In this study, wireless structural health monitoring (SHM) system of cable-stayed bridge is developed using Imote2-
platformed smart sensors. In order to achieve the objective, the following approaches are proposed. Firstly, vibrationand
impedance-based SHM methods suitable for the pylon-cable-deck system in cable-stayed bridge are briefly
described. Secondly, the multi-scale vibration-impedance sensor node on Imote2-platform is presented on the design of
hardware components and embedded software for vibration- and impedance-based SHM. In this approach, a solarpowered
energy harvesting is implemented for autonomous operation of the smart sensor node. Finally, the feasibility
and practicality of the multi-scale sensor system is experimentally evaluated on a real cable-stayed bridge, Hwamyung
Bridge in Korea. Successful level of wireless communication and solar-power supply for smart sensor nodes are verified.
Also, vibration and impedance responses measured from the target bridge which experiences various weather conditions
are examined for the robust long-term monitoring capability of the smart sensor system.
In this study, a multi-phase model update approach for system identification of real railway bridge using vibration test
results is present. First, a multi-phase system identification scheme designed on the basis of eigenvalue sensitivity
concept is proposed. Next, the proposed multi-phase approach is evaluated from field vibration tests on Wondongcheon
bridge which is a steel girder railway bridge located in Yangsan, South Korea. On the bridge, a few natural frequencies
and mode shapes are experimentally measured under the excitation of trains, ambient vibration and free vibration. The
corresponding modal parameters are numerically calculated from a three-dimensional finite element (FE) model which is
established for the target bridge. Eigenvalue sensitivities are analyzed for potential model-updating parameters of the FE
model. Then, structural subsystems are identified phase-by-phase using the proposed model update procedure. Based on
model update results, a baseline model of the Wondongcheon railway bridge is identified.
In this study, a technique using wireless impedance sensor node and interface washer is proposed to monitor prestressforce
in PSC girder bridges. In order to achieve the goal, the following approaches are implemented. Firstly, a wireless
impedance sensor node is designed for automated and cost-efficient prestress-force monitoring. Secondly, an
impedance-based algorithm is embedded in the wireless impedance sensor node for autonomous prestress-force
monitoring. Thirdly, a prestress-force monitoring technique using an interface washer is proposed to overcome
limitations of the wireless impedance sensor node such as measureable frequency ranges with narrow band. Finally, the
feasibility and applicability of the proposed technique are evaluated in a lab-scaled PSC girder model for which several
prestress-loss scenarios are experimentally monitored by the wireless impedance sensor node.
Acceleration and impedance signatures extracted from a structure are appealing features for a prompt diagnosis on
structural condition since those are relatively simple to measure and utilize. However, the feasibility of using them for
damage monitoring is limited when their changes go undisclosed due to uncertain temperature conditions, particularly
for large structures. In this study, temperature effect on hybrid damage monitoring of prestress concrete (PSC) girder
bridges is presented. In order to achieve the objective, the following approaches are implemented. Firstly, a hybrid
monitoring algorithm using acceleration and impedance signatures is proposed. The hybrid monitoring algorithm mainly
consists of three sequential phases: 1) the global occurrence of damage is alarmed by monitoring changes in acceleration
features, 2) the type of damage is identified as either prestress-loss or flexural stiffness-loss by identifying patterns of
impedance features, 3) the location and the extent of damage are estimated from damage index method using natural
frequency and mode shape changes. Secondly, changes in acceleration and impedance signatures were investigated under
various temperature conditions on a laboratory-scaled PSC girder model. Then the relationship between temperatures
and those signatures is analyzed to estimate and a set of empirical correlations that will be utilized for the damage
alarming and classification of PSC girder bridges. Finally, the feasibility of the proposed algorithm is evaluated by using
a lab-scaled PSC girder bridge for which acceleration and impedance signatures were measured for several damage
scenarios under uncertain temperature conditions.
In this study, a smart sensor node is developed for hybrid health monitoring of PSC girder bridges. Hybrid health
monitoring of those structures is to alarm damage occurrence, to classify damage-types, and to identify damage locations
and severities by measuring accelerations and impedance signals. In order to achieve the objective, the following
approaches are implemented. Firstly, a smart sensor node with wireless sensing capacity and embedded monitoring
algorithms is developed for measuring acceleration. Secondly, we design a hybrid damage monitoring scheme that
combines acceleration-based and impedance-based methods for PSC girder bridges. Finally, the performance of the
smart sensor node is evaluated using a laboratory-scale PSC girder bridge model for which acceleration and impedance
signals were measured for prestress-loss and stiffness-loss cases.
In this paper, a hybrid vibration-impedance approaches is newly proposed to detect the occurrence of damage, the
location of damage, and extent of damage in steel plate-girder bridges. Firstly, theoretical backgrounds of the hybrid
structural health monitoring are described. The hybrid scheme mainly consists of three sequential phases: 1) to alarm the
occurrence of damage in global manner, 2) to classify the alarmed damage into subsystems of the structure, and 3) to
estimate the classified damage in detail using methods suitable for the subsystems. Damage types of interest include
flexural stiffness-loss in girder and perturbation in supports. In the first phase, the global occurrence of damage is
alarmed by monitoring changes in acceleration features. In the second phase, the alarmed damage is classified into
subsystems by recognizing patterns of impedance features. In the final phase, the location and the extent of damage are
estimated by using modal strain energy-based damage index methods. The feasibility of the proposed system is evaluated
on a laboratory-scaled steel plate-girder bridge model for which hybrid vibration-impedance signatures were measured
for several damage scenarios.
Proc. SPIE. 6532, Health Monitoring of Structural and Biological Systems 2007
KEYWORDS: Ferroelectric materials, Safety, Detection and tracking algorithms, Sensors, Manufacturing, Nondestructive evaluation, Structural health monitoring, Damage detection, Bridges, Microsoft Foundation Class Library
To develop a promising hybrid structural health monitoring (SHM) system, which enables to detect damage by the
dynamic response of the entire structure and more accurately locate damage with denser sensor array, a combined use of
structural vibration and electro-mechanical (EM) impedance is proposed. The hybrid SHM system is designed to use
vibration characteristics as global index and EM impedance as local index. The proposed health-monitoring scheme is
implemented into prestressed concrete (PSC) girder bridges for which a series of damage scenarios are designed to
simulate various prestress-loss situations at which the target bridges can experience during their service life. The
measured experimental results, modal parameters and electro-magnetic impedance signatures, are carefully analyzed to
recognize the occurrence of damage and furthermore to indicate its location.
Guided wave techniques have been used for pipeline inspection because of their long-range inspection capability. One of
main concerns of these techniques is how ones decide axial interval of sensors. This question is related to the
characteristics of attenuation of cylindrical guided waves. Parametric density concept is proposed for a long-range
pipeline inspection. This concept is designed to obtain the attenuation of ultrasonic guided waves propagating in
underwater pipeline without complicated calculation of attenuation dispersion curves. For this study, three pipe materials
are considered, then different transporting fluids are assumed, and four different pipe geometries are adopted. It is shown
that the attenuation values based on the parametric density concept reasonably match with the attenuation values
obtained from the dispersion curves. However, it seems that the parametric concept is only applicable for fluid-filled
underwater pipes. The limitations of the parametric density concept are also discussed.
To develop a promising hybrid structural health monitoring system, which enables to detect damage by the dynamic response of the entire structure and more accurately locate damage with denser sensor array, a combined use of mechanical vibration and electro-mechanical impedance is proposed. For the verification of the proposed healthmonitoring scheme, a series of damage scenarios are designed to simulate various situations at which the connection joints can experience during their service life. The obtained experimental results, modal parameters and electro-magnetic impedance signatures, are carefully analyzed to recognize the connecting states and the target damage locations. From the analysis, it is shown that the proposed hybrid health monitoring system is successful for acquiring global and local damage information on the structural joints; hence, its effectiveness is verified.