This paper proposes a new way for guided wave structural health monitoring using in-plane shear (d36 type)
piezoelectric wafer active sensors phased arrays. Conventional piezoelectric wafer active sensors phased arrays based on
inducing into specific Lamb wave modes (d31 type) has already widely used for health monitoring of the thin-wall
structures. Rather than Lamb wave modes, the in-plane shear piezoelectric wafer active sensors phased arrays induces in-plane
shear horizontal (SH) guided waves. The SH guided waves are distinct with the Lamb waves with simple
waveform and less additional converted wave modes and the zero symmetric mode (SH0) is non-dispersive. In this paper,
the advantage of the shear horizontal wave and the in-plane shear piezoelectric wafers capability to generate SH waves is
first reviewed. Then finite element analysis of a 4-in-plane shear wafer active sensors phased array embedded on a
rectangular aluminium plate is performed. In addition, numerical simulations with respect to creaks with different sizes
as well as locations are implemented by the in-plane shear wafer active sensors phased array. For comparison purposes,
the same numerical simulations using the conventional piezoelectric wafer active sensors phased arrays are also
employed at the same time. Results indicate that the in-plane shear (d36 type) piezoelectric wafer active sensors phased
arrays has the potential to identify damage location and assess damage severity in structural health monitoring.
This paper proposes a novel and effective method to identify the damage in the 2-D beam via Lamb wave. Two problems in the structural damage identification: damage location and damage severity are solved based on the theory of compressive sampling (CS) which indicates that sparse or compressible signals can be reconstructed using just a few measurements. Because of the sparsity nature of the damage, a database of damage features is established via a sparse representation for damage identification and assessing. Specifically, this proposed method consists of two steps: damage database establishing and feature matching. In the first step, the features database of both the healthy structure and the damaged structure are represented by the Lamb wave which propagates in the 2-D beam. Then in the matching step, expressing the test modal feature as a linear combination of the bases of the over-complete reference feature database which is constructed by concatenating all modal features of all candidate damage locations builds a highly underdetermined linear system of equations with an underlying sparse representation, which can be correctly recovered by ℓ1-minimization based on CS theory; the non-zero entry in the recovered sparse representation directly identifies the damage location and severity. In addition, numerical simulation is conducted to verify the method. This method of identifying damage location and assessing damage severity, using limited Lamb wave features, obtains good result.
This work presents guided wave generation, sensing, and damage detection in metallic plates using in-plane shear (d36 type) piezoelectric wafers as actuators and sensors. The conventional Lead zirconate titanate (PZT) based on induced in-plane normal strain (d31 type) has been widely used to excite and receive guided wave in plates, pipes or thin-walled structures. The d36 type of piezoelectric wafers however induces in-plane (or called face) shear deformation in the plane normal to its polarization direction. This form of electromechanical coupling generates more significant shear horizontal waves in certain wave propagation directions, whose amplitudes are much greater than those of Lamb waves. In this paper, an analysis of shear horizontal (SH) waves generated using in-plane shear electromechanical coupling is firstly presented, followed by a multiphysics finite element analysis for comparison purpose. Voltage responses of both conventional d31 and new d36 sensors are obtained for comparison purpose. Results indicate this type of wafers has potential for simply providing quantitative estimation of damage in structural health monitoring.
Acoustic emission (AE) technique is an effective method in the nondestructive testing (NDT) field of civil engineering.
During the last two decades, Fiber reinforced polymer (FRP) has been widely used in repairing and strengthening
concrete structures. The damage state of FRP strengthened concrete structures has become an important issue during the
service period of the structure and it is a meaningful work to use AE technique as a nondestructive method to assess its
damage state. The present study reports AE monitoring results of axial compression tests carried on basalt fiber
reinforced polymer (BFRP) confined concrete columns and three-point-bending tests carried on BFRP reinforced
concrete beams. AE parameters analysis was firstly utilized to give preliminary results of the concrete fracture process of
these specimens. It was found that cumulative AE events can reflect the fracture development trend of both BFRP
confined concrete columns and BFRP strengthened concrete beams and AE events had an abrupt increase at the point of
BFRP breakage. Then the fracture process of BFRP confined concrete columns and BFRP strengthened concrete beams
was studied through RA value-average frequency analysis. The RA value-average frequency tendencies of BFRP
confined concrete were found different from that of BFRP strengthened concrete beams. The variation tendency of
concrete crack patterns during the loading process was revealed.
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.
The stay cables are generally regarded as the most critical component of the cable-stayed bridges. Normal vehicle loads
will cause fatigue damage of the cables made of parallel steel wire. In addition, the stay cables also suffer from the
challenges of corrosion, fatigue and their coupled effects. Therefore it is important to detect the damage of wires with the
cables before the cables fails catastrophically. Structural health monitoring (SHM) is now regarded as an essential tool
to evaluate the status of the structure. In this paper, a corroded parallel steel wire, which are removed from a real bridge,
was carried out under the fatigue loading to simulate the damage procedure, i.e. the producing and propagation of
damage or crack. Piezoelectric transformers bonded to the cable are used to monitor and evaluate the damage
propagation during the test. Moreover, the fatigue properties of corroded parallel wire cable are investigated in this
The complex external environment for civil engineering structures results in the structural vibration properties varying
with external conditions, such as humidity and temperature. For the vibration-based structural health monitoring
techniques, for example damage identification, modal updating etc., above characteristics will result in the vibration-based
techniques invalid. Other researchers have reported that modal frequencies varied significantly due to temperature
change, but the humidity affect structural vibration properties in another manner. This paper discusses the variation of
frequencies and mode shapes with respect to humidity and temperature changes for concrete structures, for which the
changing of moisture will affect the density of materials, and the changing of temperature will affect the stiffness of
structures. This paper models these two factors with finite element model approach based on the theoretical analysis, and
numerical results obtained on the FE model of a concrete bridge deck are reported.
Filament wound pressure vessels have been extensively used in industry and engineering. The existing damage detection
and health monitoring methods for these vessels, such as X-ray and ultrasonic scan, can not meet the requirement of
online damage detection; moreover optical grating fibre can only sense the local damage, but not the damage far away
from the location of sensors. Vibration-based damage detection methods have the potential to meet such requirements.
There methods are based on the fact that damages in a structure results in a change in structural dynamic characteristics.
A damage detection method based on a residual associated with output-only subspace-based modal identification and
global or focused chi^2-tests built on that residual has been proposed and successfully experimented on a variety of test
cases. The purpose of this work is to describe the damage detection method and apply this method to assess the
composite structure filled with fluid. The results of identification and damage detection will be presented.
A benchmark study is a valid way to make comparison of kinds of Structural Health Monitoring technologies, for example modal identification, finite element model updating, damage identification and so on. Several successful benchmark SHM problems were developed by IASC-ASCE SHM Task Group and the encouraging analytical studies results were obtained. But this benchmark study is based on a steel-frame scale-model structure built in the laboratory. Due to the striking difference in structure’s properties, SHM system and so on between the structure in the laboratory and the real structure, many SHM technologies developed in the laboratory is not applicable to the real structure. Thus a new benchmark study based on a real structure is developed in this paper. The first and the second phase of a benchmark problem based on SHM system for Binzhou Yellow River Highway Bridge have been detailed and the criterion of benchmark problem are given simultaneously.