Special Issue "Structural Health Monitoring (SHM) of Civil Structures"

A special issue of Applied Sciences (ISSN 2076-3417).

Deadline for manuscript submissions: closed (31 March 2017)

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Guest Editor
Prof. Dr. Gangbing Song

John and Rebecca Moores Professor, Professor of Mechanical Engineering, University of Houston, Houston, TX, USA
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Interests: smart materials and structures; structural vibration control; piezoceramics; ultrasonic transducers; structural health monitoring and damage detection
Co-Guest Editor
Prof. Chuji Wang

Department of Physics and Astronomy, Mississippi State University, P.O. Drawer 5167, Mississippi State, MS 39762, USA
Website | E-Mail
Interests: fiber optic sensors, fiber ring down sensors, laser spectroscopy, laser diagnostics measurements and monitoring, structural health monitoring
Co-Guest Editor
Dr. Bo Wang

School of Civil Engineering, Southwest Jiaotong University,Chengdu, Sichuan,China
Website | E-Mail
Interests: rock burst monitoring, rock bolt and monitoring, underground blast monitoring, tunnel safety, tunnel structural health monitoring, underground space monitoring

Special Issue Information

Dear Colleagues,

Recent progress in sensing technology and techniques have allowed us to gain insight into the diagnosis of diseases as well as determine the remaining service life of a device. The influence of such progress has also found its place in the diagnosis of structural conditions. In the field of structural health monitoring, researchers have made great strides in applying new sensing technology towards determining the integrity of a wide variety of structures and warning occupants of impending danger due to imminent structural failure. This Special Issue will showcase some of the latest efforts advancing the frontiers of structural health monitoring. Topics include, but are not limited to: sensors for structural health monitoring; damage detection and characterization/feature extraction algorithms; data transmission for embedded systems; structural warning systems; validation of structural health monitoring techniques; case studies of health monitoring of infrastructures (bridges, tunnels, pipelines, …); model-based structural service life prediction methods; etc.

Prof. Dr. Gangbing Song
Guest Editor

Manuscript Submission Information

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Keywords

  • Structural health monitoring
  • Sensor development
  • Bridges
  • Tunnels
  • Pipelines
  • Early warning
  • Embedded sensors
  • Damage detection and characterization
  • Damage feature extraction algorithms

Published Papers (32 papers)

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Editorial

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Open AccessEditorial
Structural Health Monitoring (SHM) of Civil Structures
Appl. Sci. 2017, 7(8), 789; https://doi.org/10.3390/app7080789
Received: 31 July 2017 / Revised: 31 July 2017 / Accepted: 31 July 2017 / Published: 4 August 2017
Cited by 23 | PDF Full-text (143 KB) | HTML Full-text | XML Full-text
Abstract
As newer and more reliable ways of construction were developed, civilization began to spread out further and retain functional infrastructure for longer periods of time.[...] Full article

Research

Jump to: Editorial, Review

Open AccessArticle
A Wireless Sensor Network Using GNSS Receivers for a Short-Term Assessment of the Modal Properties of the Neckartal Bridge
Appl. Sci. 2017, 7(6), 626; https://doi.org/10.3390/app7060626
Received: 31 March 2017 / Revised: 30 May 2017 / Accepted: 8 June 2017 / Published: 16 June 2017
Cited by 8 | PDF Full-text (5265 KB) | HTML Full-text | XML Full-text
Abstract
In this article, we present a novel structural health monitoring system based on a wireless sensor network for GNSS (global navigation satellite system) receivers. The GNSS network presented here consists of three GNSS rover stations and one base station that are deployed at [...] Read more.
In this article, we present a novel structural health monitoring system based on a wireless sensor network for GNSS (global navigation satellite system) receivers. The GNSS network presented here consists of three GNSS rover stations and one base station that are deployed at the Neckartal bridge on the Autobahn A81 in southwest Germany. The newly-developed GNSS sensor nodes support satellite data logging up to a sampling rate of 20 Hz. Due to the ultra-low-power consumption achieved by the wake-up receiver during inactive periods, the nodes offer a lifetime from 20 to almost 200 days, without energy harvesting and depending on the satellite data logging period. By performing differential post-processing, precise positioning information in the millimeter range could be achieved. Using the GNSS sensors, we determined resonant frequencies at 0.33 Hz and 1.31 Hz, mainly in the lateral direction of the bridge. To verify the GNSS results, we placed an accelerometer on the bridge. The frequencies detected by the acceleration sensor correspond well to the frequencies found by the GNSS sensors, although the accelerometer measured further higher frequencies as it is probably more sensitive to small amplitudes. Full article
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Open AccessArticle
Fire Damage Assessment of Reinforced Concrete Structures Using Fuzzy Theory
Appl. Sci. 2017, 7(5), 518; https://doi.org/10.3390/app7050518
Received: 30 March 2017 / Revised: 4 May 2017 / Accepted: 9 May 2017 / Published: 16 May 2017
Cited by 3 | PDF Full-text (5271 KB) | HTML Full-text | XML Full-text
Abstract
Once a reinforced concrete (RC) structure is damaged by fire, the fire damage assessment should proceed to take appropriate post-fire actions, including the decision-making of whether it can be repaired for reuse or not. Since the assessment results of current fire damage diagnosis [...] Read more.
Once a reinforced concrete (RC) structure is damaged by fire, the fire damage assessment should proceed to take appropriate post-fire actions, including the decision-making of whether it can be repaired for reuse or not. Since the assessment results of current fire damage diagnosis methods, however, highly depend on the subjective judgment of inspectors, it is hard to ensure their objectiveness and reliability. This study, therefore, aims to develop a new fire damage diagnosis system (FDDS) based on fuzzy theory that can provide objective and comprehensive evaluation results by considering all of the damage conditions observed from the inspection on RC structural members exposed to fire. In addition, the FDDS was applied to an actual fire-damaged case reported by the Architectural Institute of Japan (AIJ, 2009), and it appears that the proposed method provides a reasonable estimation on the fire damage grade of the fire-damaged RC members. Full article
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Open AccessArticle
An Investigation on Eddy Current Pulsed Thermography to Detect Surface Cracks on the Tungsten Carbide Matrix of Polycrystalline Diamond Compact Bit
Appl. Sci. 2017, 7(4), 429; https://doi.org/10.3390/app7040429
Received: 22 January 2017 / Revised: 11 April 2017 / Accepted: 17 April 2017 / Published: 23 April 2017
Cited by 4 | PDF Full-text (4037 KB) | HTML Full-text | XML Full-text
Abstract
Polycrystalline diamond compact (PDC) bits are commonly used drill bits in the petroleum drilling industry. Cracks often occur on the surface of a bit, which may result in the unexpected suspension of the drilling operation, or even accidents. Therefore, the detection of surface [...] Read more.
Polycrystalline diamond compact (PDC) bits are commonly used drill bits in the petroleum drilling industry. Cracks often occur on the surface of a bit, which may result in the unexpected suspension of the drilling operation, or even accidents. Therefore, the detection of surface cracks on PDC bits is of great importance to ensure continuous drilling operation and to prevent accidents. However, it is extremely difficult to detect such cracks by visual inspection or other traditional nondestructive testing (NDT) techniques due to the small size of cracks and the irregular geometry of bits. As one emerging NDT technique, eddy current pulsed thermography (ECPT) can instantly detect surface cracks on metal parts with irregular geometry. In this study, the feasibility of ECPT of detecting surface cracks on the tungsten carbide matrix of PDC bits was investigated. A successive scanning detection mode is proposed to detect surface cracks by using ECPT with a low power heating excitation unit and small-size coils. The influence of excitation duration on the detection result was also investigated. In addition, principal component analysis (PCA) was employed to process the acquired IR image sequences to improve detection sensitivity. Finally, the whole shape of a crack was restored with processed images containing varied cracks segments. Based on the experimental results, we conclude that the surface cracks on the tungsten carbide matrix of PDC bit can be detected effectively and conveniently by ECPT in scanning mode with the aid of PCA. Full article
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Open AccessArticle
Nuclear Power Plant Prestressed Concrete Containment Vessel Structure Monitoring during Integrated Leakage Rate Testing Using Fiber Bragg Grating Sensors
Appl. Sci. 2017, 7(4), 419; https://doi.org/10.3390/app7040419
Received: 21 February 2017 / Revised: 6 April 2017 / Accepted: 16 April 2017 / Published: 20 April 2017
Cited by 4 | PDF Full-text (7219 KB) | HTML Full-text | XML Full-text
Abstract
As the last barrier of nuclear reactor, prestressed concrete containment vessels (PCCVs) play an important role in nuclear power plants (NPPs). To test the mechanical property of PCCV during the integrated leakage rate testing (ILRT), a fiber Bragg grating (FBG) sensor was used [...] Read more.
As the last barrier of nuclear reactor, prestressed concrete containment vessels (PCCVs) play an important role in nuclear power plants (NPPs). To test the mechanical property of PCCV during the integrated leakage rate testing (ILRT), a fiber Bragg grating (FBG) sensor was used to monitor concrete strain. In addition, a finite element method (FEM) model was built to simulate the progress of the ILRT. The results showed that the strain monitored by FBG had the same trend compared to the inner pressure variation. The calculation results showed a similar trend compared with the monitoring results and provided much information about the locations in which the strain sensors should be installed. Therefore, it is confirmed that FBG sensors and FEM simulation are very useful in PCCV structure monitoring. Full article
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Open AccessArticle
Improved Tensor-Based Singular Spectrum Analysis Based on Single Channel Blind Source Separation Algorithm and Its Application to Fault Diagnosis
Appl. Sci. 2017, 7(4), 418; https://doi.org/10.3390/app7040418
Received: 9 March 2017 / Revised: 8 April 2017 / Accepted: 16 April 2017 / Published: 20 April 2017
Cited by 2 | PDF Full-text (6866 KB) | HTML Full-text | XML Full-text
Abstract
To solve the problem of multi-fault blind source separation (BSS) in the case that the observed signals are under-determined, a novel approach for single channel blind source separation (SCBSS) based on the improved tensor-based singular spectrum analysis (TSSA) is proposed. As the most [...] Read more.
To solve the problem of multi-fault blind source separation (BSS) in the case that the observed signals are under-determined, a novel approach for single channel blind source separation (SCBSS) based on the improved tensor-based singular spectrum analysis (TSSA) is proposed. As the most natural representation of high-dimensional data, tensor can preserve the intrinsic structure of the data to the maximum extent. Thus, TSSA method can be employed to extract the multi-fault features from the measured single-channel vibration signal. However, SCBSS based on TSSA still has some limitations, mainly including unsatisfactory convergence of TSSA in many cases and the number of source signals is hard to accurately estimate. Therefore, the improved TSSA algorithm based on canonical decomposition and parallel factors (CANDECOMP/PARAFAC) weighted optimization, namely CP-WOPT, is proposed in this paper. CP-WOPT algorithm is applied to process the factor matrix using a first-order optimization approach instead of the original least square method in TSSA, so as to improve the convergence of this algorithm. In order to accurately estimate the number of the source signals in BSS, EMD-SVD-BIC (empirical mode decomposition—singular value decomposition—Bayesian information criterion) method, instead of the SVD in the conventional TSSA, is introduced. To validate the proposed method, we applied it to the analysis of the numerical simulation signal and the multi-fault rolling bearing signals. Full article
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Open AccessArticle
Research on the Blind Source Separation Method Based on Regenerated Phase-Shifted Sinusoid-Assisted EMD and Its Application in Diagnosing Rolling-Bearing Faults
Appl. Sci. 2017, 7(4), 414; https://doi.org/10.3390/app7040414
Received: 7 January 2017 / Revised: 1 April 2017 / Accepted: 17 April 2017 / Published: 19 April 2017
Cited by 11 | PDF Full-text (5574 KB) | HTML Full-text | XML Full-text
Abstract
To improve the performance of single-channel, multi-fault blind source separation (BSS), a novel method based on regenerated phase-shifted sinusoid-assisted empirical mode decomposition (RPSEMD) is proposed in this paper. The RPSEMD method is used to decompose the original single-channel vibration signal into several intrinsic [...] Read more.
To improve the performance of single-channel, multi-fault blind source separation (BSS), a novel method based on regenerated phase-shifted sinusoid-assisted empirical mode decomposition (RPSEMD) is proposed in this paper. The RPSEMD method is used to decompose the original single-channel vibration signal into several intrinsic mode functions (IMFs), with the obtained IMFs and original signal together forming a new observed signal for the dimensional lifting. Therefore, an undetermined problem is transformed into a positive definite problem. Compared with the existing EMD method and its improved version, the proposed RPSEMD method performs better in solving the mode mixing problem (MMP) by employing sinusoid-assisted technology. Meanwhile, it can also reduce the computational load and reconstruction errors. The number of source signals is estimated by adopting singular value decomposition (SVD) and Bayes information criterion (BIC). Simulation analysis has demonstrated the superiority of this method being applied in multi-fault BSS. Furthermore, its effectiveness in identifying the multi-fault features of rolling-bearing has been also verified based on a test rig. Full article
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Open AccessFeature PaperArticle
Hierarchical Wavelet-Aided Neural Intelligent Identification of Structural Damage in Noisy Conditions
Appl. Sci. 2017, 7(4), 391; https://doi.org/10.3390/app7040391
Received: 20 January 2017 / Revised: 4 April 2017 / Accepted: 5 April 2017 / Published: 14 April 2017
Cited by 8 | PDF Full-text (2593 KB) | HTML Full-text | XML Full-text
Abstract
A sophisticated hierarchical neural network model for intelligent assessment of structural damage is constructed by the synergetic action of auto-associative neural networks (AANNs) and Levenberg-Marquardt neural networks (LMNNs). With the model, AANNs aided by the wavelet packet transform are firstly employed to extract [...] Read more.
A sophisticated hierarchical neural network model for intelligent assessment of structural damage is constructed by the synergetic action of auto-associative neural networks (AANNs) and Levenberg-Marquardt neural networks (LMNNs). With the model, AANNs aided by the wavelet packet transform are firstly employed to extract damage features from measured dynamic responses and LMNNs are then utilized to undertake damage pattern recognition. The synergetic functions endow the model with a unique mechanism of intelligent damage identification in structures. The model is applied for the identification of damage in a three-span continuous bridge, with particular emphasis on noise interference. The results show that the AANNs can produce a low-dimensional space of damage features, from which LMNNs can recognize both the location and the severity of structural damage with great accuracy and strong robustness against noise. The proposed model holds promise for developing viable intelligent damage identification technology for actual engineering structures. Full article
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Open AccessArticle
Experimental Damage Identification of a Model Reticulated Shell
Appl. Sci. 2017, 7(4), 362; https://doi.org/10.3390/app7040362
Received: 17 February 2017 / Revised: 29 March 2017 / Accepted: 29 March 2017 / Published: 6 April 2017
Cited by 15 | PDF Full-text (2488 KB) | HTML Full-text | XML Full-text
Abstract
The damage identification of a reticulated shell is a challenging task, facing various difficulties, such as the large number of degrees of freedom (DOFs), the phenomenon of modal localization and transition, and low modeling accuracy. Based on structural vibration responses, the damage identification [...] Read more.
The damage identification of a reticulated shell is a challenging task, facing various difficulties, such as the large number of degrees of freedom (DOFs), the phenomenon of modal localization and transition, and low modeling accuracy. Based on structural vibration responses, the damage identification of a reticulated shell was studied. At first, the auto-regressive (AR) time series model was established based on the acceleration responses of the reticulated shell. According to the changes in the coefficients of the AR model between the damaged conditions and the undamaged condition, the damage of the reticulated shell can be detected. In addition, the damage sensitive factors were determined based on the coefficients of the AR model. With the damage sensitive factors as the inputs and the damage positions as the outputs, back-propagation neural networks (BPNNs) were then established and were trained using the Levenberg–Marquardt algorithm (L–M algorithm). The locations of the damages can be predicted by the back-propagation neural networks. At last, according to the experimental scheme of single-point excitation and multi-point responses, the impact experiments on a K6 shell model with a scale of 1/10 were conducted. The experimental results verified the efficiency of the proposed damage identification method based on the AR time series model and back-propagation neural networks. The proposed damage identification method can ensure the safety of the practical engineering to some extent. Full article
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Open AccessArticle
The Experimental Study of the Temperature Effect on the Interfacial Properties of Fully Grouted Rock Bolt
Appl. Sci. 2017, 7(4), 327; https://doi.org/10.3390/app7040327
Received: 9 January 2017 / Revised: 11 March 2017 / Accepted: 24 March 2017 / Published: 27 March 2017
Cited by 5 | PDF Full-text (2980 KB) | HTML Full-text | XML Full-text
Abstract
This study analyzes the phenomenon of performance deterioration in fully grouted rock bolts in tunnels with a dry, hot environment and high geothermal activity with a focus on temperature effects on interfacial bond performance. Three groups of fully grouted rock bolt specimens were [...] Read more.
This study analyzes the phenomenon of performance deterioration in fully grouted rock bolts in tunnels with a dry, hot environment and high geothermal activity with a focus on temperature effects on interfacial bond performance. Three groups of fully grouted rock bolt specimens were designed based on similar mechanical principles. They were produced and maintained at 20 °C, 35 °C, and 50 °C. Through the indoor gradual loading tensile test of specimens, variations of axial force and shear stress between the rock bolt and mortar adhesive interface were obtained under different environmental temperatures. Distribution of the axial force and shear stress on the anchorage section were found under different tensile forces. Results showed that, with an increase in specimen environmental temperature, maximum shear stress of the rock bolt section became smaller, while shear stress distribution along the rock bolt segment became more uniform. In addition, the axial force value at the same position along the pull end was greater, while axial stress along the anchorage’s length decayed faster. With an increase in tensile force under different temperatures, the axial force and maximum shear stress of rock bolt specimens along the anchorage section has a corresponding increase. Full article
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Open AccessArticle
Seismic Damage Evaluation of Concrete-Encased Steel Frame-Reinforced Concrete Core Tube Buildings Based on Dynamic Characteristics
Appl. Sci. 2017, 7(4), 314; https://doi.org/10.3390/app7040314
Received: 8 December 2016 / Revised: 5 February 2017 / Accepted: 16 March 2017 / Published: 23 March 2017
Cited by 10 | PDF Full-text (8322 KB) | HTML Full-text | XML Full-text
Abstract
To evaluate damage state and residual resistance of concrete-encased steel frame-reinforced concrete core tube buildings under earthquake actions, a criterion of damage assessment based on dynamic characteristics is proposed in this paper. Dynamic characterization experiments were conducted on a 10-story and 1/5 scaled [...] Read more.
To evaluate damage state and residual resistance of concrete-encased steel frame-reinforced concrete core tube buildings under earthquake actions, a criterion of damage assessment based on dynamic characteristics is proposed in this paper. Dynamic characterization experiments were conducted on a 10-story and 1/5 scaled building model using velocity sensors on each floor, and natural frequencies were obtained based on the measured data. Modal analysis was carried out using a nonlinear finite element program, and the simulation results of the dynamic characteristics agreed well with experimental ones. Then, the damage processes under different seismic wave inputs were revealed based on finite element analysis, and the max story drift angle was chosen to reflect the damage state and to quantify the degree of damage. A criterion of seismic damage assessment is proposed based on the relationship between the quantitative damage value and the dynamic characteristics, in which the higher order modes were considered. Moreover, influencing factors, including earthquake intensity and structural stiffness ratio, were analyzed, and the results indicated that the proposed damage index based on dynamic characteristics can account for the higher-order modes and provides an innovative approach to evaluate the seismic damage. Full article
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Open AccessArticle
Researching a Fuzzy- and Performance-Based Optimization Method for the Life-Cycle Cost of SRHPC Frame Structures
Appl. Sci. 2017, 7(3), 269; https://doi.org/10.3390/app7030269
Received: 29 December 2016 / Revised: 29 January 2017 / Accepted: 7 February 2017 / Published: 8 March 2017
Cited by 2 | PDF Full-text (1911 KB) | HTML Full-text | XML Full-text
Abstract
In order to solve two problems with the traditional optimization method of steel reinforced high strength high performance concrete (SRHPC) frame structures, a fuzzy mathematics and performance-based optimization method for the life-cycle cost of SRHPC frame structures is proposed. In the optimization program, [...] Read more.
In order to solve two problems with the traditional optimization method of steel reinforced high strength high performance concrete (SRHPC) frame structures, a fuzzy mathematics and performance-based optimization method for the life-cycle cost of SRHPC frame structures is proposed. In the optimization program, quantitative seismic performance indicators of SRHPC frame structures are determined according to the experimental results of SRHPC columns. Furthermore, by considering the fuzzy reliability of structures under each performance level, the life-cycle optimization model of SRHPC frame structures can be established. In order to solve the problem of too many variables and constraints in the optimization process, a two-step optimization method is proposed. Finally, an optimization example is carried out through the MATLAB program to demonstrate the feasibility of this model. Full article
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Open AccessArticle
Reconstruction to Sensor Measurements Based on a Correlation Model of Monitoring Data
Appl. Sci. 2017, 7(3), 243; https://doi.org/10.3390/app7030243
Received: 19 January 2017 / Revised: 25 February 2017 / Accepted: 28 February 2017 / Published: 3 March 2017
Cited by 4 | PDF Full-text (4886 KB) | HTML Full-text | XML Full-text
Abstract
A sensor failure will lead to sensor measurement distortion, and may reduce the reliability of the whole structure analysis. This paper studies the method of monitoring information reconstruction based on the correlation degree. For the faulty sensor, the correlation degree of the normal [...] Read more.
A sensor failure will lead to sensor measurement distortion, and may reduce the reliability of the whole structure analysis. This paper studies the method of monitoring information reconstruction based on the correlation degree. For the faulty sensor, the correlation degree of the normal response of this sensor and the measurements of the other sensors is calculated, which is also called the correlation degree of reconstructed variables and response variables. By comparing the correlation degrees, the response variables, which are needed to establish the correlation model, are determined. The correlation model between the reconstructed variables and the response variables is established by the partial least square method. The value of the correlation degrees between the reconstructed variables and the response variables, the amount of the monitoring data which is used to determine the coefficients of the correlation model, and the number of the response variables are used to discuss the influence factors of the reconstruction error. The stress measurements of structural health monitoring system of Shenzhen Bay Stadium is taken as an example, and the effectiveness of the method is verified and the practicability of the method is illustrated. Full article
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Open AccessArticle
Numerical Analysis and Optimization on Piezoelectric Properties of 0–3 Type Piezoelectric Cement-Based Materials with Interdigitated Electrodes
Appl. Sci. 2017, 7(3), 233; https://doi.org/10.3390/app7030233
Received: 19 November 2016 / Revised: 15 February 2017 / Accepted: 23 February 2017 / Published: 1 March 2017
Cited by 3 | PDF Full-text (2644 KB) | HTML Full-text | XML Full-text
Abstract
The health conditions of complicated concrete structures require intrinsic cement-based sensors with a fast sensing response and high accuracy. In this paper, static, modal, harmonic, and transient dynamic analyses for the 0–3 type piezoelectric cement-based material with interdigitated electrodes (IEPCM) wafer were investigated [...] Read more.
The health conditions of complicated concrete structures require intrinsic cement-based sensors with a fast sensing response and high accuracy. In this paper, static, modal, harmonic, and transient dynamic analyses for the 0–3 type piezoelectric cement-based material with interdigitated electrodes (IEPCM) wafer were investigated using the ANSYS finite element numerical approach. Optimal design of the IEPCM was further implemented with electrode distance (P), electrode width (W), and wafer density (H) as the main parameters. Analysis results show that the maximum stress and strain in the x-polarization direction of the IEPCM are 2.6 and 3.19 times higher than that in the y-direction, respectively; there exists no repetition frequency phenomenon for the IEPCM. These indicate 0–3 type IEPCM possesses good orthotropic features, and lateral driving capacity notwithstanding, a hysteresis effect exists. Allowing for the wafer width (Wp) of 1 mm, the optimal design of the IEPCM wafer arrives at the best physical values of H, W and P are 6.2, 0.73 and 1.02 mm respectively, whereas the corresponding optimal volume is 10.9 mm3. Full article
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Open AccessArticle
Fuzzy Synthetic Evaluation of the Long-Term Health of Tunnel Structures
Appl. Sci. 2017, 7(2), 203; https://doi.org/10.3390/app7020203
Received: 3 December 2016 / Accepted: 13 February 2017 / Published: 17 February 2017
Cited by 5 | PDF Full-text (3554 KB) | HTML Full-text | XML Full-text
Abstract
A tunnel is a coupled system of the surrounding rock and the supporting structure. The health status of a tunnel structure is complex and is influenced by various factors. In addition, these factors are coupled and interacted with each other, which calls for [...] Read more.
A tunnel is a coupled system of the surrounding rock and the supporting structure. The health status of a tunnel structure is complex and is influenced by various factors. In addition, these factors are coupled and interacted with each other, which calls for the linguistic description of the tunnel safety level. In this paper, we describe the health status of a highway tunnel structure in terms of four levels: safe; basically safe; potentially unsafe and unsafe. Based on the analysis of the safety characteristics of the tunnel structure and its proposed safety level, this research develops a multi-level fuzzy synthetic evaluation model for the long-term safety evaluation system of a tunnel structure. The Cang Ling Tunnel, which has embedded sensors to measure the stress values of the secondary lining and the contact pressure, is used as an example to study the proposed method. The results show that the structure of the entire Cang Ling Tunnel is in almost a safe condition under the current conditions, which is consistent with the actual operational situation. Full article
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Open AccessArticle
Dielectric Characterization of Chinese Standard Concrete for Compressive Strength Evaluation
Appl. Sci. 2017, 7(2), 177; https://doi.org/10.3390/app7020177
Received: 27 December 2016 / Revised: 28 January 2017 / Accepted: 7 February 2017 / Published: 17 February 2017
Cited by 6 | PDF Full-text (3869 KB) | HTML Full-text | XML Full-text
Abstract
Dielectric characterization of concrete is essential for the wireless structural health monitoring (SHM) of concrete structures. Guo Biao (GB) concrete refers to the concrete mixed and cast in accordance with the Chinese standard. Currently, China is the largest producer and consumer of concrete [...] Read more.
Dielectric characterization of concrete is essential for the wireless structural health monitoring (SHM) of concrete structures. Guo Biao (GB) concrete refers to the concrete mixed and cast in accordance with the Chinese standard. Currently, China is the largest producer and consumer of concrete in the world. However, minimal attention has been paid to the dielectric properties of GB concrete. This paper presents the results of the dielectric constant of GB concrete, where three regression models have been used to present the measurement data from 10 MHz to 6 GHz. The objective is to provide a data set of nominal values of the dielectric constant for ordinary GB concrete. The final goal is to facilitate a compressive strength evaluation via the measured dielectric constant. Measurements of the dielectric constant and compressive strength for five types of ordinary concrete have been undertaken, after 28 days of curing. As the main contribution in this work, the correlation model between the compressive strength and dielectric constant of GB concrete is realized. Full article
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Open AccessArticle
Strain Transfer Analysis of a Clamped Fiber Bragg Grating Sensor
Appl. Sci. 2017, 7(2), 188; https://doi.org/10.3390/app7020188
Received: 25 November 2016 / Revised: 24 January 2017 / Accepted: 10 February 2017 / Published: 15 February 2017
Cited by 11 | PDF Full-text (1821 KB) | HTML Full-text | XML Full-text
Abstract
Clamped fiber Bragg grating (FBG) sensors have been widely applied in engineering strain measurements due to their advantages of high flexibility and efficiency. However, due to the existence of the interlayer, the strain measured by the encapsulated FBG sensor is not equal to [...] Read more.
Clamped fiber Bragg grating (FBG) sensors have been widely applied in engineering strain measurements due to their advantages of high flexibility and efficiency. However, due to the existence of the interlayer, the strain measured by the encapsulated FBG sensor is not equal to the strain of the host material, which causes strain measurement errors. In this paper, the strain transfer analysis of a clamped FBG sensor based on the shear-lag theory is conducted to improve the accuracy of strain measurements. A novel theoretical model for the axial strain distribution of a clamped FBG sensor is proposed. It is also discussed how the gauge ratio and interlayer thickness affect the strain transfer rate. The accuracy of the proposed theoretical model is verified by experimental tensile tests. The theoretical value of the strain transfer rate matches well with the tested value. Full article
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Open AccessArticle
Field Monitoring of Deformations and Internal Forces of Surrounding Rocks and Lining Structures in the Construction of the Gangkou Double-Arched Tunnel—A Case Study
Appl. Sci. 2017, 7(2), 169; https://doi.org/10.3390/app7020169
Received: 20 November 2016 / Revised: 29 January 2017 / Accepted: 5 February 2017 / Published: 11 February 2017
Cited by 6 | PDF Full-text (9745 KB) | HTML Full-text | XML Full-text
Abstract
Double-arched tunnel is a special and complex underground structure which needs to be monitored carefully during construction. Taking the Gangkou tunnel as the engineering background, this paper presents a case study of field monitoring of a representative double-arched tunnel. Typical cross sections were [...] Read more.
Double-arched tunnel is a special and complex underground structure which needs to be monitored carefully during construction. Taking the Gangkou tunnel as the engineering background, this paper presents a case study of field monitoring of a representative double-arched tunnel. Typical cross sections were chosen in each class of surrounding rock masses in the tunnel area and different types of sensors were embedded in designed locations, and the deformations and forces of both surrounding rocks and lining structures were monitored systematically. The dynamic evolution as well as the spatial distribution characteristics of the monitoring data including the internal displacements of surrounding rocks and the contact pressures between surrounding rocks and primary linings, the axial forces in rock bolts and the internal forces in both steel arches and secondary linings were analyzed. The monitoring and analysis results show that the deformations and forces of both surrounding rocks and lining structures are directly related to the construction procedures, geological conditions and locations in the double-arched tunnel. According to the results, some reasonable suggestions were provided for the improvement of the tunnel construction. This study will provide useful reference and guidance for the design, construction and monitoring of similar engineering projects in future. Full article
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Open AccessArticle
Remedial Modelling of Steel Bridges through Application of Analytical Hierarchy Process (AHP)
Appl. Sci. 2017, 7(2), 168; https://doi.org/10.3390/app7020168
Received: 22 November 2016 / Revised: 17 January 2017 / Accepted: 4 February 2017 / Published: 10 February 2017
Cited by 11 | PDF Full-text (3135 KB) | HTML Full-text | XML Full-text
Abstract
The deterioration and failure of steel bridges around the world is of growing concern for asset managers and bridge engineers due to aging, increasing volume of traffic and introduction of heavier vehicles. Hence, a model that considers these heuristics can be employed to [...] Read more.
The deterioration and failure of steel bridges around the world is of growing concern for asset managers and bridge engineers due to aging, increasing volume of traffic and introduction of heavier vehicles. Hence, a model that considers these heuristics can be employed to validate or challenge the practical engineering decisions. Moreover, in a time of increased litigation and economic unrest, engineers require a means of accountability to support their decisions. Maintenance, Repair and Rehabilitation (MR&R) of deteriorating bridge structures are considered as expensive actions for transportation agencies and the cost of error in decision making may aggravate problems related to infrastructure funding system. The subjective nature of decision making in this field could be replaced by the application of a Decision Support System (DSS) that supports asset managers through balanced consideration of multiple criteria. The main aim of this paper is to present the developed decision support system for asset management of steel bridges within acceptable limits of safety, functionality and sustainability. The Simplified Analytical Hierarchy Process S-AHP is applied as a multi criteria decision making technique. The model can serve as an integrated learning tool for novice engineers, or as an accountability tool for assurance to project stakeholders. Full article
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Open AccessArticle
A Two-Step Strategy for System Identification of Civil Structures for Structural Health Monitoring Using Wavelet Transform and Genetic Algorithms
Appl. Sci. 2017, 7(2), 111; https://doi.org/10.3390/app7020111
Received: 16 November 2016 / Revised: 12 January 2017 / Accepted: 17 January 2017 / Published: 24 January 2017
Cited by 10 | PDF Full-text (7327 KB) | HTML Full-text | XML Full-text
Abstract
Nowadays, the accurate identification of natural frequencies and damping ratios play an important role in smart civil engineering, since they can be used for seismic design, vibration control, and condition assessment, among others. To achieve it in practical way, it is required to [...] Read more.
Nowadays, the accurate identification of natural frequencies and damping ratios play an important role in smart civil engineering, since they can be used for seismic design, vibration control, and condition assessment, among others. To achieve it in practical way, it is required to instrument the structure and apply techniques which are able to deal with noise-corrupted and non-linear signals, as they are common features in real-life civil structures. In this article, a two-step strategy is proposed for performing accurate modal parameters identification in an automated manner. In the first step, it is obtained and decomposed the measured signals using the natural excitation technique and the synchrosqueezed wavelet transform, respectively. Then, the second step estimates the modal parameters by solving an optimization problem employing a genetic algorithm-based approach, where the micropopulation concept is used to improve the speed convergence as well as the accuracy of the estimated values. The accuracy and effectiveness of the proposal are tested using both the simulated response of a benchmark structure and the measurements of a real eight-story building. The obtained results show that the proposed strategy can estimate the modal parameters accurately, indicating than the proposal can be considered as an alternative to perform the abovementioned task. Full article
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Open AccessArticle
Strong Aftershock Study Based on Coulomb Stress Triggering—A Case Study on the 2016 Ecuador Mw 7.8 Earthquake
Appl. Sci. 2017, 7(1), 88; https://doi.org/10.3390/app7010088
Received: 8 December 2016 / Revised: 10 January 2017 / Accepted: 12 January 2017 / Published: 20 January 2017
Cited by 3 | PDF Full-text (1588 KB) | HTML Full-text | XML Full-text
Abstract
The 2016 Ecuador M 7.8 earthquake ruptured the subduction zone boundary between the Nazca plate and the South America plate. This M 7.8 earthquake may have promoted failure in the surrounding crust, where six M ≥ 6 aftershocks occurred following this mainshock. These [...] Read more.
The 2016 Ecuador M 7.8 earthquake ruptured the subduction zone boundary between the Nazca plate and the South America plate. This M 7.8 earthquake may have promoted failure in the surrounding crust, where six M ≥ 6 aftershocks occurred following this mainshock. These crustal ruptures were triggered by the high coulomb stress changes produced by the M 7.8 mainshock. Here, we investigate whether the six M ≥ 6 aftershocks are consistent with the positive coulomb stress region due to the mainshock. To explore the correlation between the mainshock and the aftershocks, we adopt a recently published high-quality finite fault model and focal mechanisms to study the coulomb stress triggers during the M 7.8 earthquake sequence. We compute the coulomb failure stress changes (ΔCFS) on both of the focal mechanism nodal planes. We compare the ΔCFS imparted by the M 7.8 mainshock on the subsequent aftershocks with the epicenter location of each aftershock. In addition, the shear stress, normal stress, and coulomb stress changes in the focal sources of each aftershock are also computed. Coulomb stress changes in the focal source for the six M ≥ 6 aftershocks are in the range of −2.17–7.564 bar. Only one computational result for the M 6.9 aftershock is negative; other results are positive. We found that the vast majority of the six M ≥ 6 aftershocks occurred in positive coulomb stress areas triggered by the M 7.8 mainshock. Our results suggest that the coulomb stress changes contributed to the development of the Ecuador M 7.8 earthquake sequence. Full article
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Open AccessArticle
Wind-Induced Fatigue Analysis of High-Rise Steel Structures Using Equivalent Structural Stress Method
Appl. Sci. 2017, 7(1), 71; https://doi.org/10.3390/app7010071
Received: 24 November 2016 / Revised: 26 December 2016 / Accepted: 5 January 2017 / Published: 20 January 2017
Cited by 7 | PDF Full-text (5520 KB) | HTML Full-text | XML Full-text
Abstract
Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on [...] Read more.
Welded beam-to-column connections of high-rise steel structures are susceptive to fatigue damage under wind loading. However, most fatigue assessments in the field of civil engineering are mainly based on nominal stress or hot spot stress theories, which has the disadvantage of dependence on the meshing styles and massive curves selected. To address this problem, in this paper, the equivalent structural stress method with advantages of mesh-insensitive quality and capability of unifying different stress-life curves (S-N curves) into one is introduced to the wind-induced fatigue assessment of a large-scale complicated high-rise steel structure. The multi-scale finite element model is established and the corresponding wind loading is simulated. Fatigue life assessments using equivalent structural stress method, hot spot stress method and nominal stress method are performed, and the results are verified and comparisons are made. The mesh-insensitive quality is also verified. The results show that the lateral weld toe of the butt weld connecting the beam flange plate and the column is the location where fatigue damage most likely happens. Nominal stress method considers fatigue assessment of welds in a more global way by averaging all the stress on the weld section while in equivalent structural stress method and hot spot method local stress concentration can be taken into account more precisely. Full article
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Open AccessArticle
Strength Correlation and Prediction of Engineered Cementitious Composites with Microwave Properties
Appl. Sci. 2017, 7(1), 35; https://doi.org/10.3390/app7010035
Received: 10 November 2016 / Revised: 7 December 2016 / Accepted: 14 December 2016 / Published: 27 December 2016
Cited by 4 | PDF Full-text (3342 KB) | HTML Full-text | XML Full-text
Abstract
This paper presents the results of microwave and mechanical measurements of engineered cementitious composites (ECCs) using a nondestructive microwave near-field detecting technique. The objective of this research is to investigate the correlations between effective conductance and compressive strength of ECCs at various curing [...] Read more.
This paper presents the results of microwave and mechanical measurements of engineered cementitious composites (ECCs) using a nondestructive microwave near-field detecting technique. The objective of this research is to investigate the correlations between effective conductance and compressive strength of ECCs at various curing ages under the influence of different initial water contents. Parallel measurements and regression analysis on compressive strength and microwave conductance were undertaken. It is shown that the strength evolution of ECCs can be accurately modeled and predicted by using microwave conductance at the early ages using bi-exponential functions. Compressive strength grows as a function of decreasing effective conductance, whereas the regression coefficients of the correlation models have a linear variation with water-to-binder ratios. These findings have highlighted the effectiveness of the microwave technique in detecting the variation of liquid phase morphology and pore structure. Full article
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Open AccessCommunication
Impedance-Based Non-Destructive Testing Method Combined with Unmanned Aerial Vehicle for Structural Health Monitoring of Civil Infrastructures
Appl. Sci. 2017, 7(1), 15; https://doi.org/10.3390/app7010015
Received: 15 November 2016 / Revised: 13 December 2016 / Accepted: 20 December 2016 / Published: 22 December 2016
Cited by 17 | PDF Full-text (2684 KB) | HTML Full-text | XML Full-text
Abstract
Unmanned aerial vehicles (UAVs), commonly known as drones, are a rising topic in remote sensing technologies for structural health monitoring. With technology advancement in cameras, the visual inspection method using drones is gaining much attention in the field of civil engineering. However, although [...] Read more.
Unmanned aerial vehicles (UAVs), commonly known as drones, are a rising topic in remote sensing technologies for structural health monitoring. With technology advancement in cameras, the visual inspection method using drones is gaining much attention in the field of civil engineering. However, although visual inspection methods are feasible for finding cracks in structures, the limitations of image processing for finding internal damage or small defects cannot be ignored. To overcome this problem, a possible application concept of UAV, combined with a vibration-based non-destructive health monitoring method, is proposed. The idea is for the drone to temporarily attach the piezoelectric transducer onto a specific region where excitation and data acquisition occurs simultaneously. This eliminates the need for a structure to be covered with hundreds of sensors for monitoring, as this concept uses a single piezoelectric transducer for monitoring a structure. The proposed work offers new areas of research by converging UAV with a vibration-based method, as associated problems are required to be solved. Full article
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Open AccessArticle
Sizing Subsurface Defects in Metallic Plates by Square Pulse Thermography Using an Oriented Gradient Map
Appl. Sci. 2016, 6(12), 389; https://doi.org/10.3390/app6120389
Received: 3 November 2016 / Revised: 22 November 2016 / Accepted: 22 November 2016 / Published: 5 December 2016
Cited by 3 | PDF Full-text (2493 KB) | HTML Full-text | XML Full-text
Abstract
We developed a new approach for sizing subsurface defects in the square pulse thermography of metallic plates by employing the oriented gradient of histograms. To size defects with high accuracies is still a challenge in infrared (IR) thermography today. Especially for blurry defects, [...] Read more.
We developed a new approach for sizing subsurface defects in the square pulse thermography of metallic plates by employing the oriented gradient of histograms. To size defects with high accuracies is still a challenge in infrared (IR) thermography today. Especially for blurry defects, accurate sizing of them is difficult with existing methods. The oriented gradient of histograms, which is used in the successful probability of boundary (Pb) contour detector in natural image processing literature, is employed in this work to improve the sizing accuracy in square pulse thermography. Experiments on a corroded steel plate with flat blind holes have verified the effectiveness of the proposed approach to size defects. Experimental results show that the proposed approach can size distinct and blurry defects with high accuracies. Comparison research is also implemented between the proposed approach and other sizing methods. The comparison results show that the proposed approach is superior to existing methods. Full article
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Open AccessArticle
A Novel Mechanical Fault Diagnosis Scheme Based on the Convex 1-D Second-Order Total Variation Denoising Algorithm
Appl. Sci. 2016, 6(12), 403; https://doi.org/10.3390/app6120403
Received: 26 October 2016 / Revised: 21 November 2016 / Accepted: 29 November 2016 / Published: 2 December 2016
Cited by 11 | PDF Full-text (5149 KB) | HTML Full-text | XML Full-text
Abstract
Convex 1-D first-order total variation (TV) denoising is an effective method for eliminating signal noise, which can be defined as convex optimization consisting of a quadratic data fidelity term and a non-convex regularization term. It not only ensures strict convex for optimization problems, [...] Read more.
Convex 1-D first-order total variation (TV) denoising is an effective method for eliminating signal noise, which can be defined as convex optimization consisting of a quadratic data fidelity term and a non-convex regularization term. It not only ensures strict convex for optimization problems, but also improves the sparseness of the total variation term by introducing the non-convex penalty function. The convex 1-D first-order total variation denoising method has greater superiority in recovering signals with flat regions. However, it often produces undesirable staircase artifacts. Moreover, actual denoising efficacy largely depends on the selection of the regularization parameter, which is utilized to adjust the weights between the fidelity term and total variation term. Using this, algorithms based on second-order total variation regularization and regularization parameter optimization selection are proposed in this paper. The parameter selection index is determined by the permutation entropy and cross-correlation coefficient to avoid the interference by human experience. This yields the convex 1-D second-order total variation denoising method based on the non-convex framework. Comparing with traditional wavelet denoising and first-order total variation denoising, the validity of the proposed method is verified by analyzing the numerical simulation signal and the vibration signal of fault bearing in practice. Full article
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Open AccessArticle
Parameter Identification Methods for Hyperelastic and Hyper-Viscoelastic Models
Appl. Sci. 2016, 6(12), 386; https://doi.org/10.3390/app6120386
Received: 9 October 2016 / Revised: 21 November 2016 / Accepted: 22 November 2016 / Published: 25 November 2016
Cited by 8 | PDF Full-text (1581 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, the Ogden model is employed to characterize the hyperelastic properties of rubber, and on the basis of a pattern search algorithm and the Levenberg-Marquardt algorithm, a professional method that can realize the comprehensive fitting of the uniaxial tension, biaxial tension, [...] Read more.
In this paper, the Ogden model is employed to characterize the hyperelastic properties of rubber, and on the basis of a pattern search algorithm and the Levenberg-Marquardt algorithm, a professional method that can realize the comprehensive fitting of the uniaxial tension, biaxial tension, planar tension, and simple shear experimental data of hyperelastic materials was developed. The experiment data from Treloar (1944) was fitted very well, and the determined parameters by using this method were proven correct and practical in the numerical verification in ANSYS. Then, the constitutive model of the hyper-viscoelastic materials combining the Ogden model with the generalized Maxwell model was explained in detail, and the parameter identification method was also proposed by using the pattern search method. Then, three groups of relaxation tests of uniaxial tension and four groups of simple shear tests with different loading velocities were conducted to obtain the corresponding virtual experiment data. After discussing the constraints and initial setting values for the undetermined parameters, these virtual data of different loading histories were respectively employed to identify the parameters in the hyper-elastic model, and the accuracy and the reliability of the estimated parameters were also verified in ANSYS. Full article
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Open AccessFeature PaperArticle
Cyclic Crack Monitoring of a Reinforced Concrete Column under Simulated Pseudo-Dynamic Loading Using Piezoceramic-Based Smart Aggregates
Appl. Sci. 2016, 6(11), 341; https://doi.org/10.3390/app6110341
Received: 21 September 2016 / Revised: 2 November 2016 / Accepted: 2 November 2016 / Published: 8 November 2016
Cited by 65 | PDF Full-text (3529 KB) | HTML Full-text | XML Full-text
Abstract
Structural health monitoring is an important aspect of maintenance for bridge columns in areas of high seismic activity. In this project, recently developed piezoceramic-based transducers, known as smart aggregates (SA), were utilized to perform structural health monitoring of a reinforced concrete (RC) bridge [...] Read more.
Structural health monitoring is an important aspect of maintenance for bridge columns in areas of high seismic activity. In this project, recently developed piezoceramic-based transducers, known as smart aggregates (SA), were utilized to perform structural health monitoring of a reinforced concrete (RC) bridge column subjected to pseudo-dynamic loading. The SA-based approach has been previously verified for static and dynamic loading but never for pseudo-dynamic loading. Based on the developed SAs, an active-sensing approach was developed to perform real-time health status evaluation of the RC column during the loading procedure. The existence of cracks attenuated the stress wave transmission energy during the loading procedure and reduced the amplitudes of the signal received by SA sensors. To detect the crack evolution and evaluate the damage severity, a wavelet packet-based structural damage index was developed. Experimental results verified the effectiveness of the SAs in structural health monitoring of the RC column under pseudo-dynamic loading. In addition to monitoring the general severity of the damage, the local structural damage indices show potential to report the cyclic crack open-close phenomenon subjected to the pseudo-dynamic loading. Full article
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Open AccessArticle
A Smart Washer for Bolt Looseness Monitoring Based on Piezoelectric Active Sensing Method
Appl. Sci. 2016, 6(11), 320; https://doi.org/10.3390/app6110320
Received: 21 September 2016 / Revised: 14 October 2016 / Accepted: 20 October 2016 / Published: 26 October 2016
Cited by 31 | PDF Full-text (2362 KB) | HTML Full-text | XML Full-text
Abstract
Piezoceramic based active sensing methods have been researched to monitor preload on bolt connections. However, there is a saturation problem involved with this type of method. The transmitted energy is sometimes saturated before the maximum preload which is due to it coming into [...] Read more.
Piezoceramic based active sensing methods have been researched to monitor preload on bolt connections. However, there is a saturation problem involved with this type of method. The transmitted energy is sometimes saturated before the maximum preload which is due to it coming into contact with flat surfaces. When it comes to flat contact surfaces, the true contact area will easily saturate with the preload. The design of a new type of bolt looseness monitoring sensor, a smart washer, is to mitigate the saturation problem. The smart washer is composed of two annular disks with contact surfaces that are machined into convex and concave respectively, to eliminate the complete flat contact surfaces and to reduce the saturation effect. One piezoelectric patch is bonded on the non-contact surface of each annular disk. These two mating annular disks form a smart washer. One of the two piezoelectric patches serves as an actuator to generate an ultrasonic wave that propagates through the contact surface; the other one serves as a sensor to detect the propagated waves. The wave energy propagated through the contact surface is proportional to the true contact area which is determined by the bolt preload. The time reversal method is used to extract the peak of the focused signal as the index of the transmission wave energy; then, the relationship between the signal peak and bolt preload is obtained. Experimental results show that the focused signal peak value changes with the bolt preload and presents an approximate linear relationship when the saturation problem is experienced. The proposed smart washer can monitor the full range of the rated preload. Full article
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Open AccessArticle
Bolt Looseness Detection Based on Piezoelectric Impedance Frequency Shift
Appl. Sci. 2016, 6(10), 298; https://doi.org/10.3390/app6100298
Received: 8 September 2016 / Revised: 8 October 2016 / Accepted: 11 October 2016 / Published: 15 October 2016
Cited by 34 | PDF Full-text (2652 KB) | HTML Full-text | XML Full-text
Abstract
In this paper, a piezoelectric impedance frequency shift method is developed to estimate the bolt preload for the detection of bolt looseness in engineering structures. An experimental device that allows the precision control of the axial preload force on a bolt is designed [...] Read more.
In this paper, a piezoelectric impedance frequency shift method is developed to estimate the bolt preload for the detection of bolt looseness in engineering structures. An experimental device that allows the precision control of the axial preload force on a bolt is designed and fabricated. A universal testing machine is used to preload accurately on the bolt in the experiments. Under different bolt preload conditions, the impedance analyzer measures the admittance (inverse of the impedance) signal of the PZT (Lead ZirconateTitanate) patches which are bonded on the bolt head. Firstly, a wide frequency band is swept to find a sensitive frequency band of the piezoelectric admittance with the imaginary part. Then in the sensitive frequency band, a specified peak frequency of the admittance signature is chosen to investigate the frequency shift with different bolt preloads. The relationship between the specified frequency shift and the bolt preload is established. The experimental results show that the specified peak frequency decreases as the bolt preload increases for both M16 and M12 bolts, and the frequency shift has a linear relationship with the preload on the bolt. The frequencies of the real and imaginary parts of the admittance signature have the same results. Therefore, the bolt preload can be determined by measuring the specified frequency shift and this method has a good application prospect. Full article
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Review

Jump to: Editorial, Research

Open AccessReview
A State of the Art Review of Modal-Based Damage Detection in Bridges: Development, Challenges, and Solutions
Appl. Sci. 2017, 7(5), 510; https://doi.org/10.3390/app7050510
Received: 1 April 2017 / Revised: 4 May 2017 / Accepted: 9 May 2017 / Published: 13 May 2017
Cited by 12 | PDF Full-text (316 KB) | HTML Full-text | XML Full-text
Abstract
Traditionally, damage identification techniques in bridges have focused on monitoring changes to modal-based Damage Sensitive Features (DSFs) due to their direct relationship with structural stiffness and their spatial information content. However, their progression to real-world applications has not been without its challenges and [...] Read more.
Traditionally, damage identification techniques in bridges have focused on monitoring changes to modal-based Damage Sensitive Features (DSFs) due to their direct relationship with structural stiffness and their spatial information content. However, their progression to real-world applications has not been without its challenges and shortcomings, mainly stemming from: (1) environmental and operational variations; (2) inefficient utilization of machine learning algorithms for damage detection; and (3) a general over-reliance on modal-based DSFs alone. The present paper provides an in-depth review of the development of modal-based DSFs and a synopsis of the challenges they face. The paper then sets out to addresses the highlighted challenges in terms of published advancements and alternatives from recent literature. Full article
Open AccessFeature PaperReview
The State-of-the-Art on Framework of Vibration-Based Structural Damage Identification for Decision Making
Appl. Sci. 2017, 7(5), 497; https://doi.org/10.3390/app7050497
Received: 10 April 2017 / Revised: 2 May 2017 / Accepted: 4 May 2017 / Published: 11 May 2017
Cited by 11 | PDF Full-text (525 KB) | HTML Full-text | XML Full-text
Abstract
Research on detecting structural damage at the earliest possible stage has been an interesting topic for decades. Among them, the vibration-based damage detection method as a global technique is especially pervasive. The present study reviewed the state-of-the-art on the framework of vibration-based damage [...] Read more.
Research on detecting structural damage at the earliest possible stage has been an interesting topic for decades. Among them, the vibration-based damage detection method as a global technique is especially pervasive. The present study reviewed the state-of-the-art on the framework of vibration-based damage identification in different levels including the prediction of the remaining useful life of structures and the decision making for proper actions. This framework consists of several major parts including the detection of damage occurrence using response-based methods, building reasonable structural models, selecting damage parameters and constructing objective functions with sensitivity analysis, adopting optimization techniques to solve the problem, predicting the remaining useful life of structures, and making decisions for the next actions. For each part, the commonly used methods were reviewed and the merits and drawbacks were summarized to give recommendations. This framework is aimed to guide the researchers and engineers to implement step by step the structure damage identification using vibration measurements. Finally, the future research work in this field is recommended. Full article
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