Instrumentation & Measurement Magazine 23-9 - 14

Embedded Split Ring Resonator
Network for Health Monitoring
in Concrete Structures
Erika Pittella, Leopoldo Angrisani, Andrea Cataldo,
Emanuele Piuzzi, and Francesco Fabbrocino

ivil infrastructure systems such as bridges, buildings, dams, pipelines, airports, and heritage
structures are complex engineered systems that play
a fundamental role for the economic and industrial prosperity
of society [1]. In order to build structures that are safe for the
community, standardized design methodologies have been
developed [1]. However, these structures are often subjected
to various external loads and problematic environmental conditions that are difficult to consider during the design phase,
resulting in structural deterioration [2].
Evaluating the health condition of civil infrastructures is of
crucial importance to avoid any failure and for planning maintenance actions [3]. As an example, the closure of a bridge due
to heavy damage can economically affect thousands of people,
and eventually, its failure may cause loss of several lives (e.g.,
Morandi bridge that collapsed in Aug. 2018).
For these reasons, the process of implementing a damage
detection strategy, i.e., Structural Health Monitoring (SHM), is
currently a hot research topic of structural engineering [4]. By
monitoring the actual load and strength of structures, the uncertainty in design calculation, that represents a key factor for
safety, can be reduced. Hence, the residual life of existing structures can be accurately evaluated and at the same time, proper
repair or strengthening, based on the monitored state, can extend the life of the structure [5]. Moreover, monitoring is a
cost-effective solution to preserve civil infrastructures, particularly in developing countries, because monitoring and repair
costs are much lower than the cost of reconstruction [5].
SHM involves the integration of sensors, smart materials,
data transmission, computational power, and processing ability integrated with the structures [6]. In particular, sensors and
technologies should be able to detect a problem without interfering with the structure. A lot of research articles have been
reported on sensors for SHM. Strain gauge sensors for measuring the degree of strain have been widely used in conventional
SHM systems [7]. Not only are strain gauge systems inexpensive and easy to install, but knowledge on interpreting strain
data has also been consolidated. The system proposed in [7]
can diagnose structures and can be easily extended to large

buildings at low cost. MEMS inertial sensors, including accelerometers and gyroscopes, can be used as devices for health
monitoring of structures due to their miniaturized size, low
cost, mass production and three-dimensional detection [8].
A new impedance measurement methodology for an SHM
system based on electromechanical impedance technique is
described in [9]. The system offers precision, speed, low cost,
and versatility and can be integrated into a system based on a
microcontroller DSP and, together with a wireless communication system, allows monitoring of structures whose access is
difficult. A fiber-optic accelerometer system was presented in
[10] and consisted of a sensor head, a control unit for driving
the sensor head and a signal processing unit equipped with a
dedicated algorithm for processing the Moiré fringe signals
into accelerations with a high resolution.
Wireless sensor network (WSN) based structural health
monitoring systems have attracted increasing interest in
recent years [11]. The implementation of a WSN for monitoring structural health parameters is shown in [12], where a
network of different interconnected nodes is presented, providing different measurements (e.g., temperature, humidity,
and deformation). In [13] a measuring system is presented
that consists of wireless sensor modules which act as transmitters and receivers. They are equipped with strain gauges
for long-term monitoring of buildings or engineering facilities
and contain interfaces for additional sensors. The system is applied for transport and traffic structures. A chipless passive
wireless strain and damage detection sensor realized by using a frequency selective surface (FSS) is presented in [14]. The
FSS consists of planar and periodic metal-dielectric arrays
that are based on electromagnetic resonance shift in the presence of a geometric change of the FSS elements. In [15], an SHM
system was proposed that aimed to enable the automatic and
real-time monitoring of a reinforced concrete structure. Attention has been focused on a load cell and an analog temperature
sensor to directly measure the concrete inner stresses and the
temperature where they are installed, respectively.
Recently, Electromagnetic (EM) sensors have received
interest for the monitoring and the prediction of moisture

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December 2020

Instrumentation & Measurement Magazine 23-9

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