Singh, 2020
the orientation of the gage, because the gauge measures
with steeper strain gradients at higher loading stages. Their
approach to stress transfer can provide very
comprehensive results of reinforcement and concrete
strains, the bond stress and slip values over the entire
distribution of the element, provided the implemented
bond-slip model was accurate.
orthogonal extensional strains and associated shear strains.
They use DMI technology permits periodic inspection of a
DMI gage centered on a fastener hole containing a fastener
on in-service equipment to determine the presence of
cracks at scheduled inspection intervals or after an unusual
loading. This comment is based on the discussion by
Timoshenko and Goodier cited above. This does not mean
that electrical resistance gages do not have a role. They
also suggest that electrical resistance gages may be more
economically and technologically informative, if deployed
differently than currently deployed on surfaces with
fastener hole.
SEC (Soft Elastomer Capacitors) and basic
function on crack estimation
A study that was focused on examining the suitability
of a novel large-area strain-based sensing technology for
presented a study that was focused on examining the
suitability of a novel large area strain-based sensing
technology for monitoring fatigue cracking in steel
bridges. They take SEC which is a large-size, flexible,
low-cost, and mechanically-robust capacitive strain gage,
and has a wide strain measuring range, making it a
promising tool for monitoring cracks in bridges. Their
studies have verified the SEC’s capabilities for monitoring
low-cycle fatigue cracking, but high cycle fatigue cracking
is characterized by a small crack openings, which presents
was a new challenge for a capacitance-based sensor such
as the SEC. To achieve that monitoring solution for
fatigue cracking in steel bridges, they use the pk-pk
amplitude of the sensor’s measurement to construct an
indicator of crack growth. Then they establish a crack
monitoring algorithm to compute CGIs as a normalized
pk-pk amplitude in the frequency domain. The sensor’s
capabilities and the proposed algorithm was evaluated
through experimental testing under various stress ratios, R.
They got some conclusions that the developed algorithm
was able to overcome noise infiltration, and resulted in an
excellent correlation between increasing fatigue crack
length and increasing CGI. Therefore, the proposed crack
monitoring algorithm was validated by the test data. They
state that the proposed crack monitoring algorithm was
able to robustly monitor the growth of high cycle fatigue
cracks under various loading conditions and provide
consistent results for the three stress ratios that were
studied. With the introduction of the monitoring algorithm,
the SEC was found to be capable of serving as a
monitoring device for propagating fatigue cracks in steel
bridges.
FBG optical strain gauge
To increase the precision for crack determining,
reinforcement bars attained from the FBG optical strain
gauge and ordinary tensor strain gauge in a comparison. In
addition, they carried out numerical calculations using the
stress transfer approach to obtain the numerical strain
variation along the reinforced concrete prism reinforcing
bar. In their experimental techniques, they provide strain
variations along the steel bar with reasonable accuracy and
smoothness, however, the specimen strain results of the
fiber Bragg grating optical gauge test displayed anomalies,
particularly near the end of the specimen. Then the
measured strains which they use were larger than the strain
value estimated for a bare bar assuming the experimental
value of the modulus of elasticity of the bar. In addition,
the FBG recordings were lacking consistency regarding
the symmetry condition of the left and the right side of the
member. Due to fluctuations in the strain values recorded
by FBG sensors and the rather rare spacing between the
sensors, it cannot be firmly asserted whether the
phenomenon was related to the debonding effect proposed
in previous research by the authors. Their effect implies
altered bond behavior between the reinforcement and the
concrete material surrounding it around the location of the
cracks or elements’ ends. A comparison of the numerical
results with appropriate experimental strain curves of the
steel reinforcement showed that the Model Code 2010
bond-slip equation could provide sufficiently accurate
results when coupled with the stress transfer approach for
the Ø20 mm specimens. However, their additional tests
with different diameter bars and reinforcement ratios
would help them either affirm or negate the findings.
Some discrepancies in numerical and experimental strain
comparison appeared at the highest loading of the FBG
specimen. The overall observed behavior was parabolic,
Detection, localization, and quantification of
cracks by SEC(soft elastomeric capacitors)
the detection, localization, and quantification of cracks in
concrete. The sensing skin, constituted from an array of
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