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Structural Health Monitoring for Civil Engineering Materials

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: closed (31 March 2021) | Viewed by 31004

Special Issue Editors

Department of Engineering Mechanics, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
Interests: analytical and applied mechanics; structural health monitoring; composite and smart materials; material characterization; sustainable concrete
Special Issues, Collections and Topics in MDPI journals
Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, China
Interests: theory and method of high-rise building structure design; structural vibration control; structural health monitoring; disaster prevention and mitigation for high-voltage transmission tower systems
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Civil engineering materials have evolved from conventional (such as concrete and steel) to new advanced and high performance (such as composites, high strength steel, and high performance concrete) materials over the last few decades. Considerable amounts of existing civil infrastructure constructed using conventional materials face aging and durability issues, as well as threats from both natural and manmade hazards. Modern and new civil infrastructures, though with better and improved performances, need integrated functionality to make them smarter and safer. Degradation, defect, damage, and even failure of civil infrastructure usually start at the local and material levels, and they, if not detected, assessed, and monitored, would eventually lead to catastrophe and huge economic losses. Thus, effective structural health monitoring for civil engineering materials is essential and critical for maintaining structural safety, sustainability, and resilience.

With significance of structural health monitoring for civil engineering, in general, and its materials, in particular, this Special Issue aims to publish peer-reviewed and open access papers that focus on analytical, experimental, and/or numerical investigations advancing the body of knowledge and its application in this important area of materials. The topics sought include, but are not limited to:

  • Dynamics-based methods for material damage detection and degradation assessment;
  • Diagnosis and prognosis techniques;
  • Mechanics for structural health monitoring;
  • Signal processing techniques;
  • Application of sensors, smart materials and wireless communication;
  • Monitoring of aging and durability as well as structural renewal;
  • Development of bio-inspired sensing or multifunctional materials;
  • Integrated smart material systems and structures;
  • Application of material monitoring techniques for civil infrastructure.

Prof. Pizhong Qiao
Prof. Hong-nan Li
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • civil engineering materials
  • monitoring of aging, degradation and durability
  • sensor technologies
  • diagnosis and prognosis techniques

Related Special Issue

Published Papers (13 papers)

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Research

20 pages, 2527 KiB  
Article
Influence of Hydrostatic Pressure and Cationic Type on the Diffusion Behavior of Chloride in Concrete
by Huanqiang Liu and Linhua Jiang
Materials 2021, 14(11), 2851; https://doi.org/10.3390/ma14112851 - 26 May 2021
Cited by 8 | Viewed by 2216
Abstract
The durability of the concrete in underground and marine engineering is affected by the underground and ocean environment. Chloride diffusion coefficient under hydrostatic pressure is a key parameter of concrete durability design under corresponding conditions. Therefore, this paper studies the diffusion behavior of [...] Read more.
The durability of the concrete in underground and marine engineering is affected by the underground and ocean environment. Chloride diffusion coefficient under hydrostatic pressure is a key parameter of concrete durability design under corresponding conditions. Therefore, this paper studies the diffusion behavior of chloride in different diffusion source solutions by experiment and simulation. Based on the experimental results, this paper proposes a new chloride diffusion model under the coupling effect of diffusion and convection. The interaction of ions and compounds in the diffusion source solutions, concrete pore fluid, and concrete material are considered in the new chloride diffusion model. The experimental results show that chloride diffusion rate is significantly affected by hydrostatic pressure, which increases with the increase of hydrostatic pressure. The chloride diffusion coefficient shows a certain difference in difference diffusion source solutions. The chloride diffusion coefficient in divalent cationic diffusion source solutions is the largest, the chloride diffusion coefficient in the divalent and monovalent cationic compound ones is in the middle, and the chloride diffusion coefficient in the monovalent cationic ones is the smallest. There is a linear relationship between the chloride diffusion coefficient and the hydrostatic pressure whether in single or combined cationic diffusion source solutions. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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16 pages, 4352 KiB  
Article
A New Method for Compaction Quality Evaluation of Asphalt Mixtures with the Intelligent Aggregate (IA)
by Chen Zhang and Hainian Wang
Materials 2021, 14(9), 2422; https://doi.org/10.3390/ma14092422 - 06 May 2021
Cited by 4 | Viewed by 1566
Abstract
To provide a new method for the evaluation of the compaction quality of asphalt mixture, a real-time data acquisition and processing system (RDAPS) for the motion state of aggregate with a small volume and high precision is developed. The system consists of an [...] Read more.
To provide a new method for the evaluation of the compaction quality of asphalt mixture, a real-time data acquisition and processing system (RDAPS) for the motion state of aggregate with a small volume and high precision is developed. The system consists of an intelligent aggregate (IA), analysis software and hardware equipment. The performance of the IA was tested by regarding data sensitivity, high-temperature resistance, and mechanical properties. A new evaluation method was proposed for evaluating the compaction quality of AC-25 and SMA-25 asphalt mixtures based on an IA. The results show that the best transmission baud rate for the IA was 9600 bps, and the corresponding signal transmission distance was 380 m. Only one IA was needed to complete the state data collection for the aggregate within the asphalt mixture in a circular area, with the IA layout point as the center of the circle and a radius of 5 m. The IA conducted reliable data transmission up to 200 °C; however, its compressive strength decreased with increasing temperature until reaching stability. Traditional aggregate could be replaced by an IA to withstand external forces and internal load transfer. Embedding an IA into AC-25 or SMA-25 asphalt mixtures did not have a significant impact on the original mechanical properties of the mixture. The effect of the gradation type of the asphalt mixture on the IA motion state was not significant. When the compaction degree met the specification requirements, the motion data of the IA did not reach a stable state, and the interlocking effect between aggregates in the asphalt mixture could be further optimized. An evaluation method is proposed based on the IA for the compaction quality of AC-25 and SMA-25 asphalt mixtures with the compaction degree as the main index and the spatial attitude angle and spatial acceleration of the IA as the auxiliary indexes. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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17 pages, 1742 KiB  
Article
Wavelet Scattering and Neural Networks for Railhead Defect Identification
by Yang Jin
Materials 2021, 14(8), 1957; https://doi.org/10.3390/ma14081957 - 14 Apr 2021
Cited by 7 | Viewed by 1794
Abstract
Accurate and automatic railhead inspection is crucial for the operational safety of railway systems. Deep learning on visual images is effective in the automatic detection of railhead defects, but either intensive data requirements or ignoring defect sizes reduce its applicability. This paper developed [...] Read more.
Accurate and automatic railhead inspection is crucial for the operational safety of railway systems. Deep learning on visual images is effective in the automatic detection of railhead defects, but either intensive data requirements or ignoring defect sizes reduce its applicability. This paper developed a machine learning framework based on wavelet scattering networks (WSNs) and neural networks (NNs) for identifying railhead defects. WSNs are functionally equivalent to deep convolutional neural networks while containing no parameters, thus suitable for non-intensive datasets. NNs can restore location and size information. The publicly available rail surface discrete defects (RSDD) datasets were analyzed, including 67 Type-I railhead images acquired from express tracks and 128 Type-II images captured from ordinary/heavy haul tracks. The ultimate validation accuracy reached 99.80% and 99.44%, respectively. WSNs can extract implicit signal features, and the support vector machine classifier can improve the learning accuracy of NNs by over 6%. Three criteria, namely the precision, recall, and F-measure, were calculated for comparison with the literature. At the pixel level, the developed approach achieved three criteria of around 90%, outperforming former methods. At the defect level, the recall rates reached 100%, indicating all labeled defects were identified. The precision rates were around 75%, affected by the insignificant misidentified speckles (smaller than 20 pixels). Nonetheless, the developed learning framework was effective in identifying railhead defects. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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23 pages, 5783 KiB  
Article
Non-Destructive Assessment of the Dynamic Elasticity Modulus of Eucalyptus nitens Timber Boards
by Alexander Opazo-Vega, Víctor Rosales-Garcés and Claudio Oyarzo-Vera
Materials 2021, 14(2), 269; https://doi.org/10.3390/ma14020269 - 07 Jan 2021
Cited by 5 | Viewed by 2218
Abstract
Eucalyptus nitens is a fast-growing wood species with a relevant presence in countries like Australia and Chile. The sustainable construction goals have driven the search of structural applications for Eucalyptus nitens; however, this process has been complicated due to the defects usually [...] Read more.
Eucalyptus nitens is a fast-growing wood species with a relevant presence in countries like Australia and Chile. The sustainable construction goals have driven the search of structural applications for Eucalyptus nitens; however, this process has been complicated due to the defects usually presented in these timber boards. This study aims to evaluate the dynamic elasticity modulus (Exd) of Eucalyptus nitens timber boards through non-destructive vibration-based tests. Thirty-six timber boards with different levels of knots and cracks were instrumented and tested in a simply supported condition by measuring longitudinal and transverse vibrations. In the first stage, the Exd was calculated globally through simplified normative formulas. Then, in a second stage, the local variability of the Exd was estimated using operational modal analysis (OMA), finite element numerical simulations (FEM), and regional sensitivity analysis (RSA). The positive correlation found between the global static modulus of elasticity and Exd suggests that non-destructive techniques could be used as a reliable and fast alternative for the assessment of bending stiffness. Finally, the proposed method to estimate the local variability of Exdt based on the combination of OMA, FEM, and RSA techniques was useful to improve the structural selection process of timber boards for lightweight social housing floors. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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30 pages, 41082 KiB  
Article
Non-Destructive Testing Mechanism for Pre-Stressed Steel Wire Using Acoustic Emission Monitoring
by Jothi Saravanan Thiyagarajan
Materials 2020, 13(21), 5029; https://doi.org/10.3390/ma13215029 - 07 Nov 2020
Cited by 10 | Viewed by 2317
Abstract
In this paper, the guided ultrasonic wave propagation characteristics in the axisymmetric pre-stressed viscoelastic waveguide for acoustic emission (AE) monitoring, using the semi-analytical finite element (SAFE) method, is studied broadly. For the numerical investigation, a single high-strength steel wire is considered. A comprehensive [...] Read more.
In this paper, the guided ultrasonic wave propagation characteristics in the axisymmetric pre-stressed viscoelastic waveguide for acoustic emission (AE) monitoring, using the semi-analytical finite element (SAFE) method, is studied broadly. For the numerical investigation, a single high-strength steel wire is considered. A comprehensive and in-depth study on the AE signal’s propagation characteristics is carried out based on the SAFE method. Both undamped and damped waveguides are considered for attaining SAFE solutions and presented in a detailed manner. The SAFE method for an axisymmetric cross-section in cylindrical coordinates analyzes the two main influencing factors of steel wire in a practical scenario: Material damping and initial tension. For the effect of initial stress, the calculation shows that the initial tensile stress can increase and decrease the energy velocity and attenuation factor of most modal waves above the cut-off frequency, and the effect is linear. Some longitudinal wave modes in the high-frequency region show their potential for AE monitoring as these modes have a low attenuation factor and small external surface vibration. By considering various states of initial stress in a damped waveguide, the effect of pre-stress on the dispersion characteristics is understood in a better manner. A non-destructive testing (NDT) mechanism for pre-stressed steel wire using AE monitoring is proposed for the health monitoring of structures. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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18 pages, 21650 KiB  
Article
Life Extension of Aged Jointed Plain Concrete Pavement through Remodeling Index–Based Analysis
by Haekook Jung, Yongjae Kim, Seungwon Kim, Cheolwoo Park and Jeong-Hee Nam
Materials 2020, 13(13), 2982; https://doi.org/10.3390/ma13132982 - 04 Jul 2020
Cited by 1 | Viewed by 1885
Abstract
As jointed plain concrete pavements (JPCP) age in South Korea, the cost of pavement maintenance is increasing annually. To extend the life of jointed concrete pavements through preventive maintenance, this study used 2017 pavement management system data to analyze the effects of traffic [...] Read more.
As jointed plain concrete pavements (JPCP) age in South Korea, the cost of pavement maintenance is increasing annually. To extend the life of jointed concrete pavements through preventive maintenance, this study used 2017 pavement management system data to analyze the effects of traffic volume, alkali–silica reaction (ASR) grade, age, smoothness, and damaged area on the remodeling index (RMI—a measure of expressway pavement condition). In addition, this study evaluates the final RMI as well as the corresponding pavement condition and change in RMI value after conducting preventive maintenance in lieu of resurfacing or overlaying. The results demonstrated that the effect of ASR grade increased as the RMI forecast year increased and that change in surface distress (△SD) increased with age (most intensively when the pavement was 15–20 years of age). Moreover, change in international roughness index (△IRI) increased with age and traffic volume (similarly within 15–20 years of pavement age). Hence, preventive maintenance is a must for sections with high traffic volume and age even if the RMI is low. Finally, performing repairs through preventive maintenance decreases the number of expressway sections requiring resurfacing and overlaying, thus extending the life of the concrete pavement. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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21 pages, 5577 KiB  
Article
Assessment of the Natural Radioactivity of Polish and Foreign Granites Used for Road and Lapidary Constructions in Poland
by Tomasz Drzymała, Aneta Łukaszek-Chmielewska, Sylwia Lewicka, Joanna Stec, Barbara Piotrowska, Krzysztof Isajenko and Paweł Lipiński
Materials 2020, 13(12), 2824; https://doi.org/10.3390/ma13122824 - 23 Jun 2020
Cited by 7 | Viewed by 2249
Abstract
The measurements of the specific activity of natural radioactive isotopes of radium (226Ra), thorium (232Th) and potassium (40K) in chosen samples of imported (China, Finland, Spain, India, Sweden) and Polish (Izerski, Karkonosze, Siedlimowicki, Strzegomski, Strzelinski) granites were [...] Read more.
The measurements of the specific activity of natural radioactive isotopes of radium (226Ra), thorium (232Th) and potassium (40K) in chosen samples of imported (China, Finland, Spain, India, Sweden) and Polish (Izerski, Karkonosze, Siedlimowicki, Strzegomski, Strzelinski) granites were performed. The measurements were carried out with 2 × 2” NaI(Tl) scintillation detector. The measured specific activity on natural radioactive isotopes were within the following ranges: 5.8–312 [Bq kg−1], 5.5–189 [Bq kg−1] and 109–1590 [Bq kg−1] for 226Ra, 232Th and 40K, respectively. Obtained concentrations of radioactive isotopes allowed to perform the analysis of the exposure of the humans from the ionizing radiation emitted by the granites. The determination of the exposure consisted in the calculation of absorbed gamma dose rate (D) [nGy h−1] for each sample, which fell in the range between 20 and 511 [nGy h−1], annual effective dose rate (AED) [mSv year−1] ranging between 0.10 and 2.50 [mSv year−1], radium equivalent activity (Raeq) [Bq kg−1] with values between 22 and 570 [Bq kg−1], external and internal hazard indices (Hex) and (Hin) falling in the ranges 0.06−1.53 and 0.08–2.41 respectively, as well as gamma (Iγ) and alpha (Iα), representative level indices with values 0.08–2.0 and 0.029–1.56, respectively. Moreover, obtained results were compared with the international standard values given by the European Commission (EC), the United Nations Scientific Committee on the Effects of Atomic Radiation given in UNSCEAR Reports, and the results of research from other laboratories. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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14 pages, 40301 KiB  
Article
A Method for Instant Estimation of the Temperature Experienced by Fire-Damaged Reinforced Concrete Structures Using Titanium
by Sang-Rak Sim and Dong-Woo Ryu
Materials 2020, 13(8), 1993; https://doi.org/10.3390/ma13081993 - 24 Apr 2020
Cited by 4 | Viewed by 2054
Abstract
When a concrete structure is exposed to fire, its structural safety is significantly compromised due to the spalling of members and scaling of concrete. In addition, its durability is substantially reduced due to certain chemical changes such as the dehydration of Ca(OH)2 [...] Read more.
When a concrete structure is exposed to fire, its structural safety is significantly compromised due to the spalling of members and scaling of concrete. In addition, its durability is substantially reduced due to certain chemical changes such as the dehydration of Ca(OH)2, the main hydration product of concrete, and the rehydration of CaO. Therefore, when fire damage occurs to a reinforced concrete (RC) building, rapid diagnosis and evaluation techniques are required for immediate repair and reinforcement, requiring a crucial step of quantitatively determining the heating temperature. This study aims to demonstrate a method of estimating the heating temperature experienced by fire damaged RC buildings. The experiments utilized two short RC column specimens with embedded titanium strips. The discoloration characteristics of titanium at high temperatures provided a quick, accurate, and simple mechanism for the estimation of the heating temperature by depth. Empirical equations were derived to estimate the heating temperature as a function of the discoloration characteristics of titanium. Thereafter, a comparison of this estimated temperature with the actual heating temperature measured using thermocouples revealed an average error of less than 20 °C, thereby demonstrating a significantly good correlation and an extremely high reliability of the proposed method. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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11 pages, 1625 KiB  
Article
Statics-Based Model-Free Damage Detection under Uncertainties Using Modal Interval Analysis
by Sheng-En Fang and Ji-Yuan Huang
Materials 2020, 13(7), 1567; https://doi.org/10.3390/ma13071567 - 28 Mar 2020
Cited by 4 | Viewed by 1700
Abstract
Deterministic damage detection methods often fail in practical applications due to ever-present uncertainties. Moreover, vibration-based model updating strategies are easily affected by measurement noises and could encounter ill-conditioning problems during inverse solutions. On this account, a model-free method has been proposed combining modal [...] Read more.
Deterministic damage detection methods often fail in practical applications due to ever-present uncertainties. Moreover, vibration-based model updating strategies are easily affected by measurement noises and could encounter ill-conditioning problems during inverse solutions. On this account, a model-free method has been proposed combining modal interval analyses with static measurements. Structural geometrical dimensions, material parameters and external loads are expressed by interval variables representing uncertainties. Mechanical formulas for static responses are then extended to their interval forms, which are subsequently solved using classic interval and modal interval analyses. The analytical interval envelopes of static responses such as deflections and strains are defined by the interval solutions, and damage can be detected when the measured responses intersect the envelopes. By this approach, potential damage can be found in a fast and rough way without any inverse solution process such as model updating. The proposed method has been verified against both numerical and experimental reinforced concrete beams whose strains were taken as the desirable responses. It was found that the strain envelopes provided by modal interval analysis were narrower than those by classic interval analysis. Modal interval analysis effectively avoids the phenomenon of interval overestimation. In addition, the intersection point also identifies the current external load, providing a loading alarm for structures. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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17 pages, 4910 KiB  
Article
Estimation of Heating Temperature for Fire-Damaged Concrete Structures Using Adaptive Neuro-Fuzzy Inference System
by Hyun Kang, Hae-Chang Cho, Seung-Ho Choi, Inwook Heo, Heung-Youl Kim and Kang Su Kim
Materials 2019, 12(23), 3964; https://doi.org/10.3390/ma12233964 - 29 Nov 2019
Cited by 17 | Viewed by 2131
Abstract
The structural performance of concrete structures subjected to fire is greatly influenced by the heating temperature. Therefore, an accurate estimation of the heating temperature is of vital importance for deriving a reasonable diagnosis and assessment of fire-damaged concrete structures. In current practice, various [...] Read more.
The structural performance of concrete structures subjected to fire is greatly influenced by the heating temperature. Therefore, an accurate estimation of the heating temperature is of vital importance for deriving a reasonable diagnosis and assessment of fire-damaged concrete structures. In current practice, various heating temperature estimation methods are used, however, each of these estimation methods has limitations in accuracy and faces disadvantages that depend on evaluators’ empirical judgments in the process of deriving diagnostic results from measured data. Therefore, in this study, a concrete heating test and a non-destructive test were carried out to estimate the heating temperatures of fire-damaged concrete, and a heating temperature estimation method using an adaptive neuro-fuzzy inference system (ANFIS) algorithm was proposed based on the results. A total of 73 datasets were randomly extracted from a total of 87 concrete heating test results and we used them in the data training process of the ANFIS algorithm; the remaining 14 datasets were used for verification. The proposed ANFIS algorithm model provided an accurate estimation of heating temperature. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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11 pages, 18417 KiB  
Article
Monolithic Structure-Optical Fiber Sensor with Temperature Compensation for Pressure Measurement
by Wenhua Wang, Xinlei Zhou, Weina Wu, Jihua Chen, Shenlong He, Weifeng Guo, Junbin Gao, Shaoxin Huang and Xuanhua Chen
Materials 2019, 12(4), 552; https://doi.org/10.3390/ma12040552 - 13 Feb 2019
Cited by 8 | Viewed by 3025
Abstract
In this paper, an optical fiber pressure sensor cascading a diaphragm-assisted Fabry-Perot interferometer (FPI) and a fiber Bragg grating (FBG) is proposed and demonstrated. The sensor comprises an optical fiber, a fused-silica ferrule, and a fused-silica diaphragm. We use a femtosecond laser firstly [...] Read more.
In this paper, an optical fiber pressure sensor cascading a diaphragm-assisted Fabry-Perot interferometer (FPI) and a fiber Bragg grating (FBG) is proposed and demonstrated. The sensor comprises an optical fiber, a fused-silica ferrule, and a fused-silica diaphragm. We use a femtosecond laser firstly to fabricate a pit on the end face of the ferrule and then investigate the laser heat conduction welding and deep penetration welding technology for manufacturing the seepage pressure sensor of the all-fused-silica material. We develop a sensor based on a monolithic structured FPI without adhesive bonding by means of all-laser-welding. The pressure characteristics of the sensor have good linearity at different temperatures. Also, the monolithic structured sensor possesses excellent resolution, hysteresis, and long-term stability. The environmental temperature obtained by the FBG is employed to compensate for the difference in seepage pressure at different temperatures, and the difference in seepage pressure responses at different temperatures is shown to be very small after temperature compensation. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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14 pages, 5074 KiB  
Article
Field Validation of a Magnetic Sensor to Monitor Borehole Deviation during Tunnel Excavation
by Fujian Tang, Jianzhou Yang, Hong-Nan Li, Fuqiang Liu, Ningbo Wang, Peng Jia and Yizheng Chen
Materials 2018, 11(9), 1511; https://doi.org/10.3390/ma11091511 - 23 Aug 2018
Viewed by 2923
Abstract
In this article, a magnetic sensor is proposed to monitor borehole deviation during tunnel excavation. It is made by piling four super-strong N42 NdFeB cylinder magnets and then encasing them in an aluminum alloy hollow cylinder. The distribution of the magnetic field produced [...] Read more.
In this article, a magnetic sensor is proposed to monitor borehole deviation during tunnel excavation. It is made by piling four super-strong N42 NdFeB cylinder magnets and then encasing them in an aluminum alloy hollow cylinder. The distribution of the magnetic field produced by the magnetic sensor and its summation with the geomagnetic field (GMF) in a global coordinate system are derived based on the theory of magnetic fields. An algorithm is developed to localize the position of the magnetic sensor. The effect of the GMF variation on the effective monitoring range of the magnetic sensor is also studied numerically. Field validation tests are conducted at Jinzhai Pumped-Storage hydroelectric power station, during the excavation of an inclined tunnel in Anhui Province of China. Test results show that the algorithm and the magnetic sensor are used successfully to detect the deviation of the borehole with an estimated error of approximately 0.5 m. The errors are mainly from the measurement errors of the coordinates, of both the test and the measurement points. The effective monitoring range of the magnetic sensor is dependent on the direction of the magnetic sensor as well as the variation of the GMF. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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17 pages, 5577 KiB  
Article
Multi-Scale Stress Wave Simulation for Aggregates Segregation Detection of Concrete Core in Circular CFST Coupled with PZT Patches
by Hongbing Chen, Bin Xu, Yilung Mo and Tianmin Zhou
Materials 2018, 11(7), 1223; https://doi.org/10.3390/ma11071223 - 17 Jul 2018
Cited by 17 | Viewed by 3600
Abstract
In this study, the numerical investigation of the detectability of concrete aggregate segregation in circular concrete-filled steel tubulars (CCFST) based on piezoelectric lead zirconate titanate (PZT) measurement is performed. The stress wave propagation in the concrete core of circular CCFST excited with a [...] Read more.
In this study, the numerical investigation of the detectability of concrete aggregate segregation in circular concrete-filled steel tubulars (CCFST) based on piezoelectric lead zirconate titanate (PZT) measurement is performed. The stress wave propagation in the concrete core of circular CCFST excited with a surface-mounted PZT actuator is studied with multi-scale and multi-physical field coupling analysis. The piezoelectric effect of PZT patches and its coupling effect with CFSTs are considered. Numerical concrete modeling technology is employed to construct the concrete core composed of randomly distributed aggregates with and without aggregate segregation at different levels, mortar, and an interfacial transition zone (ITZ). The effects of the random distribution of elliptical aggregates, aggregate segregation, and the existence of ITZ in the concrete core on the wave fields in the cross-section and the corresponding voltage response of the embedded PZT sensor are discussed. An evaluation index based on wavelet packet analysis on the output voltage response is defined, and its sensitivity to concrete aggregate segregation is systematically investigated. The multi-scale and multi-physics coupling simulation results indicate that concrete aggregate segregation in the concrete core of CFST members can be efficiently detected based on the stress wave measurement with a PZT sensor. Full article
(This article belongs to the Special Issue Structural Health Monitoring for Civil Engineering Materials)
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