Sulfate attack is one of the most frequent environmental attacks affecting concrete structures, which is manifested by
expansive disruption and deterioration of cement paste. However, it is difficult to monitor the deterioration induced by
sulfate attack as these attacks mainly occur in sulfate-bearing soils or ground waters. In this paper, the tentative
experimental investigation on sulfate attack monitoring was carried out by using smart aggregate transducers and an
active sensing method is proposed. A number of plain concrete columns with embedded smart aggregates were
fabricated and then suffered to salt-fog exposure for several months. Active monitoring methods were performed to
detect the deterioration of the specimens using smart aggregates. In addition, testing of the mechanical properties and
water absorption ability of concrete specimens at different deterioration times was performed as well. Then the
transmission mechanism of stress wave in concrete was discussed. The experimental results show that, with the growth
of attacking time, the amplitude of the received signal decreased, and by calculating the damage index, the deterioration
degree of concrete specimens was estimated. It is indicated that the proposed piezoceramic based SA monitoring method
is valid in sulfate attack monitoring.
With the large span, the high redundancy and three-dimensional overall stress in the space structure, there are further
applications in the civil engineering programs. However, due to the more members, the scatter force path and the
complex diversity force transmission modes, which may lead to the complex stress than the ordinary structures in the
space ones. In this paper, firstly, the structural strain responses have been analyzed through the numerical simulation
with snow loading in the national aquatics center (water cube). Then, according to the strains monitoring data and the
relation feature between the temperature loading and structural temperature strains collected from the strain monitoring
system on the effect of the snow loading in the national aquatics center, the temperature loading strains are to be
separated from the snow loading strains with the neural network technique, from which the monitoring data are got in
numerical statement and analyzed, meantime, with which the above numerical simulation results are to be checked and
evaluated. The analysis results shown, in summer, owning to the high alteration amplitude of the temperature difference,
the temperature loading is the control loading to the space structure; on the other hand, in winter, due to the temperature
difference reducing during the process of snowfall, the control loading in the structure is to be transferred from the temperature loading to the snow loading, the effect of the snow loading to the space structure can not to be ignored.
KEYWORDS: Sensors, Data fusion, Structural dynamics, Structural health monitoring, Probability theory, Neural networks, Information fusion, Finite element methods, Civil engineering, Sensor fusion
More and more large span structures have been built or are being built and their health is concerned about by civil
engineers and investors, which arises to the problem of studying on several damage identification methods to give
estimation on the health of the structure and the identification on damage location and damage degree. The damage
identification methods in civil engineering are mostly based on dynamic characteristics, which have difficulties when
applied to practical structures. Meanwhile, the strains of the structural important elements can give more exactly and
more directly information for damage identification on damage location and damage degree. The information fusion for
acceleration sensors and strain sensors is used for making a strategic decision on damage identification and the
Dempster-Shafer evidence theory is used as the information fusion strategic decision, in which the strategic decision
information fusion is a method to give the final decision based on the decision made by each kind of sensors according to
some principle and some synthesized evaluation, that is, the final damage identification results are given based on the
damage identification results using the structural dynamic characteristics and strain measurements. In addition, a finite
element model of large span space shell structure is built and several damage cases of it are simulated, in the example,
the structural dynamic characteristics damage index and strain measurements damage index are used to give the damage
identification results, combining which the final damage identification result by strategic decision fusion is given too,
while the method presented in the paper is proofed to be reliable and effective according to comparing the three kinds of
damage identification results mentioned above.
The design of the control devices for the control system of adjacent structures connected with control devices involves two aspects: the number and placement of the control devices and the control law or the parameters of the control devices. The performance index increment equation is established in this paper by using the conclusions of LQG problem at the condition of the control gain unchanged. Hence the optimum placement method is proved. The step reduced order method is used to overcome the defect of the control gain unchanging and it can be applied to the case in which only a few control devices are to be placed into the building with a large number of story units. The method proposed in this paper gives the optimum design of the number, the placement and the control law of the control devices at the same time.
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