Currently, there have been plenty of researches conducted for two main problems in structural health monitoring, damage and vehicle parameter identification on bridges. However, only a handful of methods could achieve these two functions synchronously, which would cause the redundancy of sensors also the rise of cost in monitoring system. In this paper, a method to identify damage and vehicle parameters, such as axle load, wheelbase and velocity on a bridge simultaneously was proposed, based on the influence line of long-gauge strain. The influence line of long-gauge strain was derived primarily according to conventional strain influence line theory, at the basis of which the relationships among the local element bending stiffness of bridge, vehicle parameters and long-gauge strain were figured out then. The two order difference of long-gauge strain was chosen as the key index to found this identification method. Finally, to verify the reliability of this method, a set of numerical simulations was conducted, whose results showed that this method exhibited good performance.
Recent reports show that modal macro-strain vector (MMSV) obtained by using distributed long-gage FBG sensors is an
effective indicator for damage detection. However, in previous researches, MMSV was always obtained under impulsive
load such as hammer impact. In structural health monitoring of real large-scale structures, however, it is often very
difficult to apply such impulsive load. This paper therefore introduces a new method to abstract MMSV under ambient
excitation. Theoretical deduction reveals that MMSV can be uniquely determined by auto-spectrum of dynamic
macro-strain responses under ambient excitation. Both numerical simulation and experiment were conducted to verify
the proposed methods. Simulation results showed that that the identified frequencies and MMSV vectors under random
excitation are in good agreement with those obtained from theoretical analysis, while experimental results showed the
identified frequencies and MMSV agreed well with those obtained using point impulsive excitation.
In this paper, the self-sensing and mechanical properties of concrete structures strengthened with a novel type of smart
basalt fiber reinforced polymer (BFRP) bars were experimentally studied, wherein the sensing element is Brillouin
scattering-based distributed optical fiber sensing technique. First, one of the smart bars was applied to strengthen a 2m
concrete beam under a 4-points static loading manner in the laboratory. During the experiment, the bar can measure the
inner strain changes and monitor the randomly distributed cracks well. With the distributed strain information along the
bar, the distributed deformation of the beam can be calculated, and the structural health can be monitored and evaluated
as well. Then, two smart bars with a length of about 70m were embedded into a concrete airfield pavement reinforced by
long BFRP bars. In the field test, all the optical fiber sensors in the smart bars survived the whole concrete casting
process and worked well. From the measured data, the concrete cracks along the pavement length can be easily
monitored. The experimental results also confirmed that the bars can strengthen the structures especially after the
yielding of steel bars. All the results confirm that this new type of smart BFRP bars show not only good sensing
performance but also mechanical performance in the concrete structures.
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.
Space-time spreading (STS) and orthogonal transmit diversity (OTD) are two transmit diversity schemes proposed by CDMA2000 standard. In this paper, performance comparison analysis of the two transmit diversity schemes in multi-path channel are carried out. Link level simulation in forward link CDMA2000 is performed in IMT-2000 channel. Performance analysis and simulation results show that STS outperforms OTD under the same transmitting power.
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