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- Front Matter: Volume 7983
- Plenary Session
- Laser, Ultrasound, Acoustic Emission NDE I
- NDE in Civil Infrastructure I
- Laser, Ultrasound, Acoustic Emission NDE II
- NDE in Civil Infrastructure II
- NASA-based NDE/SHM Activities
- NDE in Composites
- PNNL-based NDE in Homeland Security Applications
- NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems I
- Fiber Optics Sensors Technologies
- NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems II
- Radar/Lidar NDE Technologies
- NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems III
- Thermal, Infrared, and Radiographic NDE Technologies
- NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems III
- NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems IV
- Wireless Sensor Network and Energy Harvesting
- Vibration-Based NDE Technologies
- Smart Materials Sensing Technologies
- Poster Session
Front Matter: Volume 7983
Front Matter: Volume 7983
Show abstract
This PDF file contains the front matter associated with SPIE Proceedings Volume 7983, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
Plenary Session
The upcoming revolution in ultrasonic guided waves
Joseph L. Rose
Show abstract
This paper will include discussions on fundamental principles and market forces associated with the
upcoming revolution in ultrasonic guided waves. A literature survey is also outlined covering some selected
major developments this past decade. A few applications in pipe, rail, bonding and composites, imaging and
tomography, ultrasonic vibration, de-icing, structural health monitoring, gas entrapment, and non-linear
methods are treated to provide an idea of where we are heading with ultrasonic guided waves.
Laser, Ultrasound, Acoustic Emission NDE I
Continuous acoustic emission monitoring of reinforced concrete under accelerated corrosion
Show abstract
The development of techniques capable of evaluating deterioration of reinforced concrete (RC) structures is instrumental
to the advancement of techniques for the structural health monitoring (SHM) and service life estimate for constructed
facilities. One of the main causes leading to degradation of RC is the corrosion of the steel reinforcement. This process
can be modeled phenomenologically, while laboratory tests aimed at studying durability responses are typically
accelerated in order to provide useful results within a realistic period of time. To assess the condition of damage in RC, a
number of nondestructive methods have been recently studied. Acoustic emission (AE) is emerging as a nondestructive
tool to detect the onset and progression of deterioration mechanisms. In this paper, the development of accelerated
corrosion and continuous AE monitoring test set-up for RC specimens are presented. Relevant information are provided
with regard to the characteristics of the corrosion circuit, continuous measurement and acquisition of corrosion potential,
selection of AE sensors and AE parameter setting. The effectiveness of the setup in detecting and characterizing the
initiation and progression of the corrosion phenomenon is discussed on the basis of preliminary results from small-scale,
pre-cracked RC specimens, which are representative of areas near the clear cover in typical RC bridge members.
Early state damage detection of aluminum 7075-T6 plate based on acoustic emission
Show abstract
Aluminum alloy 7075-T6 is a commonly used material in aircraft industry. A crack usually initiates at the
edge of a fastener hole, and it can affect the maintenance schedule and reduce the life of an aircraft structure
significantly. The fatigue property of the material has been researched widely to develop methods and models
for predicting fatigue crack growth under random loading. From the point of damage tolerance design, the
inspection technique of a crack for an aircraft structure is very important because it can be used to determine
the inspection period of the aircraft structure. The acoustic emission (AE) technique is a nondestructive
testing (NDT) method that is able to monitor damage initiation and progression in real time. Understanding
the early stage of AE signature due to the damage progression using small scale laboratory samples requires
non-traditional data analysis approaches. In this study, 1mm thick Al-7075-T6 plates were tested under
monotonic and fatigue loading. The initiation of damage progression using AE data was identified based on
improved linear location algorithm and the result was verified using elasto-plastic finite element model. The
improved location algorithm integrates dispersive characteristics of flexural waves and threshold independent
approach to pick up the wave arrival time. In this paper, AE results in comparison with FE model under
monotonic and fatigue loading will be presented. The comparison of traditional and improved location
approaches will be shown. The approach for implementing the laboratory scale results in the large scale field
testing will be discussed.
Environmentally induced acoustic emission from reinforced concrete
Show abstract
A system is being developed to monitor in-service deterioration of reinforced concrete (RC) in highway bridges. The
system includes the monitoring of acoustic emission (AE). To develop a preliminary understanding of AE source
mechanisms and their causes while also getting closer to the challenges of separating relevant AE from noise, a 6ft long
RC test article was monitored in the outdoors environment of a New Jersey summer. There were indications of daily
swings in the AE rate, coinciding with the daily swings in temperature. However this correlation was not consistent or
reproducible. As the monitoring was extended into the winter and the test site was buried in snow, the AE rate dropped
drastically. It was concluded that temperature changes were instrumental in stimulating AE from this damaged concrete.
Implications for the formulation of AE evaluation criteria are discussed. Also, the summer swings provoked
consideration of the underlying stress field, the fractal nature of the heterogeneous material and the stochastic AE
phenomenon. An analysis of calm time distributions yielded results similar to those found by Abe and Suzuki for
earthquake time distributions. Analysis of this kind may help to differentiate relevant AE from some kinds of noise.
Micromechanics models and innovative sensor technologies to evaluate internal-frost damage of concrete
Show abstract
Internal-frost damage is one of the major problems affecting the durability of concrete in cold regions. This paper
presents micromechanics models and innovative sensor technologies to study the fundamental mechanisms of frost
damage in concrete. The crystallization pressure due to ice nucleation with capillary pores is the primary cause of
internal-frost damage of concrete. The crystallization pressure of a cylinder pore was formulated using interface energy
balance with thermodynamics equations. The obtained crystallization pressure on the pore wall was input for the fracture
simulation with the developed Extended Finite Element Model (XFEM). The XFEM fracture simulation on a
homogeneous beam sample with a vertical cylinder pore leads to a straight line. The XFEM simulation was also
conducted on the generated digital sample. The simulation results were favorable compared with the middle-notched
single edge beam bending specimen due to the open-mode fracture behavior in both cases. An innovative Time-Domain
Reflectometry (TDR) sensor was developed to nondestructively monitor the freezing process. The experimental data
shows that the TDR sensor signals can detect the freezing degree, an important input parameter to micromechanics
models. These studies indicate that the developed micromechanics models and TDR sensor techniques can be used by
the practitioners to evaluate internal-frost damage of concrete. Future work will incorporate the TDR sensor
measurements into micromechanics models to real-time predict the internal-frost damage process in concrete specimens.
The predicted freeze-thaw damage process will be verified with acoustic emission detection.
NDE in Civil Infrastructure I
Study of concrete drilling for automated non-destructive evaluation and rehabilitation system for bridge decks
Show abstract
Robotic drilling is the basic process for the non-destructive rehabilitation (NDR) system in the Automated Non-destructive
Evaluation and Rehabilitation System (ANDERS) for bridge decks. In this paper, we present a study
and testing of a concrete drilling process that is used for robotic drilling process for bridge decks repair. We first
review the ANDERS and NDR design. Then we present the experimental setup for the drilling process study.
A set of testing experiments are performed considering drilling process parameters such as drill bit size, drill
rotating speed, drill thrust force and types of concrete composites. Based on the experiments and analysis, we
identify and find that the optimal set of drilling process parameters for the ANDERS application is 1/4-inch bit
size, drill rotational speed of 1500 rpm and thrust force around 35 lbs. We also demonstrate that the monitoring
of drill feeding displacement and thrust force cannot be used to detect and identify the cracks in bridge decks.
Nanoscale materials for non-destructive repair of transportation infrastructures
Show abstract
Results related to the development of an inorganic matrix that is suitable for filling narrow cracks and thin delaminations
on bridge decks are presented in this paper. Almost all the repair materials currently available for these types of repairs
are organic polymer based matrices. These matrices create a discontinuity in the modulus of elasticity and water
permeability. These discontinuities result in the failure of repairs within about five years. The matrix used in the current
investigation has a modulus of elasticity and permeability characteristics that are similar to the concrete used in the
bridge decks. The primary properties investigated were: bonding to cracked surfaces, flow characteristics, ease of
application, and mechanical characteristics. This paper discusses these properties, matrix performance and matrix
viability for use in automated nondestructive robotic delivery system to fill delaminations and narrow/hairline crack in
bridge decks.
Multisensor data fusion for nondestructive evaluation of bridge decks
Ying Zhang,
Xiangmin Wei,
Zhenhua Xie
Show abstract
The nondestructive evaluation (NDE) of bridge decks often requires a combination of different methods for deterioration
identification and characterization. Each individual NDE method also needs the responses of an array of spatially
distributed sensors to better detect damages. Proper interpretation techniques are needed to effectively integrate data
from different NDE technologies and sensor arrays of a single NDE method. A hybrid multisensor data fusion
framework is presented in the paper for the NDE of bridge decks. The multisensor data fusion approach process,
integrate and interpret the data from multisensor data of a single NDE method and a combination of various NDE
technologies in a way that improves the accuracy and reliability of deterioration identification and characterization.
Evaluation of corrosion effect in reinforced concrete by chloride exposure
Show abstract
Durability is generally described as the ability of a material to maintain its physical and mechanical properties over time.
In reinforced concrete (RC) structures, concrete is the ideal material to protect the steel reinforcement given its high
alkalinity. In environments subjected to highly aggressive conditions, mostly due to the presence of chlorides, concrete
may lose its protective characteristics and allow for accelerated ageing. Concrete degradation and steel reinforcement
corrosion are phenomena closely connected. The aim of this research work is the characterization of the relationship
between steel reinforcement corrosion and concrete degradation under accelerated ageing in a 3% sodium chloride
solution. The method of linear polarization is used for identification of the corrosion rate of the steel bar. Additionally,
the values of concrete residual strength are obtained, and correlated to both the corrosion rate and width of concrete
cracks. Finally, the prediction of the concrete cover useful life is estimated.
Laser, Ultrasound, Acoustic Emission NDE II
Assessment of carbon fiber-reinforced polyphenylene sulfide by means of laser ultrasound
Show abstract
From automobile industry to aerospace, thermoformed composites are more and more in use. Thermoplastics offer a
number of attractive applications in commercial use like short production times, tailored solutions, recyclability and
lower cost. The thermoforming process allows for producing carbon fiber-reinforced parts in a wide range of different
geometric shapes. On the other hand this benefit requires a demanding nondestructive testing procedure especially for
security relevant parts. A contactless method which is able to fulfil this requirement is the extension of the ultrasound
technique with laser technology. It opens up new opportunities for quality assessment during manufacturing like
inspection of complex surfaces including small radii, remote observation and nondestructive testing of hot items directly
after the thermal forming process. We describe the successful application of laser-based ultrasound on small complex
thermoformed composite parts (Cetex® PPS). Cetex consists of semicrystalline polyphenylene sulfide thermoplastics
providing outstanding toughness and excellent chemical and solvent resistance. It is qualified in aircraft industry for
multiple structural applications. For instance, Cetex is used in the Airbus A380 engine air intakes and the wing fixed
leading edge (J-Nose). We investigated several test samples with intentionally introduced defects. The smallest flaw size
detected was 2 mm in diameter for delaminations and 6 mm in diameter for porosity.
Development of a portable ultrasonic phased array inspection imaging apparatus for NDT
Show abstract
To improve the inspection result repetition and reliability of manual ultrasonic method in NDT field, a portable ultrasonic
apparatus based on the phased array inspection technology is developed in paper. The apparatus is small, integrated and
portable, which can perform the shear wave and longitudinal wave detection, automatically transmit and receive sound
wave, accomplish data acquisition in real time, provide many imaging modes, and give comments of the damage. As
designed, the apparatus can implement different algorithm of the ultrasonic phased array inspection technology. With
proposed inspection scheme, a phased array reference block was practically detected in the lab. Experiment results
indicate the portable ultrasonic apparatus can factually imaging the flaws position, and the size and shape of flaws are
nearly consistent with the practical condition. Compared to the conventional ultrasonic testing system, the current
apparatus works more efficiently and reliably in the flaw detection and evaluation.
NDE in Civil Infrastructure II
Temperature effect on modal frequencies for a rigid continous bridge based on long term monitoring
Show abstract
Environment conditions such as temperature, humidity, traffic loadings and wind loadings cause changes in the
identified dynamic properties of bridges, which will affect health diagnosis based on the mode frequencies in bridge
structural health monitoring. This paper analyzed temperature effects on a rigid continuous bridge based on monitoring
data from Aug. 2006 to Dec. 2006. First, temperature data calculating process from measured data is given and
frequency time histories are graphed. Temperature effects on the bridge dynamic properties are divided into yearly
temperature change and sunlight radiation. Then, theoretical eigenfrequency functions of a simply-supported uniform
beam with and without axial force are provided to explain and distinguish temperature effects and constraints on
characteristic frequencies. Relationship of measured temperature and frequencies data are drafted and linear correlations
are found on the 1st and 3rd vertical frequencies. 2nd vertical frequency fluctuated cyclically in one day, caused by
sunlight radiation and restrains.
Bridge reliability assessment based on the PDF of long-term monitored extreme strains
Meiju Jiao,
Limin Sun
Show abstract
Structural health monitoring (SHM) systems can provide valuable information for the evaluation of bridge performance.
As the development and implementation of SHM technology in recent years, the data mining and use has received
increasingly attention and interests in civil engineering. Based on the principle of probabilistic and statistics, a reliability
approach provides a rational basis for analysis of the randomness in loads and their effects on structures. A novel
approach combined SHM systems with reliability method to evaluate the reliability of a cable-stayed bridge instrumented
with SHM systems was presented in this paper. In this study, the reliability of the steel girder of the cable-stayed bridge
was denoted by failure probability directly instead of reliability index as commonly used. Under the assumption that the
probability distributions of the resistance are independent to the responses of structures, a formulation of failure
probability was deduced. Then, as a main factor in the formulation, the probability density function (PDF) of the strain at
sensor locations based on the monitoring data was evaluated and verified. That Donghai Bridge was taken as an example
for the application of the proposed approach followed. In the case study, 4 years' monitoring data since the operation of
the SHM systems was processed, and the reliability assessment results were discussed. Finally, the sensitivity and
accuracy of the novel approach compared with FORM was discussed.
Risk based bridge data collection and asset management and the role of structural health monitoring
Show abstract
Bridges are critical to the operation and functionality of the whole road networks. It is therefore essential that specific
data is collected regarding bridge asset condition and performance, as this allows proactive management of the assets and
associated risks and more accurate short and long term financial planning. This paper proposes and discusses a strategy
for collection of data on bridge condition and performance. Recognizing that risk management is the primary driver of
asset management, the proposed strategy prioritizes bridges for levels of data collection including core, intermediate and
advanced. Individual bridges are seen as parts of wider networks and bridge risk and criticality assessment emphasizes
bridge failure or underperformance risk in the network context. The paper demonstrates how more reliable and detailed
data can assist in managing network and bridge risks and provides a rationale for application of higher data collection
levels for bridges characterized by higher risk and criticality. As the bridge risk and/or criticality increases planned and
proactive integration of structural health monitoring (SHM) data into asset management is outlined. An example of
bridge prioritization for data collection using several bridges taken from a national highway network is provided using an
existing risk and criticality scoring methodology. The paper concludes with a discussion on the role of SHM in data
collection for bridge asset management and where SHM can make the largest impacts.
NASA-based NDE/SHM Activities
High-speed AMB machining spindle model updating and model validation
Show abstract
High-Speed Machining (HSM) spindles equipped with Active Magnetic Bearings (AMBs) have been envisioned to be
capable of automated self-identification and self-optimization in efforts to accurately calculate parameters for stable
high-speed machining operation. With this in mind, this work presents rotor model development accompanied by
automated model-updating methodology followed by updated model validation. The model updating methodology is
developed to address the dynamic inaccuracies of the nominal open-loop plant model when compared with experimental
open-loop transfer function data obtained by the built in AMB sensors. The nominal open-loop model is altered by
utilizing an unconstrained optimization algorithm to adjust only parameters that are a result of engineering assumptions
and simplifications, in this case Young's modulus of selected finite elements. Minimizing the error of both resonance
and anti-resonance frequencies simultaneously (between model and experimental data) takes into account rotor natural
frequencies and mode shape information. To verify the predictive ability of the updated rotor model, its performance is
assessed at the tool location which is independent of the experimental transfer function data used in model updating
procedures. Verification of the updated model is carried out with complementary temporal and spatial response
comparisons substantiating that the updating methodology is effective for derivation of open-loop models for predictive
use.
Detecting cracks in ceramic matrix composites by electrical resistance
Show abstract
The majority of damage in SiC/SiC ceramic matrix composites subjected to monotonic tensile loads is in the form of
distributed matrix cracks. These cracks initiate near stress concentrations, such as 90° fiber tows or large matrix pores
and continue to accumulate with additional stress until matrix crack saturation is achieved. Such damage is difficult to
detect with conventional nondestructive evaluation techniques (immersion ultrasonics, x-ray, etc.). Monitoring a
specimen's electrical resistance change provides an indirect approach for monitoring matrix crack density. Sylramic-iBN
fiber- reinforced SiC composites with a melt infiltrated (MI) matrix were tensile tested at room temperature.
Results showed an increase in resistance of more than 500% prior to fracture, which can be detected either in situ or
post-damage. A relationship between resistance change and matrix crack density was also determined.
NDE in Composites
Carbon nanotube yarn sensors for structural health monitoring of composites
Show abstract
With increasing application of composite materials, real time monitoring of composite structures becomes vital for
maintenance purpose as well as prevention of catastrophic failure. It has been reported that carbon nanotubes (CNTs)
have excellent piezoresistive properties, which may enable a new generation of sensors in nano or micro scales. We
report here a novel prototype of carbon nanotube yarn sensors with excellent repeatability and stability for in-situ
structural health monitoring. The CNT yarn is spun directly from CNT arrays, and its electrical resistance increases
linearly with tensile strain, which makes it an ideal strain sensor. Importantly, it shows repeatable piezoresistive behavior
under repetitive straining and unloading. Yarn sensors show stable resistances at temperatures ranging from -196° to
110°. Neat yarn sensors are also embedded into resin to monitor the loading conditions of the composites. With
multiple yarn sensor elements aligned in the composite, the crack initiation and propagation could be monitored. Yarn
sensors could be easily incorporated into composite structures with minimal invasiveness and weight penalty to enable
the structure has self-sensing capabilities.
Interaction of surface waves induced by IDT sensors with flaws in fiberglass composite panels
Show abstract
Polyester resin based glass fiber reinforced composite panels obtained from a local windmill turbine blade part
manufacturing company are used to evaluate the performance of inter-digital transducer (IDT) surface wave transducers.
Interaction of surface waves with fiberglass layers is addressed in this work. Additionally, artificially created flaws such
as cracks, impact damage and delamination are also studied in terms of amplitude changes in order to attempt to quantify
the size, location and severity of damage in the test panels. As a potential application to the structural health monitoring
(SHM) of windmill turbine blades, the coverage distance within the width of the sound field is estimated to be over 80
cm when a set of IDT sensors consisted of one transmitter and two receivers in a pitch-catch mode.
Non-invasive damage detection in composite beams using marker extraction and wavelets
Show abstract
Simple and contactless methods for determining the health of metallic and composite structures are necessary
to allow non-invasive Non-Destructive Evaluation (NDE) of damaged structures. Many recognized damage
detection techniques, such as frequency shift, generalized fractal dimension and wavelet transform, have been
described with the aim to identify, locate damage and determine the severity of damage. These techniques are
often tailored for factors such as (i) type of material, (ii) damage patterns (crack, impact damage, delamination),
and (iii) nature of input signals (space and time). In this paper, a wavelet-based damage detection framework
that locates damage on cantilevered composite beams via NDE using computer vision technologies is presented.
Two types of damage have been investigated in this research: (i) defects induced by removing material to reduce
stiffness in a metallic beam and (ii) manufactured delaminations in a composite laminate. The novelty in the
proposed approach is the use of bespoke computer vision algorithms for the contactless acquisition of modal
shapes, a task that is commonly regarded as a barrier to practical damage detection. Using the proposed
method, it is demonstrated that modal shapes of cantilever beams can be readily reconstructed by extracting
markers using Hough Transform from images captured using conventional slow motion cameras. This avoids
the need to use expensive equipment such as laser doppler vibrometers. The extracted modal shapes are then
used as input for a wavelet transform damage detection, exploiting both discrete and continuous variants. The
experimental results are verified using finite element models (FEM).
Characterization of random heterogeneities in polycrystalline microstructures using wave propagation simulation
Show abstract
The quantification of variability in the mechanical behavior of metallic materials is important in the design and
reliability assessment of mechanical components. A combination of experimental and computational approaches
is often required to alleviate the experimental burden and lack of data in constructing a probabilistic formalism
for material design. The present work aims at integrating material characterization and computational modeling
for the evaluation of variability in the elastodynamic response of random polycrystals. First, a procedure is
presented for simulation of random 2D polycrystalline microstructures from limited experimental data. Second,
the capability of the numerical model in capturing the variation of the scattered waves due to the random
heterogeneities is investigated by introducing a suitable quantity of interest characterizing the intensity of the
fluctuations of the stochastic waveforms. Two important types of heterogeneities are considered. The first is the
inherent heterogeneity due to the mismatch in the grain orientations. The second is the heterogeneity due to fine
scale defects in the form of random intergranular micro-cavities. The numerical model presented in this paper
can be useful for the interpretation of experimental ultrasonic measurements for random heterogeneous material.
The result is also applicable to the validation of multiscale probabilistic models for material prognosis.
Coupled attenuation and multiscale damage model for composite structures
Show abstract
Composite materials are widely used in many applications for their high strength, low weight, and tailorability for
specific applications. However, the development of robust and reliable methodologies to detect micro level damage in
composite structures has been challenging. For composite materials, attenuation of ultrasonic waves propagating through
the media can be used to determine damage within the material. Currently available numerical solutions for attenuation
induce arbitrary damage, such as fiber-matrix debonding or inclusions, to show variations between healthy and damaged
states. This paper addresses this issue by integrating a micromechanics analysis to simulate damage in the form of a
fiber-matrix crack and an analytical model for calculating the attenuation of the waves when they pass through the
damaged region. The hybrid analysis is validated by comparison with experimental stress-strain curves and piezoelectric
sensing results for attenuation measurement. The results showed good agreement between the experimental stress-strain
curves and the results from the micromechanics analysis. Wave propagation analysis also showed good correlation
between simulation and experiment for the tested frequency range.
Effect of fiber surface conditioning on the acoustic emission behavior of steel fiber reinforced concrete
Show abstract
The role of coating in preserving the bonding between steel fibers and concrete is investigated in this paper. Straight
types of fibers with and without chemical coating are used in steel fiber reinforced concrete mixes. The specimens are
tested in bending with concurrent monitoring of their acoustic emission activity throughout the failure process using two
broadband sensors. The different stages of fracture (before, during and after main crack formation) exhibit different
acoustic fingerprints, depending on the mechanisms that are active during failure (concrete matrix micro-cracking,
macro-cracking and fiber pull out). Additionally, it was seen that the acoustic emission behaviour exhibits distinct
characteristics between coated and uncoated fiber specimens. Specifically, the frequency of the emitted waves is much
lower for uncoated fiber specimens, especially after the main fracture incident, during the fiber pull out stage of failure.
Additionally, the duration and the rise time of the acquired waveforms are much higher for uncoated specimens. These
indices are used to distinguish between tensile and shear fracture in concrete and suggest that friction is much stronger
for the uncoated fibers. On the other hand, specimens with coated fibers exhibit more tensile characteristics, more likely
due to the fact that the bond between fibers and concrete matrix is stronger. The fibers therefore, are not simply pulled
out but also detach a small volume of the brittle concrete matrix surrounding them. It seems that the effect of chemical
coating can be assessed by acoustic emission parameters additionally to the macroscopic measurements of ultimate
toughness.
Inspection for kissing bonds in composite materials using vibration measurements
Show abstract
Improper bonding of composite structures can result in close contact cracks under compressive stresses, called kissing
bonds. These bond defects are very difficult to detect using conventional inspection techniques such as tap testing or
local ultrasonic scanning and can lead to local propagation of damage if the structure is subjected to crack opening
stresses.
A method is investigated for identifying kissing bonds in composite material repairs based on vibration measurements.
A damage feature of the kissing bond is extracted from the response of the input-output measurement that is a function of
the structural path. This path exhibits local decoupling associated with the close contact cracks. Experimental vibration
measurements from sandwich composite materials are presented along with the results of the damage detection algorithm
for the healthy sections of the material and the kissing bond sections.
A vibration based inspection technique could increase the ability to detect kissing bonds in composite material repairs
while decreasing inspection time. Benefits of this method of identification over conventional techniques include its
robust, objective damage detection methodology and the reduced requirement for specimen preparation and surface
texture when compared to ultrasonic scanning.
PNNL-based NDE in Homeland Security Applications
X-ray scan detection for cargo integrity
Show abstract
The increase of terrorism and its global impact has made the determination of the contents of cargo containers a
necessity. Existing technology allows non-intrusive inspections to determine the contents of a container rapidly and
accurately. However, some cargo shipments are exempt from such inspections. Hence, there is a need for a technology
that enables rapid and accurate means of detecting whether such containers were non-intrusively inspected. Non-intrusive
inspections are most commonly performed utilizing high powered X-ray equipment. The challenge is creating a
device that can detect short duration X-ray scans while maintaining a portable, battery powered, low cost, and easy to
use platform. The Pacific Northwest National Laboratory (PNNL) has developed a methodology and prototype device
focused on this challenge.
The prototype, developed by PNNL, is a battery powered electronic device that continuously measures its X-ray and
Gamma exposure, calculates the dose equivalent rate, and makes a determination of whether the device has been
exposed to the amount of radiation experienced during an X-ray inspection. Once an inspection is detected, the device
will record a timestamp of the event and relay the information to authorized personnel via a visual alert, USB
connection, and/or wireless communication.
The results of this research demonstrate that PNNL's prototype device can be effective at determining whether a
container was scanned by X-ray equipment typically used for cargo container inspections. This paper focuses on
laboratory measurements and test results acquired with the PNNL prototype device using several X-ray radiation levels.
A wireless sensor tag platform for container security and integrity
Show abstract
Cargo containers onboard ships are widely used in the global supply chain. The need for container security is evidenced
by the Container Security Initiative launched by the U.S. Bureau of Customs and Border Protection (CBP). One method
of monitoring cargo containers is using low power wireless sensor tags. The wireless sensor tags are used to set up a
network that is comprised of tags internal to the container and a central device. The sensor network reports alarms and
other anomalies to a central device, which then relays the message to an outside network upon arrival at the destination
port. This allows the port authorities to have knowledge of potential security or integrity issues before physically
examining the container. Challenges of using wireless sensor tag networks for container security include battery life,
size, environmental conditions, information security, and cost among others. PNNL developed an active wireless sensor
tag platform capable of reporting data wirelessly to a central node as well as logging data to nonvolatile memory. The
tags, operate at 2.4 GHz over an IEEE 802.15.4 protocol, and were designed to be distributed throughout the inside of a
shipping container in the upper support frame. The tags are mounted in a housing that allows for simple and efficient
installation or removal prior to, during, or after shipment. The distributed tags monitor the entire container volume. The
sensor tag platform utilizes low power electronics and provides an extensible sensor interface for incorporating a wide
range of sensors including chemical, biological, and environmental sensors.
Application and assessment of ultrasonic inspection methods for flaw detection and characterization of manganese steel frogs
Show abstract
Ultrasonic nondestructive examination (NDE) has a long and successful history of application across a wide array of
industries, including nuclear, aerospace, and transportation sectors. In coarse-grained, cast Manganese (Mn) steel frog
components, NDE/inspection challenges are encountered both in-field (after the frogs have been installed on a rail line)
and at the manufacturing facilities during post-fabrication QA/QC activities. Periodically inherently flawed frogs are
received from a manufacturer, and put into service, as most railroad operators do not have a means to conduct pre-service
examinations on received components. Accordingly, there is a need for a pre-service inspection system that can
provide a rapid, cost-effective and non-intrusive inspection capability for detection of defects, flaws, and other
anomalies in frog components, in order to avoid premature initiation of cracks or failures of these components during
service. This study focused on evaluating use of a volumetric phased-array ultrasonic testing (PA-UT) method to
monitor fabrication quality assurance. In this preliminary assessment of using PA-UT, data were acquired at a frequency
of 2.0 MHz on a known, flawed Mn steel frog component directly from a manufacturing facility. The component
contained flaws commonly found as a result of the manufacturing process of these cast rail components. The data were
analyzed and the anomalies were detected, localized and characterized. Results were compared against baseline
radiographic data. A detection metric was reported in the form of signal-to-noise values.
NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems I
Long-term assessment of an autonomous wireless structural health monitoring system at the new Carquinez Suspension Bridge
Show abstract
A dense network of sensors installed in a bridge can continuously generate response data from which the health and
condition of the bridge can be analyzed. This approach to structural health monitoring the efforts associated with
periodic bridge inspections and can provide timely insight to regions of the bridge suspected of degradation or damage.
Nevertheless, the deployment of fine sensor grids on large-scale structures is not feasible using wired monitoring
systems because of the rapidly increasing installation labor and costs required. Moreover, the enormous size of raw
sensor data, if not translated into meaningful forms of information, can paralyze the bridge manager's decision making.
This paper reports the development of a large-scale wireless structural monitoring system for long-span bridges; the
system is entirely wireless which renders it low-cost and easy to install. Unlike central tethered data acquisition systems
where data processing occurs in the central server, the distributed network of wireless sensors supports data processing.
In-network data processing reduces raw data streams into actionable information of immediate value to the bridge
manager. The proposed wireless monitoring system has been deployed on the New Carquinez Suspension Bridge in
California. Current efforts on the bridge site include: 1) long-term assessment of a dense wireless sensor network; 2)
implementation of a sustainable power management solution using solar power; 3) performance evaluation of an
internet-enabled cyber-environment; 4) system identification of the bridge; and 5) the development of data mining tools.
A hierarchical cyber-environment supports peer-to-peer communication between wireless sensors deployed on the
bridge and allows for the connection between sensors and remote database systems via the internet. At the remote
server, model calibration and damage detection analyses that employ a reduced-order finite element bridge model are
implemented.
Networked computing in wireless sensor networks for structural health monitoring
Show abstract
This paper studies the problem of distributed computation over a wireless network of resource constrained sensor
nodes. In particular, we focus our attention on sensor networks used for structural health monitoring. Within
this context, the heaviest computation is to determine the singular value decomposition (SVD) to extract mode
shapes (eigenvectors) of a structure. Compared to collecting raw vibration data and performing SVD at a
central location, computing SVD within the network can result in a significantly smaller energy consumption
and delay. Recent results have proposed methods to decompose SVD into components that can be carried out in
a distributed way. The focus of this paper is to determine a near-optimal communication structure that enables
the distribution of this computation and the reassembly of the final results, with the objective of minimizing
energy consumption subject to a computational delay constraint. We show that this reduces to a generalized
clustering problem; a cluster forms a unit on which a component of the overall computation is performed. We
establish that this problem is NP-hard. By relaxing the delay constraint, we derive a lower bound to this problem.
We also show that the optimal solution to the unconstrained problem has a simple structure that reveals insights
into the solution of the original constrained problem. We then propose an integer linear program (ILP) to solve
the constrained problem exactly as well as an approximate algorithm with a proven approximation ratio. We
also present a distributed version of the approximate algorithm. Numerical results are presented.
Energy harvesting of radio frequency and vibration energy to enable wireless sensor monitoring of civil infrastructure
Tzeno Galchev,
James McCullagh,
Rebecca L. Peterson,
et al.
Show abstract
To power distributed wireless sensor networks on bridges, traditional power cables or battery replacement are
excessively expensive or infeasible. This project develops two power harvesting technologies. First, a novel parametric
frequency-increased generator (PFIG) is developed. The fabricated PFIG harvests the non-periodic and unprecedentedly
low frequency (DC to 30 Hz) and low acceleration (0.55-9.8 m/s2) mechanical energy available on bridges with an
average power > 2 μW. Prototype power conversion and storage electronics were designed and the harvester system was
used to charge a capacitor from arbitrary bridge-like vibrations. Second, an RF scavenger operating at medium and
shortwave frequencies has been designed and tested. Power scavenging at MHz frequencies allows for lower antenna
directivities, reducing sensitivity to antenna positioning. Furthermore, ambient RF signals at these frequencies have
higher power levels away from cities and residential areas compared to the UHF and SHF bands utilized for cellular
communication systems. An RF power scavenger operating at 1 MHz along with power management and storage
circuitry has been demonstrated. It powers a LED at a distance of 10 km from AM radio stations.
The development of chloride ion selective polypyrrole thin film on a layer-by-layer carbon nanotube working electrode
Show abstract
A chloride ion selective thin film sensor is proposed for measuring chloride ion concentration, which is an
environmental parameter correlated to corrosion. In this work, electrochemical polymerization of Polypyrrole (PPy)
doped with chloride ions was achieved on the top of a carbon nanotube (CNT) thin film as a working electrode in an
electrochemical cell. The underlying CNT layer conjugated with doped PPy thin film can form a multifunctional "selfsensing"
material platform for chloride ion detection in a concrete environment. The paper presents the first type of work
using CNT and PPy as hybrid materials for chloride ion sensing. Electrochemical polymerization of PPy results in
oxidation that yields an average of one positive charge distributed over four pyrrole units. This positive charge is
compensated by negatively-charged chloride ions in the supporting electrolyte. In effect, the chloride ion-doped PPy has
become molecularly imprinted with chloride ions thereby providing it with some degree of perm-selectivity for chloride
ions. The detection limit of the fabricated chloride ion-doped PPy thin film can reach 10-8 M and selectivity coefficients
are comparable to those in the literature. The reported work aims to lay a strong foundation for detecting chloride ion
concentrations in the concrete environment.
Mechanical and electrical characterization of self-sensing carbon black ECC
Show abstract
In this paper, the development of a new variation of Engineered Cementitious Composite (ECC) that aims to combine
tensile ductility with self-sensing ability is described. ECC is a new type of high-performance fiber reinforced
cementitious composite that exhibits strain-hardening under applied tensile load while resisting fracture localization. The
self-sensing ability is achieved by incorporating a small dosage of carbon black (CB) into the ECC system (hereafter
known as CB-ECC) to enhance its piezoresistive behavior while maintaining its tensile strain-hardening behavior. The
tensile stress-strain response of CB-ECC is studied with an emphasis on its tensile stress and strain capacity, as well as
its cracking pattern. In addition, the piezoresistive behavior of CB-ECC under uniaxial tension is investigated.
Specifically, the effect of carbon black content on the electrical properties of ECC including the sensitivity of changes in
its bulk conductivity under applied tensile strain are explored in detail.
Fiber Optics Sensors Technologies
A quasi-distributed optical fiber sensor network for large strain and high-temperature measurements of structures
Show abstract
Due to earthquake effects, buildings often experience large strains, leading to progressive collapses. Monitoring and
assessing the large strain condition of critical buildings is of paramount importance to post-earthquake responses and
evacuations in earthquake-prone regions. However, few monitoring system can work under such harsh environments.
For their unique attributes such as compactness, immunity to electromagnetic interference and capability integrated
within various types of structures and materials, optical fiber sensors are especially attractive for quasi-distributed
strain sensing purposes in harsh environments. Nevertheless, the dynamic range of strain measurements of an optical
sensor is limited by the elasticity of the optical fiber. In this paper, a quasi-distributed optical fiber sensor network
based on extrinsic Fabry-Perot interferometer (EFPI) and long-period fiber grating (LPFG) sensors for both large strain
and high temperature measurements has been developed. The sensor network combined several inline EFPIs and
LPFGs by various couplers. Each EFPI sensor in the sensor network system has the capacity of large strain
measurement up to 12% and each LPFG sensor here has a temperature measurement range of up to 700°C. To obtain
strain and temperature information for multiple locations more efficiently, a hybrid LPFG/EFPI optical fiber sensor
based sensor network system has been studied in this paper. Experimental results demonstrate that the proposed quasi-distributed
optical fiber sensor network system is capable for both large strain and high temperature measurements.
Therefore, the proposed optical fiber sensor network system can be applied to monitor the quasi-distributed strain of
civil infrastructure in harsh environments.
Highly dense strain measurement of concrete retrofitted with smart fabric
Show abstract
A significant technical advancement in distributed fiber optic strain sensors has been accomplished: Brillouin optical
correlation domain analysis (BOCDA) provides a high spatial resolution and the smallest measurement interval due to
Brillouin scattering stimulated by the correlation of two counter-propagating lightwaves. In a BOCDA-based system, the
measurement position can be varied continuously by changing the modulation frequency, whereas other systems require
a sophisticated A/D board for localizing the measurement position. In fact, 50 mm is the current limit of the
measurement interval in conventional time-domain-based systems, because higher sampling rates are required to process
information traveling at the speed of lightwaves. This paper presents an experimental study on cracked concrete
specimen retrofitted with a ply of smart fabric; a fiber optic sensor (FOS) is woven into the fabric. The strain distribution
along the sensing fiber is measured to detect the debonding of the smart fabric from the concrete specimen under loading,
and the measured highly dense strain information obtained using BOCDA is found to potentially facilitate a better
understanding of structural behavior.
Stability and reliability of fiber optic measurement systems: basic conditions for successful long term structural health monitoring
Show abstract
Recent developments in fiber optic sensors for monitoring civil structures have been of great help for engineers dealing
with these structures. After literature survey it is observed that while using fiber optic sensor system for health
monitoring of civil structures not much attention is given to the core quality of the fiber, types of coating on fiber,
implementing methodologies, handling of fiber optic sensors and their long term effect on reliability of the performance
of the monitoring system. These issues are important because the structural conditions, stress level and environment in
which fiber optic sensors are placed are different from telecommunication industry. In this paper issues related to long
term structural health monitoring of civil structures are investigated. The issue of the fatigue property of optic fiber is
discussed since reversal bending of the fiber may cause adverse effect on the light carrying capacity of the fiber. Other
long term structural health monitoring (SHM) issues such as life of fiber, strain transfer process from fiber core to
coating, calibration of fiber and selection of fiber are also discussed based on the experiments carried out for successful
implementation of long term health monitoring of civil structures. The main objective of these experiments is to come up
with comprehensive long term structural health monitoring system for strain measurement.
Nanofilm-coated long-period fiber grating humidity sensors for corrosion detection in structural health monitoring
Show abstract
Long-period gratings (LPGs) have shown their significant promising applications in sensors owing to the attractive
features that they posses such as small size, immunity for electromagnetic interference, geometric versatility,
multiplexing capability, and resistance to corrosive and hazardous environments. Recent researches have revealed that
LPGs written on the standard optical fibers could be used as a powerful sensing platform for structural health
monitoring. In this work, we inscribe LPGs into SMF-28 optical fiber by focused-beam CO2 laser, demonstrating as a
refractive index sensor for nondestructive chemical detections in the civil infrastructures. Although evanescent-field
based LPG sensors have been applied in quantitatively monitoring chemical analytes including moisture, chloride, and
corrosion by-product, etc., the sensitivity, selectivity, and response time as well as thermo-stability of such sensors are
still the issues for some special purposes. In order to improve those characteristics of the sensors, we propose two types
of nano-film to be coated in grating region by electrostatic self-assembly (ESA) deposition processing. The primary
coating does not affect on LPG transmission parameters such as resonance wavelength and its intensity that can be used
for sensing, but it increases the sensitivity to refractive index change of surrounding material. The secondary coating is
for selectively absorption of analyte molecule of interest. Response time of the nanofilm-coated LPG sensor is dependent
on the analyte absorption and de-absorption rates as well as the thicknesses of the coating materials, which is also
investigated. Multi-channel sensor system is being designed to monitor different analytes simultaneously, which is
continuing to further explore the monitoring of structural health conditions through in situ measurements of corrosion in
the concrete structures.
Condition monitoring and life-cycle cost design of stay cable by embedded OFBG sensors
Show abstract
Stay cables are one of the most critical structural components of a cable-stayed bridge. However, stay cables readily
suffer from fatigue damage, corrosion damage and their coupled effect. Thus, condition monitoring of stay cables is
important to ensure the integrity and safety of a bridge. Glass Fibre Reinforced Polymer Optical Fibre Bragg Grating
(GFRP-OFBG) cable, a kind of fibre Bragg grating optical sensing technology-based smart stay cables is used in this
study. The application of the smart stay cables on the Tianjin Yonghe Bridge was demonstrated and the vehicle live load
effect and fatigue effect of smart stay cables were evaluated based on field monitoring data. Furthermore, the life-cycle
cost analysis method of the stay cables is established. Finally, based on the nonlinear reliability index deterioration
model, the optimal design of stay cable with different reference period is evaluated.
Integrating single-point vibrometer and full-field electronic speckle pattern interferometer to evaluate a micro-speaker
Show abstract
A testing system contains an advanced vibrometer/interferometer device (AVID) and a high-speed electronic
speckle pattern interferometer (ESPI) was developed. AVID is a laser Doppler vibrometer that can be used to detect
single-point linear and angular velocity with DC to 20 MHz bandwidth and with nanometer resolution. In swept
frequency mode, frequency response from mHz to MHz of the structure of interest can be measured. The ESPI
experimental setup can be used to measure full-field out-of-plane displacement. A 5-1 phase shifting method and a
correlation algorithm were used to analyze the phase difference between the reference signal and the speckle signal
scattered from the sample surface. In order to show the efficiency and effectiveness of AVID and ESPI, we designed a
micro-speaker composed of a plate with fixed boundaries and two piezo-actuators attached to the sides of the plate. The
AVID was used to measure the vibration of one of the piezo-actuators and the ESPI was adopted to measure the two-dimensional
out-of-plane displacement of the plate. A microphone was used to measure the acoustic response created by
the micro-speaker. Driving signal includes random signal, sinusoidal signal, amplitude modulated high-frequency carrier
signal, etc. Angular response induced by amplitude modulated high-frequency carrier signal was found to be
significantly narrower than the frequency responses created by other types of driving signals. The validity of our newly
developed NDE system are detailed by comparing the relationship between the vibration signal of the micro-speaker and
the acoustic field generated.
NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems II
A fast inversion analysis algorithm for the spectral analysis of surface wave (SASW) method
Show abstract
Spectral Analysis for Surface Wave (SASW) is a widely practiced NDT method due to its ability to identify the
shear velocity profile of subsurface layers. However, the SASW method is limited to point-to-point inspection
because all data has to go through an inversion process, which is iterative and manual. Some automated iteration
techniques were developed to improve the efficiency of inversion analysis. These attempts did not change the
situation much because they were still based on the guess-and-check procedure incorporated with a forward analysis.
In this paper, a new inversion analysis algorithm is proposed to estimate the shear velocity profile rapidly without
performing conventional forward analysis. Unlike conventionally determining the dispersion curve with a stiffness
matrix or something similar, the dispersion curve of a layered structure is assumed to be a weighted combination of
the shear velocity profile. The weighting factors are determined according to the variation of particle displacement
with depth for a specified wavelength of surface wave. Based on this assumption, a fast inversion algorithm is
established to estimate the shear velocity profile from a given dispersion curve. No prior knowledge of the test site
or personal expertise is needed because this method does not require the initial values of the layer depths and shear
velocities. This new method allows the SASW method to be a fully automatic or even real-time reporting method for
highway pavement detection. The accuracy of this fast inversion algorithm is verified by comparing the results to
those of the conventional algorithm.
Wave number estimation based method on in situ pavement ground truth with near source-receiver sensing
Show abstract
SASW (Spectral Analysis of Surface Waves) is practical and relatively effective in characterizing subsurface ground
truth. According to the surface wave in the interesting range of frequency, some criteria for source-receiver configuration
are employed and limit the applications. Challenges emerge when SASW is applied to study the surface wave involving
multiple modes effect and when the source is near the receiver. In such cases, multiple modes effects and evanescent
wave fields are present in array sensing and might weaken the inversion accuracy of pavement subsurface profile. In this
work, these issues were investigated and a complex wave number estimation based method was proposed. The complex
wave number was estimated by iterative linear exponential fitting from wave field model to response measurements.
Evanescent wave for near field and multiple modes effects were focused in the proposed method. Finally, simulated
signals from FEA model were processed to demonstrate the algorithm and the results were discussed.
Compact programmable ground-penetrating radar system for roadway and bridge deck characterization
Dan Busuioc,
Tian Xia,
Anbu Venkatachalam,
et al.
Show abstract
A compact, high-performance, programmable Ground Penetrating Radar (GPR) system is described
based on an impulse generator transmitter, a full waveform sampling single shot receiver, and high
directivity antennas.
The digital programmable pulse generator is developed for the transmitter circuit and both the pulse
width and pulse shape are tunable to adjust for different modes of operation. It utilizes a step-recovery
diode (SRD) and short-circuited microstrip lines to produce
sub-nanosecond wide ultra-wideband
(UWB) pulses. Sharp step signals are generated by periodic clock signals that are connected to the
SRD's input node. Up to four variable width pulses (0.8, 1.0, 1.5, and 2.1 ns) are generated through a
number of PIN switches controlling the selection of different microstrip lengths. A schottky diode is
used as a rectifier at the output of the SRD in order to pass only the positive part of the Gaussian pulses
while another group of short-circuit microstrips are used to generate amplitude-reversed Gaussian
pulses. The addition of the two pulses results in a Gaussian monocycle pulse which is more energy
efficient for emission.
The pulse generator is connected to a number of UWB antennas. Primarily, a UWB Vivaldi antenna
(500 MHz to 5 GHz) is used, but a number of other high-performance GPR-oriented antennas are
investigated as well. All have linear phase characteristic, constant phase center, constant polarization
and flat gain. A number of methods including resistive loading are used to decrease any resonances due
to the antenna structure and unwanted reflections from the ground. The antennas exhibit good gain
characteristics in the design bandwidth.
Novel low-cost millimeter-wave system for road surface characterization
Dan Busuioc,
Kyle Anstey,
Carey Rappaport,
et al.
Show abstract
A novel low-cost low-complexity design based on Radar technology operating at millimeter wave is presented for
the characterization of road surface conditions in real-time. At frequencies of 24-77 GHz the wavelength is long
enough to obtain slight penetration in the top 1-2" of asphalt or concrete surface, but is also short enough to
resolve details such as crack or pothole depth/etc. The Radar system operates by continuously outputting
radiation and sampling the roadway-reflected radiation through a receiver-downconverter-sampler system.
In initial laboratory testing, the received signal strength was observed to obey the inverse distance 1/R2
relationship. The received signal is further dependent on the incidence angle between the plane of the sensor and
the plane of the roadway. One observation from this is the need of auxiliary sensors for determining the distance
above the road surface as well as providing incident angle data.
The sensor was further mounted on a movable cart used to measure the reflected signal on a variety of road
surfaces (smooth, rough, surface defects, and environment factors such as various levels of moisture). By
comparing measurements of the material after soaking to measurements in the dry state, there is substantial
differentiation in measurements, which indicates the ability to measure the porosity of various materials.
Lastly the sensor bandwidth provides the capability to measure surface roughness illustrated in the standard
deviation of measurement data. On a macroscopic level, the aggregate in a roadway acts as a series of random
scatterers and rough roadways or roadways with surface voids show a large variance between measurements of
nearby points.
Radar/Lidar NDE Technologies
Geometric analysis for the size estimation of subsurface delamination in transient electromagnetic response
Show abstract
Detection of subsurface defects (e.g., delamination, cracking) using microwave/radar sensors (e.g., ground penetrating
radar or GPR) is an important and promising technique for the effective and efficient maintenance of civil
infrastructure. In this technique, reflected and scattered electromagnetic signals are typically collected and used
for interpreting the size and property of subsurface damages. The objective of this paper is to investigate the feasibility
of using finite measurements in the reflected signal for size estimation, through the geometric analysis of
waveform. Simulated transient electromagnetic response was generated by finite difference time domain (FDTD)
methods in two dimensional domain. A modulated Gaussian impulse at a center frequency of 3.5 GHz was used
as the source. Rectangular delaminations with a width ranging from 3.048 cm to 16.256 cm and a thickness of
0.762 cm were considered. The depth of subsurface delamination was also studied. The curvature of reflected
waveforms, obtained by three measurements, was used to correlate with the width of subsurface delamination. A
relative width parameter was defined and used in the proposed equations for estimating the delamination width
with less than 10% error. It is found that the relative width parameter is linearly proportional to the difference in
waveform curvature. The proposed approach is potentially applicable to other subsurface defects with different
shapes.
Development of a baseline model for a steel girder bridge using remote sensing and load tests
Show abstract
A new skewed two span continuous steel girder bridge was constructed and opened to traffic recently. This bridge uses
high performance steel (HPS 100W) in the flanges of the negative moment region over the intermediate pier. For
construction verification and long-term structural health monitoring purposes, a finite element (FE) model was
developed for the bridge superstructure. Various field tests were performed to verify the model: 1) LiDAR scan, 2) static
truck load tests, and 3) Laser doppler vibrometer testing. LiDAR scanner was introduced to gain geometrical information
of the bridge in the real world. It was also used to measure girder deflections during load tests. The fundamental
frequency of the bridge vibration was obtained by using a Laser doppler vibrometer. Both dynamic and static
measurements are then used to update the FE model. This valid bridge superstructure FE model was provided to local
DOT bridge engineers with the completion of this study.
Bridge deck joints evaluation using lidar and aerial photography
Show abstract
Deck joint is important for a bridge - Any cost-effective evaluation methods that can help trace joint movements during
frequent inspections will provide valuable data to bridge engineers. In this paper, 3D Terrestrial LiDAR and Aerial
photography are being investigated as possible joint evaluation methods. The laser scanners record 3D positions of the
surface points, generating high density point clouds. Aerial images taken by commercial DSLR cameras in a small
airplane flying at 1000 feet, generates high resolution imagery. Both techniques have sub-inch pixel resolutions.
Scanning results from bridges in both Florida and Alabama have shown that LiDAR and aerial imaging technologies are
compatible techniques and can be applied in bridge deck joint performance evaluation. Moreover, both techniques have
the potential to reduce the costs in bridge inspection.
3D terrestrial lidar for operational bridge clearance measurements
Show abstract
This paper reports the outcomes of a study of the vehicle crossing effects on terrestrial LiDAR scan on highway bridges
for underclearance measurements. Ground-based or vehicle-mount terrestrial LiDAR scanners, which recreate the bridge
structure as 3D point cloud of thousands of position data points, have been found to be ideal for bridge clearance
measurements. To determine the effects of ambient overhead vehicle crossing and seasonal temperature variation on
clearance measurements, periodic monitoring of the Harris Road Bridge has been conducted. A simplistic but practical
correlation analysis is performed which shows that operational LiDAR scanning is a viable technique for bridge
clearance measurements.
Reliability analysis of 3D lidar bridge evaluation
Show abstract
Terrestrial 3D LiDAR scanner has been suggested as a remote sensing technique for existing and newly constructed
bridges. Using high resolution laser, 3D LiDAR can populate a surficial area with millions of position data points.
Bridge problems can benefit from LiDAR scan and current studies have found potential application including: bridge
clearance, static deflection measurement and damage detection. The technique is especially useful when accurate
measurement of bridge geometry cannot be achieved by traditional survey technique, especially when site topography is
prohibitive. However, resolution is still one of the main reasons that limit the application of LiDAR technology for
advance bridge monitoring. This paper discusses the reliability issues of such technique as well as the LiDAR based
bridge monitoring methodologies. Several experimental results are presented to establish the sensitivities for different
assessments.
NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems III
Development of high-toughness low-viscosity nano-molecular resins for reinforcing pothole patching materials
Show abstract
As the nation's asphalt pavements age and deteriorate, the need for corrective measures to restore safety and rideability
increases. The potholes and alligator cracks in the asphalt pavement of our country's roadways have become an annoying
part of our daily life and no innovative technologies are available to improve the safety of US drivers, reduce the cost of
road maintenance. We have identified a polymeric material, dicyclopentadiene (DCPD) resin, which can be cured by
Grubb's catalyst and other commercially available catalysts to become an ultratough material with all the desired
properties for pothole repair. We have characterized DCPD infiltration characteristics using non-destructive CT scan,
and the mechanical properties using indirect tensile test under hot, cold or wet conditions. The preliminary results show
that DCPD is a promising material for applications in reinforced pothole patching materials.
Development of a wireless monitoring system for fracture-critical bridges
Jeremiah Fasl,
Vasilis Samaras,
Matthew Reichenbach,
et al.
Show abstract
This paper provides a summary of ongoing research sponsored by the National Institute of Standards and Technology
(NIST) that seeks to improve inspection practices for steel bridges by providing the technology and methodology for
real-time monitoring. In order to reduce the time and cost of installing a monitoring system, the research team elected to
use wireless communications within the sensor network. The investigation considered both IEEE 802.11 and IEEE
802.15.4 communications protocols and identified the latter as more practical for bridge monitoring applications. Studies
were conducted to investigate possible improvements in the network performance using high-gain antennas. Results
from experiments conducted outside and on bridges with different antennas are presented in this paper. Although some
benefits were observed using high-gain antennas, the inconsistent performance and higher cost relative to the current
stock, omni-directional antennas does not justify their use.
Low-cost passive sensors for monitoring corrosion in concrete structures
Show abstract
A passive sensor platform has been developed at the University of Texas at Austin to monitor corrosion of embedded
reinforcement in concrete structures. The sensors are powered and interrogated in a wireless manner. Initial sensor
designs used a sacrificial corroding steel wire to indicate the risk of corrosion within concrete. The wire was
physically connected to the sensor circuitry and passed through the circuit protection layer. Consequently, it allowed
contaminants to reach the circuit electric components causing corrosion and limiting the service life of the sensor. A
novel sensor configuration that relies on wireless inductive coupling between a resonant circuit and the transducer
element is presented. The non-contact design eliminates the breach concern and enhances the durability of the senor.
Preliminary test results of the new design will be discussed in this paper.
Nondestructive corrosion detection in concrete through integrated heat induction and IR thermography
Show abstract
Steel corrosion in concrete is a main cause of deterioration and early failure of concrete structures. A novel integration of
electromagnetic heat induction and infrared (IR) thermography is proposed for nondestructive detection of steel
corrosion in concrete, by taking advantage of the difference in thermal characteristics of corroded and non-corroded steel.
This paper focuses on experimental investigation of the concept. An inductive heater is developed to remotely heat the
steel rebar from concrete surface, which is integrated with an IR camera. Bare rebar and concrete samples with different
cover depths are prepared. Each concrete sample is embedded with a single steel rebar in the middle, resulting an
identical cover depth from the front and the back surfaces, which enables heat induction from one surface and IR
thermogrphay from the other simultaneously. The impressed current method is adopted to induce accelerated corrosion
on the rebar. IR video images are recorded during both heating and cooling periods. The test results demonstrate a clear
difference in thermal characteristics between corroded and
non-corroded samples. The corroded samples show higher
rates of heating and cooling as well as a higher peak IR intensity than those of the non-corroded samples. This study
demonstrates a potential for nondestructive detection of rebar corrosion in concrete.
On energy harvesting module for scalable cognitive autonomous nondestructive sensing network (SCANSn) system for bridge health monitoring
Show abstract
The SCANSn is a structural health monitoring (SHM) system is being developed by Acellent Technologies to monitor
steel bridges. The required voltage of the system is 14.4 V for active scanning, and the power consumption is
approximately 8 W. The investigated energy harvesting from both solar and thermal sources to recharge the lithium-ion
battery of the system. A solar panel and a Thermal Electric Generator (TEG) are used to harvest ambient energy. The
thermoelectric device is placed in a Fresnel dome to maximize the temperature gradient of the TEG. During shading of
the solar panel, the TEG continues to supply power to the battery charger. Since the output voltages and currents of the
solar and thermal energy harvesters vary significantly, the energy harvesting module is constructed by two buck-boost
converters operating in parallel. Maximal Power Point Tracking (MPPT) is employed for the buck-boost converter for
the solar panel, while a fixed duty cycle converter is used for the TEG due to substantially lower power compared with
the solar panel. The system design and measured results of a prototype system are presented. Our prototype system
successfully demonstrates that the SCANSn system can be powered by the energy harvested from solar and thermal.
Thermal, Infrared, and Radiographic NDE Technologies
In service damage assessment of bonded composite repairs with full field thermographic techniques
Show abstract
Thermographic techniques offer distinct advantages over other techniques usually employed to assess damage
accumulation and propagation. Among the advantages of these techniques are the fully remote-non contact monitoring
and their ability for full field imaging. Due to the transient nature of the heat transfer phenomenon, phase and lock-in
techniques are of particular interest in order to increase the resolution of the signal or provide depth discrimination. Last
but not least, when a structure is subjected to load, these techniques can be used in order to monitor the irreversible
damage phenomena, as manifested by the local heat accumulation in the vicinity of the defect. This eliminates the need
for external heat source, as any cyclic loading can induce the heat gradient necessary to pinpoint the defect accumulation
and propagation.
In the aforementioned context, lock-in thermography has been employed to monitor the delamination propagation in
composites and the critical failure of bonded repairs when the materials are subjected to fatigue loading. Lock-in
thermography proved successful in identifying debonding initiation and propagation as well in depicting the
thermoelastic stress field around purposely induced discontinuities.
Detection of surface breaking cracks using thermographic and non-contact ultrasonic methods
Show abstract
A combined ultrasound and thermography defect detection system using a raster scanned Q-switched laser as a source of
heat and ultrasound has been developed for identifying surface breaking defects. Heat is generated on a sample surface
by a laser source and the resultant thermal image is examined by a thermal imaging camera. This can be done using a cw
or a pulsed laser, but for ultrasonic generation a pulsed laser beam is required. When a defect is present, the flow of heat
in the sample is disturbed and a change in shape of the thermal spot on the sample's surface can be detected. The pulsed
laser beam generates simultaneously an ultrasonic wave that can be detected by a suitable transducer, which in this case
is an electromagnetic acoustic transducer (EMAT). The presence of a defect changes both the amplitude and frequency
content of the received wave. Three dimensional finite element modelling of the interaction between Lamb waves and
defects have been studied and compared with experimental data, in order to optimise source and detector positions
around a defect. The approach can detect surface crack defects via the ultrasonic and thermography method in one
measurement.
Feasibility of using line scanning thermography in NDE of wind turbine blades
Show abstract
Today, the increasing energy demand and the need for clean power generation has lead to the
improvement of wind turbines and the development non invasive inspection techniques for the
assessment of wind turbine blades to maintain long term reliability as well as to avoid catastrophic
failures.
Given the complexity of the geometry, the material composition and material thicknesses, finding a
NDT technique to effectively and rapidly inspect the blades is a challenging task. Wind turbine
blades are fabricated using different materials like fiber glass, carbon composites, foam and/ or balsa
wood. Layers of these materials are bonded together using an epoxy type resin. Inspection of the
bond quality between external layers and structural elements of the blade is of fundamental
importance for quality control and service of the blade.
In this study our efforts towards the applications of Line Scanning Thermography (LST) for the
analysis of test coupons fabricated using the materials employed in the manufacture of wind turbine
blades, as well as some wind turbine blade sections. LST utilizes a line heat source to thermally
excite the surface to be inspected and an infrared detector to record the transient surface temperature
variation produced by disbonds, and other subsurface imperfections. The LST technique has
provided a quick and efficient methodology to scan large composite structures, which makes it
desirable for the inspection of wind turbine blades. The scanning protocols developed for the
detection of sub-surface disbonds (delamination) in coupons and parts will be presented. The
successes and limitations of the technique will be discussed.
Nondestructive vision-based approaches for condition assessment of structures
Show abstract
Nondestructive evaluation techniques, including the use of optical instrumentation (e.g., digital cameras), image
processing and computer vision are promising approaches for structural health monitoring to complement sensorbased
approaches. This study applies and evaluates the underlying technical elements for the development of
an integrated inspection tool that is based on the use of commercially available digital cameras. The proposed
system can help an inspector to visually assess a target structure remotely, without the need of having to travel
to the bridge site, and by bypassing needed traffic detouring. Also, a contact-less vision-based crack detection
methodology is introduced and evaluated. Illustrative examples are provided to demonstrate the capabilities as
well as the limitations of the proposed vision-based approaches.
Model updating and prognosis of acoustic emission data in compact test specimens under cyclic loading
Show abstract
Acoustic emission (AE) is generated when cracks develop and it is used as an indicator of the current state of
damage in structural elements. Algorithms that use AE data to predict the state of a structural element are still in
their research stages because the relationship between crack length and AE activity is not well understood. The
process of trying to predict the future stage of a crack based on AE data is usually performed by an expert, and
requires significant experience. This paper proposes a new strategy for the use of AE data for structural prognosis.
A probabilistic model is used to predict AE data. An expert can analyze this data to draw conclusions about the
health of the structural member. The goal is to aid the analyst by providing an estimation of the AE activity in the
future. The methodology provides the cumulative signal strength at a future number of cycles, assuming the loading
and boundary conditions hold. The methodology uses a relationship between the rate of change of the cumulative
absolute energy of the AE with respect to the number of cycles and the stress intensity range. A third order
polynomial equation that describes the stress intensity range as function of the AE data is proposed. The variables
to be updated are treated as random and their joint probability distribution is computed using Bayesian inference.
Markov Chain Monte Carlo (MCMC) is used to forecast the cumulative signal strength at some number of cycles in
the future. The methodology is tested using a compact test specimen tested in structures lab at the University of
South Carolina.
NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems III
ANDERS: future of concrete bridge deck evaluation and rehabilitation
Show abstract
The Automated Nondestructive Evaluation and Rehabilitation System (ANDERS) aims to provide a uniquely
comprehensive tool that will transform the manner in which bridge decks are assessed and rehabilitated. It is going to be
achieved through: 1) much higher evaluation detail and comprehensiveness of detection at an early stage deterioration,
2) comprehensive condition and structural assessment at all stages of deterioration, and 3) integrated assessment and
rehabilitation that will be minimally invasive, rapid and cost effective. ANDERS is composed of four systems. that
merge novel imaging and NDE techniques, together with novel intervention approaches to arrest the deterioration
processes. These technologies are incorporated within a series of human-operated and robotic vehicles. To perform
assessments, ANDERS will be equipped with two complimentary nondestructive approaches. The first, Multi-Modal
Nondestructive Evaluation (MM-NDE) System aims to identify and characterize localized deterioration with a high
degree of resolution. The second, Global Structural Assessment (GSA) System aims to capture global structural
characteristics and identify any appreciable effects of deterioration on a bridge structure. Output from these two
approaches will be merged through a novel Automated Structural Identification (Auto St-Id) approach that will
construct, calibrate, and utilize simulation models to assess overall structural vulnerability and capacity. These three
systems comprise the assessment suite of ANDERS and will directly inform the Nondestructive Rehabilitation (NDR)
System. The NDR System leverages robotics for the precision and rapid delivery of novel materials capable of halting
the early-stage deterioration identified.
Rapid impact testing for quantitative assessment of large populations of bridges
Show abstract
Although the widely acknowledged shortcomings of visual inspection have fueled significant advances in the areas of
non-destructive evaluation and structural health monitoring (SHM) over the last several decades, the actual practice of
bridge assessment has remained largely unchanged. The authors believe the lack of adoption, especially of SHM
technologies, is related to the 'single structure' scenarios that drive most research. To overcome this, the authors have
developed a concept for a rapid single-input, multiple-output (SIMO) impact testing device that will be capable of
capturing modal parameters and estimating flexibility/deflection basins of common highway bridges during routine
inspections. The device is composed of a trailer-mounted impact source (capable of delivering a 50 kip impact) and
retractable sensor arms, and will be controlled by an automated data acquisition, processing and modal parameter
estimation software. The research presented in this paper covers (a) the theoretical basis for SISO, SIMO and MIMO
impact testing to estimate flexibility, (b) proof of concept numerical studies using a finite element model, and (c) a pilot
implementation on an operating highway bridge. Results indicate that the proposed approach can estimate modal
flexibility within a few percent of static flexibility; however, the estimated modal flexibility matrix is only reliable for
the substructures associated with the various SIMO tests. To overcome this shortcoming, a modal 'stitching' approach
for substructure integration to estimate the full Eigen vector matrix is developed, and preliminary results of these
methods are also presented.
Determination of chloride ion concentration in concrete by means of near infra-red spectroscopy
Show abstract
Concentration of chloride ions was determined with a classical chemical titration method in three types of
samples: a cracked concrete core and an undamaged concrete core, both taken from a bridge in Iowa, and
also from concrete test samples prepared at Rutgers University. Chloride concentration profiles were
obtained. The same samples were the subjected to the near infrared spectrometric determinations of
chloride content by two manufacturers of spectrometric instruments. Very good correlation between the
chemical and spectrometric measurements was obtained [ R2> 0.96], thus opening the possibility of rapid
on-site chloride concentration determination in concrete structures.
Recent advances in the development of a self-powered wireless sensor network for structural health prognosis
Show abstract
This paper presents the most recent advances in the development of a self powered wireless sensor network for steel and
concrete bridges monitoring and prognosis. This five-year cross-disciplinary project includes development and
deployment of a 4-channel acoustic emission wireless node powered by structural vibration and wind energy harvesting
modules. In order to accomplish this ambitious goal, the project includes a series of tasks that encompassed a variety of
developments such as ultra low power AE systems, energy harvester hardware and especial sensors for passive and
active acoustic wave detection. Key studies on acoustic emission produced by corrosion on reinforced concrete and by
crack propagation on steel components to develop diagnosis tools and models for bridge prognosis are also a part of the
project activities. It is important to mention that the impact of this project extends beyond the area of bridge health
monitoring. Several wireless prototype nodes have been already requested for applications on offshore oil platforms,
composite ships, combat deployable bridges and wind turbines. This project was awarded to a joint venture formed by
Mistras Group Inc, Virginia Tech, University of South Carolina and University of Miami and is sponsored through the
NIST-TIP Grant #70NANB9H007.
Piezoelectric power generation for civil infrastructure systems
Show abstract
Civil infrastructure systems (CIS) employ various small electronic components ranging from temperature and humidity
sensors used in buildings to acoustics emission sensors used for damage detection in bridges. Other than solar energy
that has already found several applications in CIS; moving loads, surface strain fluctuations, and wind energy available
in the vicinity of CIS constitute important sources of energy that can be converted into electricity. This paper focuses on
low power generation from these energy sources using piezoelectric transduction. Moving loads caused by travelling
vehicles can be used for exciting piezoceramics located on the road. Structural vibrations resulting from various sources
such as support motions and interaction of CIS with the surrounding fluid may yield local surface strain fluctuations.
Wind energy is available not only due to regular atmospheric flow but also due to the motion of vehicles travelling at
relatively high speeds. This paper investigates and formulates (1) the electromechanical moving load problem for slender
bridges with a piezoelectric cantilever and with embedded piezoceramics, (2) the problem of piezoelectric power
generation from surface strain fluctuations using a piezoceramic patch, and (3) piezoelectric energy harvesting from
wind excitation through aeroelastic flutter.
Adaptation of PWAS transducers to acoustic emission sensors
Show abstract
Piezoelectric wafer active sensors (PWAS) are non-intrusive transducers that can convert
mechanical energy into electrical energy, and vice versa. They are well known for their dual use as either
actuators or sensors. Though PWAS has shown great potential for active sensing, its capability for
acoustic emission (AE) detection has not yet been exploited. In the reported work, we have explored the
implementation of PWAS transducers for both passive (AE sensors) and active (in-situ ultrasonic
transducers) sensing using a single PWAS network. The objective of the work presented in this paper is to
adapt PWAS as AE sensors and compare it to the commercially available AE transducers such as PAC
R15.
An experiment has been designed to show how PWAS can be used for AE detection and the results
were compared to a standard AE sensor, PAC R15I. Tests on compact tension specimens have also been
conducted to show PWAS capability to pick up AE events during fatigue loading. PWAS field
installation technology has been tested with packaging similar to that used for traditional strain gauges.
The performance of packaged PWAS has been compared with that of conventional AE transducers R15I.
We have found that PWAS not only can detect the presence of AE events but also can provide a wide
frequency bandwidth. At this stage, PWAS underperforms the commercial AE sensors. To make PWAS
ready for field test, signal to noise ratio needs to be significantly improved.
NIST Technology Innovation Program on Civil Infrastructure Critical National Need: Advanced Sensing Technologies for the Infrastructure: Bridges, Roads, Highways, and Water Systems IV
Lessons from two field tests on pipeline damage detection using acceleration measurement
Show abstract
Early detection of pipeline damages has been highlighted in water supply industry. Water pressure change in pipeline
due to a sudden rupture causes pipe to vibrate and the pressure change propagates through the pipeline. From the
measurement of pipe vibration the rupture can be detected. In this paper, the field test results and observations are
provided for implementing next generation of SCADA system for pipeline rupture detection. Two field tests were
performed on real buried plastic and metal pipelines for rupture detection. The rupture was simulated by introducing
sudden water pressure drop caused by water blow-off and valve control. The measured acceleration data at the pipe
surfaces were analyzed in both time and frequency domain. In time domain, the sudden narrow increase of acceleration
amplitude was used as an indication of rupture event. For the frequency domain analysis, correlation function and the
short time Fourier Transform technique were adopted to trace the dominant frequency shift. The success of rupture
detection was found to be dependent on several factors. From the frequency analysis, the dominant frequency of metal
water pipe was shifted by the water pressure drop, however, it was hard to identify from the plastic pipeline. Also the
influence of existing facility such as airvac on pipe vibrations was observed. Finally, several critical lessons learned in
the viewpoint of field measurement are discussed in this paper.
Experimental and analytical study of water pipe's rupture for damage identification purposes
Show abstract
A malfunction, local damage or sudden pipe break of a pipeline system can trigger significant flow variations. As shown
in the paper, pressure variations and pipe vibrations are two strongly correlated parameters. A sudden change in the flow
velocity and pressure of a pipeline system can induce pipe vibrations. Thus, based on acceleration data, a rapid detection
and localization of a possible damage may be carried out by inexpensive, nonintrusive monitoring techniques. To
illustrate this approach, an experiment on a single pipe was conducted in the laboratory. Pressure gauges and
accelerometers were installed and their correlation was checked during an artificially created transient flow. The
experimental findings validated the correlation between the parameters. The interaction between pressure variations and
pipe vibrations was also theoretically justified. The developed analytical model explains the connection among flow
pressure, velocity, pressure wave propagation and pipe vibration. The proposed method provides a rapid, efficient and
practical way to identify and locate sudden failures of a pipeline system and sets firm foundations for the development
and implementation of an advanced, new generation Supervisory Control and Data Acquisition (SCADA) system for
continuous health monitoring of pipe networks.
Smart wireless sensor system for lifeline health monitoring under a disaster event
Show abstract
This paper discusses issues of using wireless sensor systems to monitor structures and pipelines in the case of disastrous
events. The platforms are deployed and monitored remotely on lifetime systems, such as underground water pipelines. Although
similar systems have been proposed for monitoring seismic events and the structure health of bridges and buildings,
several fundamental differences necessitate adaptation or redesign of the module. Specifically, rupture detection in water
delivery networks must respond to higher frequency and wider bandwidth than those used in the monitoring of seismic
events, structures, or bridges. The monitoring and detection algorithms can also impose a wide range of requirements on
the fidelity of the acquired data and the flexibility of wireless communication technologies. We employ a non-invasive
methodology based on MEMS accelerometers to identify the damage location and to estimate the extent of the damage.
The key issues are low-noise power supply, noise floor of sensors, higher sampling rate, and the relationship among displacement,
frequency, and acceleration.
Based on the mentioned methodology, PipeTECT, a smart wireless sensor platform was developed. The platform was
validated on a bench-scale uniaxial shake table, a small-scale water pipe network, and portions of several regional water
supply networks. The laboratory evaluation and the results obtained from a preliminary field deployment show that such
key factors in the implementation are crucial to ensure high fidelity of the acquired data. This is expected to be helpful in
the understanding of lifeline infrastructure behavior under disastrous events.
Mitigation of the consequence of seismically induced damage on a utility water network by means of next generation SCADA
Show abstract
When a lifeline system such as a water delivery network is damaged due to a severe earthquake, it is critical to
identify its location and extent of the damage in real time in order to minimize the potentially disastrous
consequence such damage could otherwise entail. This paper demonstrates how the degree of such minimization
can be estimated qualitatively by using the water delivery system of Irvine Water Ranch District (IRWD) as testbed,
when it is subjected to magnitude 6.6 San Joaquin Hills Earthquake. In this demonstration, we consider two
cases when the IRWD system is equipped or not equipped with a next generation SCADA which consists of a
network of MEMS acceleration sensors densely populated and optimally located. These sensors are capable of
identifying the location and extent of the damage as well as transmitting the data to the SCADA center for
monitoring and control.
An automated repair method of water pipe infrastructure using carbon fiber bundles
Sean Wisotzkey,
Heath Carr,
Ed Fyfe
Show abstract
The United States water pipe infrastructure is made up of over 2 million miles of pipe. Due to age and deterioration, a
large portion of this pipe is in need of repair to prevent catastrophic failures. Current repair methods generally involve
intrusive techniques that can be time consuming and costly, but also can cause major societal impacts. A new automated
repair method incorporating innovative carbon fiber technology is in development. This automated method would
eliminate the need for trenching and would vastly cut time and labor costs, providing a much more economical pipe
repair solution.
Development of a frequency-tunable optical phase lock loop (OPLL) for high resolution fiber optic distributed sensing
Show abstract
We report on the development of a precision-tunable, dual wavelength, optical light source suitable for high
performance fiber optic Brillouin scattering distributed sensing. The design is based on an Optical Phase Locked Loop
(OPLL) system using novel narrow linewidth, low frequency noise and high stability PLANEX external cavity
semiconductor. The inherent wavelength stability of PLANEX lasers (typically an order of magnitude better that any
DFB laser on the market) enable the OPLL to operate continuously over a wide ambient temperature range without
degradation in wavelength locking performance. The OPLL architecture is implemented with polarization maintaining
(PM) components and has a very low beat frequency jitter on the order of few kHz. The OPLL frequency tuning range
is between 8 and 14 GHz, with fast tuning of sweep steps on the order of 100 μsec. Such a frequency tuning range
covers practically all corresponding temperature and strain sensing applications based on the measurement of the
frequency shift produced by spontaneous or stimulated Brillouin scattering, and thus is a versatile and enabling
technology for both BOTDA/BOTDR distributed sensing systems.
Remote monitoring and prognosis of fatigue cracking in steel bridges with acoustic emission
Show abstract
Acoustic emission (AE) monitoring is desirable to nondestructively detect fatigue damage in steel bridges. Investigations
of the relationship between AE signals and crack growth behavior are of paramount importance prior to the widespread
application of passive piezoelectric sensing for monitoring of fatigue crack propagation in steel bridges. Tests have been
performed to detect AE from fatigue cracks in A572G50 steel. Noise induced AE signals were filtered based on friction
emission tests, loading pattern, and a combined approach involving Swansong II filters and investigation of waveforms.
The filtering methods based on friction emission tests and load pattern are of interest to the field evaluation using sparse
datasets. The combined approach is suitable for data filtering and interpretation of actual field tests. The pattern
recognition program NOESIS (Envirocoustics) was utilized for the evaluation of AE data quality. AE parameters are
associated with crack length, crack growth rate, maximum stress intensity and stress intensity range. It is shown that AE
hits, counts, absolute energy, and signal strength are able to provide warnings at the critical cracking level where
cracking progresses from stage II (stable propagation) to stage III (unstable propagation which may result in failure).
Absolute energy rate and signal strength rate may be better than count rate to assess the remaining fatigue life of inservice
steel bridges.
Detection of active corrosion in reinforced and prestressed concrete: overview of NIST TIP project
M. A Gonzalez-Nunez,
A. Nanni,
F. Matta,
et al.
Show abstract
The US transportation infrastructure has been receiving intensive public and private attention in recent years. The
Federal Highway Administration estimates that 42 percent of the nearly 600,000 bridges in the Unites States are in need
of structural or functional rehabilitation1. Corrosion of reinforcement steel is the main durability issue for reinforced and
prestressed concrete structures, especially in coastal areas and in regions where de-icing salts are regularly used.
Acoustic Emission (AE) has proved to be a promising method for detecting corrosion in steel reinforced and prestressed
concrete members. This type of non-destructive test method primarily measures the magnitude of energy released within
a material when physically strained. The expansive ferrous byproducts resulting from corrosion induce pressure at the
steel-concrete interface, producing longitudinal and radial microcracks that can be detected by AE sensors. In the
experimental study presented herein, concrete block specimens with embedded steel reinforcing bars and strands were
tested under accelerated corrosion to relate the AE activity with the onset and propagation stages of corrosion. AE data
along with half cell potential measurements and galvanic current were recorded to examine the deterioration process.
Finally, the steel strands and bars were removed from the specimens, cleaned and weighed. The results were compared
vis-à-vis Faraday's law to correlate AE measurements with degree of corrosion in each block.
Wireless Sensor Network and Energy Harvesting
Embedded passive wireless sensors for detecting conductivity within RC structures
Show abstract
A passive, wireless and inexpensive sensor has been developed to monitor the conductivity of concrete and thereby
provide information on the progress of chloride-induced corrosion of the embedded reinforcement in concrete structures.
Sensors are designed to be attached to the reinforcement cages before placement of the concrete in new construction or
in portions of rehabilitated structures. Sensors will then be interrogated intermittently over the service life during routine
inspections. The results of two experimental investigations are discussed in this paper. In the first, conductivity sensors
were submerged in liquids of increasing conductivity. In the second, conductivity sensors were embedded in concrete
cylinders and interrogated over a 25-week period during initial set and curing of the concrete. Analysis of the measured
data shows that the passive conductivity sensors were successful in detecting a variety of conductivity levels in the
concrete.
Sensitivity analysis of transmissibility functions for structural damage detection
Show abstract
In order to assess structural safety conditions, many vibration-based damage detection methods have been developed in
recent years. Among these methods, transmissibility function analysis can utilize output data only, and proves to be
effective in damage detection. However, previous research mostly focused on experimental validation of using
transmissibility function for damage detection. Very few studies are devoted to analytically investigating its performance
for damage detection. In this paper, a spring-mass-damper model with multiple degrees-of-freedom is formulated for
further analytical studies on the damage sensitivity of transmissibility functions. The sensitivity of transmissibility
function against structural mass and stiffness change is analytically derived and validated by numerical examples.
Vibration-Based NDE Technologies
Utilization of strong motion data for damage assessment of reinforced concrete bridges
Show abstract
This study investigates the performance of a vibration-based technique for damage assessment of reinforced concrete
bridges from non-stationary and incomplete acceleration response measurements during high amplitude earthquakes. The
proposed damage assessment technique is targeted to be used in the aftermath of a major earthquake event to rapidly and
remotely assess the functionality status of the bridge and identify potential hazards to the public safety. As the first step
of the procedure, time-frequency representation of the response of the bridge is achieved by applying stochastic subspace
system identification technique to successive and overlapping windows of the response measurements. The timefrequency
representation is then used to identify the longest ending segment of the response with relatively stable modal
properties. Post-earthquake experimental modal properties of the bridge are subsequently extracted from the identified
stable portion of the response. These properties are used to estimate the amount of degradation in stiffness of the
structural elements through an optimization-based finite element model updating technique. The Genetic Algorithm
optimization technique is used to update the stiffness properties of the structural elements by minimizing the error
between analytical and experimental modal properties of the bridge. The proposed damage assessment procedure is
applied to experimental data from a large-scale shake table test during which a quarter-scale model of a reinforced
concrete bridge was subjected to a series of earthquake and low-amplitude white noise base excitations. The meaningful
agreement between the stiffness correction factors identified from both types of motions at the same damage state of the
bridge demonstrates that the proposed procedure can effectively be applied for post-earthquake damage assessment of
the bridges from nonlinear responses during high amplitude earthquakes.
Modal parameter identification of civil engineering structures under operational conditions
Show abstract
This paper deals with the realization of finite dimensional, linear, time-invariant models of structural systems in
the state space description from the response (output) of the system. The theory and and underlying principles
of two stochastic system identification algorithms are first described. The applications of the algorithms to
two civil engineering structures follow the theory. Ambient vibration data collected from a building and a
bridge, both are permanently instrumented by accelerometer networks, are used to derive the models. The
vibration characteristics, i.e., the frequencies, damping ratios, and associated mode shapes, of the structures are
then retrieved from the models. The stochastic system identification algorithms prove to be very effective in
identifying the vibration characteristics of the structures.
Alternative determination of cable forces using flexural theory of axially loaded member
Show abstract
In this study, a back calculation formula using frequencies of two arbitrary modes of vibration is proposed to compute
the tension force in pre-stressed members. Derivation of the proposed formula is based on the vibration theory of an
axially loaded flexural member. This paper describes the use of the proposed formula to successfully recover the tension
forces of lab-controlled pre-stressing strands. Data of field tests confirm that the proposed formula is also capable of
predicting cable forces of a cable-stay bridge in good agreement with those obtained from traditional first frequency
calculation and those by in-situ instrumentation with errors within acceptable range. As a result, it is concluded that such
calculation can also be practically useful in giving reference values for other main effective methods regardless that
reliable values of the first frequency of lateral vibration is available or not.
Monitoring vibration-based structural health using nonlinear approach
W. Punurai,
T. Chanpheng,
T. Sookjit
Show abstract
This paper presents a method for determining the degree of nonlinearity (DON) from the structural vibration data for
monitoring the change in health of structures. Using Hilbert Transform of the frequency response function, the DON
measures the nonlinearity present in the vibration response. It is shown that a plot of the DON against the magnitude of
the motion represents the behavior of a structure. If the structure is damaged during a new striking motion, the DON
parameter will deviate from its healthy signature. Data from numerical simulation and experimental measurement were
used to evaluate the proposed method.
Smart Materials Sensing Technologies
The improvement of accuracy of standalone GPS with an alternative positioning algorithm
Show abstract
Commercial standalone Global Positioning System (GPS) receivers suffer from multiple errors including multipath
bias and ionospheric signal disturbance, especially in urban environment where GPS signal can be easily
affected and altered. There are multiple techniques to solve this issue, yet every method has limitations and
certain problems. Furthermore, the positioning accuracy of the commercial low-cost GPS is very poor in urban
conditions, in most cases due to multi-path bias. In this paper, a novel method was proposed which introduced
certain parameters and weighted coefficients to the existing GPS positioning algorithm in order to compensate
the impact of multi-path and poor signal receptions. The measurement accuracy of the commercial GPS receiver
with existing algorithms and that of the new algorithm proposed have been studied simultaneously to determine
the improvement. Tests performed in Boston metropolitan area, using low-cost off-the-shelf equipment, show
that the new method yields over 50% accuracy improvements (RMS) and fewer fluctuations than conventional
algorithms implemented. These studies demonstrated that better accuracy could be achieved by considering the
relationship between multi-path bias and signal strength. The detailed analysis of applying different parameters
in various conditions with experiment results is presented in the paper.
On suitability of feature extraction techniques for local damage detection
Show abstract
Damage in the form of cracks near rivet holes in a steel channel section can be characterized by inspecting ultrasonic
signals containing valuable information about these anomalies.
Time-frequency representation (TFR) of time-history
signal is an effective way to extract damage features out of an ultrasonic signal scattered from cracks. Several techniques
are available to obtain Time-frequency representation and out of which feature extraction can be performed. However,
every technique has its own advantages and disadvantage which makes it cumbersome to ascertain which specific
technique is suitable to which specific problem. In present study, six TFR techniques e.g. Short Time Fourier Transform,
Continuous Wavelet Transform, Wigner-Ville Spectrum, Hilbert-Huang Transform, Williams-Choi Transform and Stransform
have been used to extract feature out of time-history signal obtained from finite element based wave scattering
simulation of a plate with and without cracks near the rivet holes. Extracted damage features have been used to quantify
the damage as a unique value by defining damage index formulation. Further, a comparison study has been carried out to
assess these six techniques for their ability to give effective, reliable and consistent information about the cracks. Matlab
codes have been developed to perform feature extraction and damage index calculation.
A high temperature piezoelectric sensor for structure health monitoring
Show abstract
High temperature sensors play a significant role in aerospace, automotive and energy industries. In this paper, a shearmode
piezoelectric accelerometer using YCa4O(BO3)3 single crystals (YCOB) was designed and fabricated for high
temperature sensing applications. The prototype sensor was tested at the temperature ranging from room temperature to
1000°C. The sensitivity of the sensor was found to be 1.9±04 pC/g throughout the tested frequency and temperature
range. Moreover, YCOB piezoelectric accelerometers remained stable performance at 1000°C for a dwell time of three
hours.
Fatigue crack detection in thick steel structures with piezoelectric wafer active sensors
Show abstract
This paper presents a set of numerical and experimental results on the use of guided waves for structural health
monitoring (SHM) of crack growth during a fatigue test in a thick steel plate used for civil engineering application. The
capability of embedded piezoelectric wafer active sensors (PWAS) to perform in situ nondestructive evaluation (NDE) is
explored. Numerical simulation and experimental tests are used to prove that PWAS can perform active SHM using
guided wave pitch-catch method and passive SHM using acoustic emission (AE). Multi-physics finite element (MPFEM)
codes are used to simulate the transmission and reception of guided waves in a 1-mm plate and their diffraction by
a through hole. The MP-FEM approach permitted that the input and output variables be expressed directly in electric
terms while the two-ways electromechanical conversion was done internally in the MP-FEM formulation. The analysis
was repeated for several hole sizes and a damage index performances was tested. AE simulation was performed with the
MP-FEM approach in a 13-mm plate in the shape of the compact tension (CT) fracture mechanics specimen. The AE
event was simulated as a pulse of defined duration and amplitude. The electrical signal measured at a receiver PWAS
was simulated. Daubechies wavelet transform was used to process the signal and identify its Lamb modes and FFT
frequency contents. Experimental tests were performed with PWAS transducers acting as passive receivers of AE
signals. The 8-mm thick flange of an I beam was instrumented on one side with PWAS transducers and on the other side
with conventional AE transducers (PAC R15I) acting as comparison witnesses. An AE source was simulated using 0.5-
mm pencil lead breaks; the PWAS transducers were able to pick up AE signal with good strength. Subsequently, PWAS
transducers and R15I sensors were applied to a 13-mm CT specimen subjected to accelerated fatigue testing. The PWAS
and R15I transducers signals were collected with PAC data acquisition system using the AE-win software. Comparative
results of AE hits and source localization from the PWAS and R15I sensors are given. Active sensing in pitch catch
mode was applied between the PWAS transducers installed on the CT specimen and damage indexes were calculated and
correlated with physical crack growth as measured optically. The paper finishes with summary, conclusion, and
suggestions for further work.
Poster Session
Utilization of ultrasonic guided waves to detect delamination in aviation industries
Show abstract
Composite materials in comparison with metals have many advantages such as high strength and corrosion resistance,
therefore are strongly used in fields of civil and military applications. However, defects such as delamination, fiber
cracking, fiber and matrix separation and the like are more critical than steel structures. As a result, the use of accurate
and cost-effective method for monitoring of composite structures is very important. In this regard, using ultrasonic
guided wave is growing rapidly in many industries which is because of guided wave's characteristics such as their high
sensitivity to defects, ability to propagate in large range as well as some other practical points. In this paper, after
introducing ultrasonic guided waves, accessing the features of the signal produced due to the delamination in a fiberglass
plate is discussed. Subsequently, utilization of piezoelectric probe of guided wave and its measurement will be
elaborated. Last stage of this study will discusses analysis of signals received under assortment of conditions in the
measurement process, upon which, a systematic approach in delamination detection will be introduced.
Long-term monitoring and field testing of an innovative multistory timber building
Show abstract
An innovative three-story timber building, using self-centering, post-tensioned timber shear walls as the main horizontal
load resisting system and lightweight composite timber-concrete floors, has recently been completed in Nelson, New
Zealand. It is expected to be the trailblazer for similar but taller structures to be more widely adopted. Performance based
standards require an advanced understanding of building responses and in order to meet the need for in-situ performance
data the building has been subjected to forced vibration testing and instrumented for continuous monitoring using a total
of about 90 data channels to capture its dynamic and long-term responses. The first part of the paper presents a brief
discussion of the existing research on the seismic performance of timber frame buildings and footfall induced floor
vibrations. An outline of the building structural system, focusing on the novel design solutions, is then discussed. This is
followed by the description of the monitoring system. The paper emphasizes the need for optimal placement of a limited
number of sensors and demonstrates how this was achieved for monitoring floor vibrations with the help of the effective
independence-driving point residue (EfI-DPR) technique. A novel approach to the EfI-DPR method proposed here uses a
combinatorial search algorithm that increases the chances of obtaining the globally optimal solution. Finally, the results
from the forced vibration tests conducted on the whole building at different construction stages are reviewed.
Galloping comparative analysis for transient main cables of suspension bridge during construction
Show abstract
The cross-sectional shapes of two construction projects for the transient main cables are non-circular
cross-sections during construction of the long-span suspension bridge, so the transient main cables can experience
galloping instabilities. The galloping coefficients of the several representative cases of two construction projects for the
transient main cables without wind-resistant measures for the long-span suspension bridge were investigated for the first
time by means of the CFD method, referring to an erecting suspension bridge. Results show that for the project 1, at the
early stages of the main cables construction, the galloping instabilities can occur, but at the later stages of that, the
galloping instabilities cannot occur. For the project 2, there exists a lot of wind attack angles whose galloping
coefficients are less than 0 at the whole construction stages. From the perspective for galloping instability the project 1
is better 2.Through the analysis and comparison the galloping performance of two kinds of construction projects for the
transient main cables, the advantage and disadvantage for two construction projects is explained theoretically from the
perspective for whether can result in the galloping instability.
Pipe performance analysis with nonparametric regression
Show abstract
Asbestos cement (AC) water mains were installed extensively in North America, Europe, and Australia during
1920s-1980s and subject to a high breakage rate in recent years in some utilities. It is essential to understand
how the influential factors contribute to the degradation and failure of AC pipes. The historical failure data
collected from twenty utilities are used in this study to explore the correlation between pipe condition and its
working environment.
In this paper, we applied four nonparametric regression methods to model the relationship between pipe
failure represented by average break rates and influential variables including pipe age and internal and external
working environmental parameters. The nonparametric regression models do not take a predetermined form
but it needs information derived from data. The feasibility of using a nonparametric regression model for the
condition assessment of AC pipes is investigated and understood.
MIMO array imaging for ultrasonic nondestructive testing
Show abstract
Ultrasonic sensor arrays continue to be broadly applied for nondestructive material testing. Generally, conventional
beamforming techniques have been the favorite approach to generate images from the sensor array data. In this paper,
we examine the use of multiple-input multiple-output (MIMO) ultrasonic processing technique for imaging internal
structures of materials. The goal is to identify and locate potential defects and anomalies. The imaging technique is
comprised of excitation of transmitting sensors with sequential or orthogonal wideband signals, matched filtering, and
adaptive weighting. The weighting of the signals at the receiver takes into account the transducer ultrasound radiation
patterns. The MIMO technique is particularly attractive for ultrasonic imaging, as the different bistatic combinations of
transmit and receive sensor pairs allows effective and simple formations of virtual arrays with extended apertures and
denser spatial sampling. As such, high-resolution images can be generated with fewer or available transducers. The
performance of this technique is experimentally examined using test specimens with artificially drilled small size flat
bottom holes that simulate defects. One-dimensional and two-dimensional array configurations are used to form desired
virtual arrays and their respective imaging capabilities are evaluated and compared.
Detection of sub-surface crack in railway wheel using a new sensing system
S. J. Kwon,
J. W. Seo,
D. H. Lee,
et al.
Show abstract
To evaluate wheel defect, it is necessary to develop a new NDT on railway wheel. Unlikely a conventional NDT system,
the NDT system of the present paper can detect a sub-surface crack. In the present paper, the new NDT method is
applied to the detection of surface and sub-surface crack defects for railway wheels. To detect the defects for railway
wheels, the sensor for new NDT is optimized and the tests are carried out with respect to sub-surface defects respectively.
The result shows that the surface crack as well as sub-surface crack could be detected by using new NDT method.
Inspection of corrosion in carbody and under frame for rolling stocks using pulsed eddy current testing
Show abstract
Under frame side sill and carbody of rolling stock structures are designed for preventing corrosion in order to meet
mechanical requirements. However during long operation time more than 30 years, there are corrosion in the under
frame side sill caused by environmental effect, vibration and etc. So, detection and evaluation of the corrosion in the
under frame nondestructive is one of important and extending their life time. So, in this study, we have investigated
performance of pulsed eddy current testing method by measuring thickness variation of fabricate of carbody and under
frame for rolling stocks. And then, the process of evaluating remaining life according to testing of corrosion amount is
introduced.
Mechanical degradation of cross-ply laminates monitored by acoustic emission
Show abstract
This study deals with the investigation of cross ply composites failure by acoustic emission (AE). Broadband AE sensors
monitor the different sources of failure in coupons of this material during a tensile loading-unloading test. The
cumulative number of AE activity, and other qualitative indices based on the shape of the waves, were well correlated to
the sustained load. AE parameters indicate the shift of failure mechanisms within the composite as the load increases.
The ultimate goal is a methodology based on NDT techniques for real time characterization of the degradation and
identification of the fracture stage of advanced composite materials.
Development of a C-Scan phased array ultrasonic imaging system using a 64-element 35MHz transducer
Show abstract
Phased array imaging systems provide the features of electronic beam steering and dynamic depth focusing that cannot
be obtained with conventional linear array systems. This paper presents a system design of a digital ultrasonic imaging
system, which is capable of handling a 64-element 35MHz center frequency phased array transducer. The system
consists of 5 parts: an analog front-end, a data digitizer, a DSP based beamformer, a computer controlled motorized
linear stage, and a computer for post image processing and visualization. Using a motorized linear stage, C-scan images,
parallel to the surface of scanned objects may be generated. This digital ultrasonic imaging system in combination a 35
MHz phased array appears to be a promising tool for NDT applications with high spatial resolution. It may also serve as
an excellent research platform for high frequency phased array design and testing as well as ultrasonic array signal
algorithm developing using system's raw RF data acquisition function.
Static test of the embedded fiber Bragg gratings composite wind turbine blades
Show abstract
Wind power is non-pollution energy. Wind energy is getting more attentions when the energy problems come out.
Blades are the most critical parts in the wind turbine, so it's very important to do research on the wind turbine blades. In
this paper, 300W small wind turbine blades are used for test analysis. The test is based on structural analysis of the
blades and layout of the Bragg sensor (FBG) and strain gauges. The smart blade static load experiments were done on a
single point and multiple points load. The FBG sensors strain monitoring results shows the same strain distribution rule
as finite element simulation result, which confirmed that wind turbine blade structural health monitoring using FBG
sensor is feasible.
Assessment of PZT transducer bonding techniques under drop-weight impact loading in composites
Show abstract
This paper describes the robustness of a structural health monitoring system (SHM) that utilizes lead-zirconatetitanate
(PZT) transducers tested on carbon fibre composite coupons under drop-weight impact loading. Four PZT
transducers are attached to the surface of 10.16 cm x 15.24 cm aerospace grade carbon fibre coupons using four types
of adhesives: cyanoacrylate, epoxy, methyl methacrylate, and silicon. Each PZT transducer is tuned to excite
preferentially an A0 mode guided wave burst into each composite coupon prior to and following an impact. The
output from a PZT transducer, the amplitude of the propagating guided waves measured using a laser vibrometer on
the coupon surface and the RMS velocity is plotted. The cycle is repeated for the three remaining transducers. The
electrical admittance is also measured using an impedance analyzer prior to and following impact. This paper
illustrates how a robustness metric expressed in terms of admittance can be used to infer the ability of the SHM
system to generate guided waves and to detect damage following impact. The robustness metric is a measure of the
adhesive strength and the mechanism to provide accurate damage detection results. It is shown that transducers
attached using silicon provide accurate damage detection results based on pre-attached adhesive yielding difference
of <0.5% obtained from electrical admittance measurements before and after impact.
Physics-based classification of acoustic emission waveforms
Show abstract
The classification of acoustic emission source mechanisms based on features related to the physics of acoustic emission
signal generation is considered in this paper. Numerically generated acoustic emission waveforms are used for this
purpose. Conventional acoustic emission parameters such as rise-time, duration, and frequency content do not
effectively characterize acoustic emission waveforms for the purpose of identifying the source mechanisms. Features
unique to the different source mechanisms and relative positions of the sensor with respect to the source were identified
and extracted from numerically obtained acoustic emission waveforms. This feature selection appears to be successful in
capturing the differences related to the source mechanisms considered here. Correlation coefficients of the 45 features
with different waveforms were first obtained, and their principal components determined. The dominant principle
components were found to adequately characterize the waveforms and relate them to their source mechanisms. Better
than 90 percent success was seen when only the first two principle components were employed, even in noisy signals
considered here.
Residual capacity estimation of bridges using structural health monitoring data
Show abstract
In this study, a vibration-based procedure for residual capacity estimation of bridges after damaging earthquake events is
proposed. The procedure starts with estimation of collapse capacity of the intact bridge using incremental dynamic
analysis (IDA) curves. The collapse capacity is defined as the median intensity level of the earthquakes that cause global
or local collapse within the structure. A database of post-earthquake modal properties is created by calculating the
analytical modal properties of the bridge after each nonlinear response history analysis performed for generation IDA
curves. After the damaging event, experimental modal properties of the bridge are identified from vibration
measurements of the bridge. These properties along with the modal properties database are used to find ground motionintensity
pairs that can drive nonlinear FE model of the structure to the current damage state of the bridge. The IDA
curves corresponding to the damaged FE model of the bridge are subsequently used to estimate amount of loss in
collapse capacity of the damaged structure. Estimated loss in capacity of the bridge besides the bridge-site-specific
seismic hazard curves are used to update the functionality status of the bridge. Proposed procedure is applied to
experimental data from a large-scale shake table test on a quarter-scale model of a short-span reinforced concrete bridge.
The bridge was subjected to a series of earthquake ground motions introducing progressive seismic damage to the bridge
which finally led to the failure of one of the bents. Residual collapse capacity and functionality status of the bridge are
updated at different stages of the experiment using the proposed procedure.
Laser ultrasound technique for material characterization of Zircaloy cladding tubes in elevated temperature environment
Cheng-Hung Yeh,
Che-Hua Yang
Show abstract
This research focuses on characterizing elastic properties of Zircaloy cladding tubes at high temperature
environment up to 295°C. A laser ultrasound technique (LUT) is used to measure the dispersions of guided waves
propagating along the axial direction of the cladding tubes at different temperature environment. It is shown that the
LUT is able to measure the dispersion curve of Zircaloy in the elevated temperature environment. Then an inversion
procedure is used to determine elastic constants of the Zircaloy tubes at high temperature from the measured dispersion
spectra of guided waves. The dispersion spectra shift towards the direction of lower frequency and lower velocity while
the temperature increase. The Young's modulus is found to decrease linearly as the temperature increasing. This method
is potentially useful to probe the material properties at high temperature environment in a remote and nondestructive way
which is desired in nuclear power industry.
Laser ultrasound technique for ray tracing investigation of Lamb wave tomography
Show abstract
This paper presents a method for Lamb wave tomography utilizing a quantitative laser ultrasound visualization
technique. Lamb wave tomography had been made for image restructuring of the defect region information of specimen,
including position, size and shape. Previous researches developed existing algorithm to restructure image in Lamb wave
tomography. However these restructured algorithms are susceptible to refraction, strong scattering or abrupt change in
the thickness and result inaccurate image reconstruction. This paper employs experimental method named offset grid
scan for Lamb wave propagating along samples and extracts the group velocity of Lamb wave using π -point phase
comparison signal processing. The goal of the offset grid scan in a very short temporal domain presented in this study is
to counteract the above problem lead to various errors. In this research, the experimental method with the numerical
results is more accurate than previous algorithms.
Fabrication of 1-3 piezo-composites using new micro PZT fibers
Show abstract
This paper presents a novel fabrication method of PZT micro-fibers using activated carbon template with the aim of
manufacturing PZT/epoxy 1-3 composites. Porous carbon was first prepared by chemical activation technology. The pore
diameter formed in an activated carbon template is of several microns and lengths are up to several millimeters. These
pores provide a basic platform to grow PZT fibers inside. Then the carbon template is removed at high calcination
temperatures to form PZT micro-fibers. Subsequently, thermo-gravimetric analysis (TG) and differential scanning
calorimetry (DSC) were performed to analyze the process of removing the template as temperature changing. For
manufacturing 1-3 piezo-composites, the PZT fibers were carefully aligned in one direction and infiltrated by epoxy resin.
Based on the observation from X-ray diffraction (XRD) the fibers show a pure pervoskite phase at low sintering
temperature of 950°C. The fibers embedded orderly in the epoxy matrix are smoothly distributed and straightened which
were observed using a scanning electron microscopy (SEM). The diameter of fibers is around several microns with the
length up to a few millimeters, matching well with pores in the template. The new micro-fiber composite material can be
potentially used in a sensor with high directivity in structural health monitoring.
Application of anti-symmetric flexural modes for the detection of moisture
Po-Hsien Tung,
Che-Hua Yang
Show abstract
Anti-symmetric flexural (ASF) modes are anti-symmetric type of guided waves propagating along the tip of
wedge-shaped waveguides. While the wedge tips are coated a thin layer of hydroscopic film, the velocity of ASF mode
is sensitive the moisture through its contact with the film. This study presents a combined numerical experimental
investigation on the effects of moisture for the propagation behaviors of ASF modes. A laser ultrasound technique is
applied to measure dispersion spectra of ASF modes propagating along the wedge tips with hydroscopic film under
various humidity controlled by a chamber. Finite element simulations are used to simulate the effects of moisture on the
dispersion curves of the ASF modes.
A novel fatigue monitoring system utilizing bio-inspiration concept of data track of tree rings
Show abstract
The conventional analysis of fatigue damage accumulation based on the whole strain course has defects such as: high
cost, difficult to replace the strain sensors, complex system and unadaptable to engineering application et al. The data
track of tree rings links the fatigue monitoring and the bio-inspiration concept together. A counter based on Digital Signal
Processing (DSP) technology is adopted to record the realtime characteristic of fatigue behavior: the amplitude of strain,
the number of cycles and the stress state. Through the realization of the fatigue analysis algorithm by the DSP hardware
technique a novel fatigue monitoring system is developed. The data track of tree rings can definitely and increasingly
record the environmental characteristic of different environment growing condition, and this fatigue meter can record the
local fatigue course: the amplitude of strain, the number of cycles and the stress state. Thus, it is convenient to realize the
analysis of fatigue damage accumulation and give an early warning for structures.
Thermal protection system (TPS) monitoring using acoustic emission
Show abstract
This project investigates acoustic emission (AE) as a tool for monitoring the degradation of thermal protection systems
(TPS). The AE sensors are part of an array of instrumentation on an inductively coupled plasma (ICP) torch designed for
testing advanced thermal protection aerospace materials used for hypervelocity vehicles. AE are generated by stresses
within the material, propagate as elastic stress waves, and can be detected with sensitive instrumentation. Graphite
(POCO DFP-2) is used to study gas-surface interaction during degradation of thermal protection materials. The plasma is
produced by a RF magnetic field driven by a 30kW power supply at 3.5 MHz, which creates a noisy environment with
large spikes when powered on or off. AE are waveguided from source to sensor by a liquid-cooled copper probe used to
position the graphite sample in the plasma stream. Preliminary testing was used to set filters and thresholds on the AE
detection system (Physical Acoustics PCI-2) to minimize the impact of considerable operating noise. Testing results
show good correlation between AE data and testing environment, which dictates the physics and chemistry of the
thermal breakdown of the sample. Current efforts for the project are expanding the dataset and developing statistical
analysis tools. This study shows the potential of AE as a powerful tool for analysis of thermal protection material
thermal degradations with the unique capability of real-time, in-situ monitoring.
Combination of a GMR sensor and reconstruction algorithm: a novel magnetic sensing system
Show abstract
Over the past few years, the authors have developed a reconstruction algorithm that can accurately reconstruct
images of flaws from data obtained using conventional ECT sensors. The algorithm is simple and fast and
involves few steps, thus making it suitable for implementation on a PC. The algorithm can be applied to study
eddy current systems; it can also be used in conjunction with non-destructive testing methods involving a
magnetic field. However, there is one inherent limitation related to sensor design. In eddy current or magnetic
flux leakage, a conventional sensor is used to detect flaws in damaged areas. This sensor is designed in such
a manner that when the magnetic field is imposed on the target surface, the strength of the magnetic field is
maximized. This measurement method has remained unchanged since the introduction of the technique. The
developed reconstruction algorithm is designed for data obtained by imposing a uniform magnetic field on the
target surface. Recent developments in computer technology have enabled the integration of computing and
testing equipment; in this context, the authors believe that a new sensor for use with reconstruction algorithm
will be required. Therefore, the authors have developed a prototype sensor for applications to magnetic flux
leakage. The developed sensor comprises a GMR magnetic field sensor to detect a static magnetic field and two
magnets adjacent to the GMR sensor to magnetize the target specimen. The results of the combined use of the
sensor and the reconstruction algorithm are presented in this paper.
Live feed and variable snapshot recording of embedded magnetostrictive particulate sensors
Show abstract
This paper details an experiment using MSP, embedded into the matrix of carbon fiber beams, to locate predetermined
damage in each sample. The fabrication process of the composite samples and the development of the data acquisition
system used for this experiment are heavily detailed, including our method of implementing a live data feed with
variable "snapshot" recording. Also included are preliminary results from the experiment. These preliminary results
suggest credible flaws and lead to improvements in the fabrication process. This work identifies potential obstacles
when fabricating composites embedded with MSP and proposes possible solutions.
Research status on aerodynamic interference effects of wind-resistant performance of pylon
Show abstract
The aerodynamic interference effects of wind-resistant performance for pylon is one of very important problems in
numerical simulation studies of wind resistant of bridges. On the basis of looking through a great deal of related
literatures at home and abroad, research history, contents, method and achievements of the aerodynamic interference
effects are summarized, and the existing problem for galloping, buffeting and vortex-induced vibration of pylon and
directions for the next research are pointed out.
Feasibility research report of villa constructed of glass fiber reinforced concrete
Show abstract
With the development of economy and improvement degree of modernization, the villa project design
program tend to focus on the green, high-tech, humanities, and more emphasis on the integrity of space,
noble and elegant feeling. Therefore, based on the study of literatures, this paper discussed the present
situation and issue and features of Glass Fiber Reinforced Concrete and the feature of assembly house,
and confirmed that the villa of assemble house is feasible by built of Glass Fiber Reinforced Concrete.