case 02
Health Monitoring of a Data Center

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o Reinforced concrete high-rise building.
o Raised access floors.
o Owner wanted to build a fitness center next to
the data center.
Key Challenges
• Needed to prevent undesirable vibrations in the data
center.
• Quantify sensitivities of many high-performance
computing systems.
• Needed to inform the contractor immediately upon
discovery of an issue.
• Alarm system to alert Walter P Moore and the
contractor.

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Instruments
• Pre-construction Testing.
– National Instruments dynamic
data acquisition system.
– PCB G scale accelerometers.
• Construction and Operations
Time Monitoring
– Instantel Blastmate device.

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Vibrations Measured in the Computer Room
10
100
1,000
10,000
100,000
1,000,000
10,000,000
0 10 20 30 40 50 60 70 80
Frequency
PPV(in/sec)
Threshold For Computers and 100x Microscopes
HP
Sun
Dell PowerEdge
SGI Orign and Altix
SGI Origin 200 and 300
Scalar i2000 Tape Backup
Most Severe Events (30)
Shock tolerance threshold
Table 1. Marathon Oil Tower Vibration Testing Summary For November -2006
Date Day Number of Recorded Events
Above 0.02 in/s Above 0.1 in/s
11/1/2006 WEDNESDAY 135 0
11/2/2006 THURSDAY 106 0
11/3/2006 FRIDAY 32 0
11/4/2006 SATURDAY 50 0
11/5/2006 SUNDAY 0 0
11/6/2006 MONDAY 58 1
11/7/2006 TUESDAY 31 0
11/8/2006 WEDNESDAY 135 0
11/9/2006 THURSDAY 82 0
11/10/2006 FRIDAY 25 0
11/11/2006 SATURDAY 48 1
11/12/2006 SUNDAY 10 0
11/13/2006 MONDAY 54 0
11/14/2006 TUESDAY 220 3
11/15/2006 WEDNESDAY 68 1
11/16/2006 THURSDAY 155 1
11/17/2006 FRIDAY 11 0
11/18/2006 SATURDAY 86 0
11/19/2006 SUNDAY 7 0
11/20/2006 MONDAY 0 0
11/21/2006 TUESDAY 0 0
11/22/2006 WEDNESDAY 2 0
11/23/2006 THURSDAY 6 0
11/24/2006 FRIDAY 8 0
11/25/2006 SATURDAY 8 0
11/26/2006 SUNDAY 7 0
11/27/2006 MONDAY 264 0
11/28/2006 TUESDAY 55 0
11/29/2006 WEDNESDAY 35 0
11/30/2006 THURSDAY 0 0
www.skia.ir
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Case 03

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Health Monitoring of a Parking Garage Structure
• Precast Concrete parking garage with precast
façade.
• Had a history of structural retrofits.
• Noticed signs of structural tilt (1999).
• Owner wanted assurance that there is no
foundation settlement occurring.

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Key Challenges
• Selection of monitoring location.
• Selection of types of measurements.
• Need to operate during power outages.
• Sensor installation.
• Data logger installation.
• Remote communication setup.
• Alarm system to alert engineer and the
client.
Instruments
• Campbell Scientific
CR10X logger with DC
backup.
• Inclinometers with
temperature sensors.
• Anemometer.
• Rain gauge.

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§Sensors on 4th and 7th levels.
Installation
Health Monitoring in Progress During Hurricane Ike

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www.skia.ir
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Case 04
Health Monitoring of a Bridge Essential to
Business Operations

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Business Operations
§Precast concrete bridge.
§Business operations will be halted if bridge fails.
§No information was available to rate the capacity.
§No analytical work could be done without
exhaustive NDE
§Owner wanted to transport heavy construction
material and equipment over the bridge for next 3
years.
§SHM was suggested to monitor the bridge during
the heaviest loading phase for 1 year.
Key Challenges
• Installation of inclinometers under girders.
• Access was difficult.
• Night time installation was preferred.
• Installation has to be stopped when a train passed
by under the bridge.
• The whole system needed to be run with solar
power.
• Remote communication setup.
• Alarm system to alert the engineer and the client.
Business Operations

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Instruments
• Campbell Scientific
CR1000 logger with solar
power.
• Tilt beams with
temperature sensors.
• Cellular TCP/IP modem
facilitates accessing data
over the internet
Business Operations
Installation
Business Operations

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www.skia.ir
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Case 04
Detection of Sudden Damage
ASCE Benchmark Study for Health Monitoring

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Natural frequencies
0
20
40
60
80
100
120
140
160
1 2 3 4 5 6 7 8
vibration mode
frequency(rad/s)
Health structure
Damaged structure
50% stiffness loss
of two braces on
the first floor at
t = 2.5s
Less that 5%
change in the
natural freqs.
due to the
local damage
Sudden damage detected
on the first floor at t =
2.5s
Robustness to measurement
noise (2%RMS of response)
Experimental Validation:
Shaking Table Test of a Two-Story Full-Size Wooden Frame

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Application
Monitoring Progressive Stiffness Degradation
M
1
K1
C1 M
2
K2
C2 M
3
K3
C3
Time
(sec)
Instantaneous Natural frequency (Hz)
1st mode 2nd mode 3rd mode
CWT Modal
analysis
CWT Modal
analysis
CWT Modal
analysis
5 1.293
0
1.2932 3.6181 3.6234 5.2357 5.2360
15 1.261
4
1.2619 3.5918 3.5956 5.0542 5.0586
25 1.223
4
1.2230 3.5553 3.5589 4.8774 4.8824
3DOF Model with a damageable Spring
Comparison with Analytical Results
Wavelet ridges
Instantaneous
Frequencies
Instantaneous modeshapes
www.skia.ir
11
Conclusio
n

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SHM
Data Acquisition
Data Collection
Processing & Feedback

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Contact me:
www.skia.ir
ADDRESS:
Amirkabir University of Technology,
Hafez Street,
Tehran - Iran
PHONE:
+98 912 71 36 971
EMAIL:
skia@aut.ac.ir
THANK YOUSaeed KIA
Email: skia@aut.ac.ir
Mobile: (+98) 912 71 36 971
www.skia.ir

10/25/2014
42
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