In this paper, based on the distributed optical fiber strain sensing technology of pulse-pre-pump Brillouin Optical Time
Domain Analysis (PPP-BOTDA), the creep properties of two types of optical fiber sensors, i.e. single mode optical fiber
with jacket (Type-A) and optical fiber with UV resin coating (Type-B), were studied at different load (60g~600g)
amplitudes. Experimental results show that there exists some creep for both types in initial loading period and tend to
level off with time. But for Type-B, the strain variation is 5% of initial strain, and the stabilization time is about 48h,
both of which are obviously smaller than those of Type-A. As a result, it is revealed that Type-B is characterized by a
smaller creep, suitable for the long-term monitoring of infrastructures.
In general, macro-strain is an effective index for health monitoring of civil infrastructures, which can reveal the
unforeseen damage accumulation. However, it is difficult to acquire precise strain distribution with existing
fully-distributed optical fiber sensing techniques. Based on the distributed optical fiber strain sensing technique of
pulse-prepump Brillouin Optical Time Domain Analysis (PPP-BOTDA), a new optical fiber sensor with improved strain
sensitivity (OFSISS) is proposed to enhance the precision of macro-strain measurements. The most advantage of the
OFSISS sensor is that it can markedly reduce the measurement error of strain data with a proper designed magnified
coefficient. The OFSISS has also good designability and durability according to detailed sensing requirements. Results
of uniaxial tensile experiment show not only the high accuracy and precision of the OFSISS but also an important fact
that the measured magnified coefficients of the manufactured OFSISSs with a recoating process agree well with the
designed values. The bending experiment of using a steel beam illustrates that the linearity and reliability of macro-strain
measurement from the OFSISS are good enough for the application in actual macro-strain monitoring and structural
deformation monitoring.
In this paper, a new type of self-sensing basalt fiber reinforced polymer (BFRP) bars is developed with using the
Brillouin scattering-based distributed optic fiber sensing technique. During the fabrication, optic fiber without buffer and
sheath as a core is firstly reinforced through braiding around mechanically dry continuous basalt fiber sheath in order to
survive the pulling-shoving process of manufacturing the BFRP bars. The optic fiber with dry basalt fiber sheath as a
core embedded further in the BFRP bars will be impregnated well with epoxy resin during the pulling-shoving process.
The bond between the optic fiber and the basalt fiber sheath as well as between the basalt fiber sheath and the FRP bar
can be controlled and ensured. Therefore, the measuring error due to the slippage between the optic fiber core and the
coating can be improved. Moreover, epoxy resin of the segments, where the connection of optic fibers will be performed,
is uncured by isolating heat from these parts of the bar during the manufacture. Consequently, the optic fiber in these
segments of the bar can be easily taken out, and the connection between optic fibers can be smoothly carried out. Finally,
a series of experiments are performed to study the sensing and mechanical properties of the propose BFRP bars. The
experimental results show that the self-sensing BFRP bar is characterized by not only excellent accuracy, repeatability
and linearity for strain measuring but also good mechanical property.
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