Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Engineering and Materials".

Deadline for manuscript submissions: closed (31 July 2022) | Viewed by 29190

Special Issue Editor


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Guest Editor
College of Civil Engineering and Mechanics, Lanzhou University, Lanzhou 730000, China
Interests: smart optical fiber sensors and applied mechanics analysis; strain transfer analysis of multi-layered composites; smart monitoring, strengthening and assessment of FRP reinforced structures; design method of smart sensors for civil structures; full-scale monitoring, condition assessment and inverse design of pavements; structural health monitoring, damage identification and reinforcement
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Special Issue Information

Dear Colleagues,

Symmetry is an important concept during the mathematical and mechanical modeling of control systems in artificial intelligence domains. When sensors have been used to perceive the structural behavior, symmetry can be used to simplify the theoretical analysis on the strain transfer characteristics of multi-layered sensing models. Taking optical fiber sensor as an example, it can be used to measure strain and temperature information of engineering structures due to the unique advantages of high sensitivity, absolute measurement, stable physical and chemical properties, corrosion resistance, electromagnetic immunity, small size, light weight and easy integration of sensing networks. It is expected that smart optical fiber sensors can play an important role in promoting the development of artificial intelligence and intelligent manufacturing in engineering. How to use the measured information for the configuration of the structural performance and safety state is also an important issue. Applied mechanics analysis with symmetry considered is thus significant to scientifically explain the interaction between the smart optical fiber sensor and the monitored structure. For example, the discrete strains measured by the smart sensors can be adopted to configure the shape of the monitored structures with the mathematical algorithm. Based on the given shape, the health state of the structure can be assessed based on the mechanics analysis, which can provide instruction for the damage identification and rehabilitation. Please note that all submitted papers must be within the general scope of the Symmetry journal.

We are soliciting contributions (research and review articles) covering a broad range of topics on smart optical fiber sensors and applied mechanics analysis, including (though not limited to) the following keywords.

Prof. Dr. Huaping Wang
Guest Editor

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Keywords

  • smart optical fiber sensor
  • strain and temperature measurement
  • smart structural health monitoring system
  • structural information characterization
  • advanced testing solution
  • applied mechanics analysis
  • interfacial action between the smart sensor and the monitored structure
  • strain transfer analysis
  • microscopic analysis on the interfacial properties
  • symmetry of multi-layered sensing model

Published Papers (14 papers)

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Research

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15 pages, 5391 KiB  
Article
Stochastic Analysis of Train Running Safety on Bridge with Earthquake-Induced Irregularity under Aftershock
by Jincheng Tan, Ping Xiang, Han Zhao, Jian Yu, Bailong Ye and Delei Yang
Symmetry 2022, 14(10), 1998; https://doi.org/10.3390/sym14101998 - 23 Sep 2022
Cited by 10 | Viewed by 1362
Abstract
As a type of urban life project in China, bridges need a certain capacity of trains running safely after an earthquake to ensure and guarantee transportation on railway lines, post-disaster reconstruction and relief work. Since aftershocks may occur after the main shock, the [...] Read more.
As a type of urban life project in China, bridges need a certain capacity of trains running safely after an earthquake to ensure and guarantee transportation on railway lines, post-disaster reconstruction and relief work. Since aftershocks may occur after the main shock, the earthquake-induced irregularity and aftershock intensity are fully considered, based on the running safety index in the seismic design of bridges. However, there is a lack of research on the running safety of trains after an earthquake; it is mainly judged on experience, and lacks theoretical basis. In this paper, the established finite element model of a train bridge interaction system with symmetry was considered. The point estimation method (PEM) combined with moment expansion approximation (MEA) is used for random calculation of the Housner Intensity (HI). Furthermore, running safety indexes were analyzed and the running safety performance of a simply supported bridge with symmetry was assessed under a post-earthquake condition. Then the limit value, to ensure the traffic safety performance after an earthquake, is calculated based on stochastic analysis. The HI can be calculated with full consideration of the randomness of aftershock intensity and structural parameters. On this basis, a calculation method of the HI that considers the randomness of aftershock intensity is proposed. This study can be helpful for the performance-based design of symmetric railway structures under post-earthquake conditions. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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14 pages, 4884 KiB  
Article
Experimental Study on Bending Resistance of New Type Joint of Prestressed Concrete Pipe Pile
by Bo Wang, Lei Qi and Yongdong Yang
Symmetry 2022, 14(9), 1920; https://doi.org/10.3390/sym14091920 - 13 Sep 2022
Cited by 2 | Viewed by 1643
Abstract
In the field of PHC pile joints, it is important that prestressed high-strength concrete pipe piles are referred to as PHC pipe piles. In conventional hoops, bamboo-like joints protrude from the pile joint position at the surface of the pile. Driving the pile [...] Read more.
In the field of PHC pile joints, it is important that prestressed high-strength concrete pipe piles are referred to as PHC pipe piles. In conventional hoops, bamboo-like joints protrude from the pile joint position at the surface of the pile. Driving the pile in, disturbing the soil around the pile, and affecting the frictional resistance are serious issues. To address such issues, herein, a new type of clamping joint is proposed. A new method is presented to determine the size of the new joint that is flushed with the surface of the pile at the joint position. Bending resistance tests are conducted on four types of new joints for common pipe piles to study the deformation development process, bending bearing capacity, and damage characteristics of the new joints. Cracks are mainly distributed in the pure bending section and are approximately symmetrically distributed along both sides of the joint; there is no obvious cracking and damage in the joint until the pile cracks. Under the same bending moment, the deflection in the span of all specimens is greater than the deflection at the loading point. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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15 pages, 5173 KiB  
Article
Experimental Study on Dynamic Performance of Tubular Flange Grid-Type Dam under Impact Load
by Xiu-Li Wang, Yong Yao, Sai-Long Wang, Zhu-Jun Feng and Yun-Peng Chu
Symmetry 2022, 14(7), 1486; https://doi.org/10.3390/sym14071486 - 20 Jul 2022
Viewed by 1164
Abstract
As one of the most dangerous geological hazards in the world, debris flows can destroy trees and structures, break electrical, water, and gas lines, and disrupt bridges and roadways in a short period of time, threatening life and property. In particular, fast-moving large [...] Read more.
As one of the most dangerous geological hazards in the world, debris flows can destroy trees and structures, break electrical, water, and gas lines, and disrupt bridges and roadways in a short period of time, threatening life and property. In particular, fast-moving large boulders carried by debris-induced destructive impact loading can strike objects without warning. To resist impact loading caused by rocks in debris, this paper proposed an innovative grid-type debris dam (or Sabo dam) design composed of symmetrical cross-sections of steel tubular flange beams and columns. This paper studied the dynamic performance of the tubular flange columns under impact loading by conducting lab tests and numerical simulations. Moreover, the dynamic response of the grid-type debris dam was simulated under various loading conditions. Comparing three different types of columns with similar configurations under the same loading condition, the tubular flange column proposed in this research exhibits better performance in overall strain, displacement, acceleration, and bending conditions. Furthermore, the results also prove that the proposed structure has excellent interoperability and energy absorption capabilities. When increasing the testing impact load, the failure modes of the dam change from dent at the impact point to local buckling and total failure of the structure, which indicates that the structure has superior performance under impact loading. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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17 pages, 4377 KiB  
Article
Study on the Preparation and Performance of a Prefabricated Pervious-Cement-Based Concrete Pavement Slab
by Hong-Xia Zhai, Chao-Fan Li, Yun-Lin Liu, Yue Zhao, Yu-Zhao Tang, Hai-Bin Li and Ji-Yuan Zheng
Symmetry 2022, 14(7), 1295; https://doi.org/10.3390/sym14071295 - 22 Jun 2022
Cited by 1 | Viewed by 1653
Abstract
Based on the design of a prefabricated pervious composite cement concrete pavement slab, the interface properties and bending deformation properties of basalt pervious concrete (BPC) and PVA fiber base impervious concrete (PFBIC) composite specimens were studied. The effects of the different interfacial agents [...] Read more.
Based on the design of a prefabricated pervious composite cement concrete pavement slab, the interface properties and bending deformation properties of basalt pervious concrete (BPC) and PVA fiber base impervious concrete (PFBIC) composite specimens were studied. The effects of the different interfacial agents on the interfacial bonding performance were compared using a splitting tensile strength test and interfacial shear test. The deformation capacity of the composite specimens under bending load was tested using a three-point bending test, with the symmetry of the model considered and compared with the deformation capacity of the BPC specimen and PFBIC specimen. The results showed that the compressive strength of the BPC prepared using an orthogonal test reached 40.30 MPa, while the permeability coefficient was 2.41 mm/s. Different interface treatment processes determine the interface bonding properties. The best interface treatment method can induce the interface bonding strength to be higher than the strength of the BPC matrix itself, while the interface transition zone matrix will be denser without obvious microscopic defects. Under the bending tensile load, the ultimate bending stress reached 6.58 MPa and the maximum deflection in the midspan was 0.81 mm. As a protective layer, the PFBIC can alleviate the disadvantage of the insufficient strength of the BPC and can improve the bending ultimate bearing capacity of the BPC-PFBIC through its own stiffness. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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20 pages, 11925 KiB  
Article
Characterization of Engineering-Suitable Optical Fiber Sensors Packaged with Glass Fiber-Reinforced Polymers
by Tong Jiao, Chuhong Pu, Wenjing Xing, Tao Lv, Yuan Li, Huaping Wang and Jianping He
Symmetry 2022, 14(5), 973; https://doi.org/10.3390/sym14050973 - 10 May 2022
Cited by 4 | Viewed by 1898
Abstract
Glass fiber-reinforced polymer- (GFRP-) packaged optical fiber (OF) sensors are considered a promising engineering-suitable sensor for structural health monitoring. To date, some critical characteristics of the GFRP-packaged OF (GFRP-OF) sensors have not yet been thoroughly studied. This study aimed to systematically characterize the [...] Read more.
Glass fiber-reinforced polymer- (GFRP-) packaged optical fiber (OF) sensors are considered a promising engineering-suitable sensor for structural health monitoring. To date, some critical characteristics of the GFRP-packaged OF (GFRP-OF) sensors have not yet been thoroughly studied. This study aimed to systematically characterize the properties of the GFRP-OF sensors. Firstly, we proposed a dimension optimization method for GFRP-OF sensors by strain transfer theory, which is based on a symmetrical three-layered cylindrical model. Then, we experimentally investigated the properties of the GFRP-packaged fiber Bragg grating sensor and GFRP-packaged distributed optical fiber sensor, including their mechanical properties, strain/temperature sensing performance, fatigue resistance, and corrosion resistance. The experimental results showed that the shear bearing capacity of GFRP-OF sensors was more than 120 times larger than that of the other three coated OF sensors, indicating that GFRP dramatically enhanced the robustness of the OF sensor. The GFRP–OF sensors also feature excellent strain and temperature sensing performance with high linearity and repeatability. The results also demonstrated that the GFRP–OF sensors have good fatigue properties with absolute fluctuations of strain sensitivity coefficients throughout the fatigue cycles within 0.02 pm/με; repeatability error did not exceed 0.5%, and nonlinear errors were less than 2%. A case study presented in the last section also illustrates the effectiveness of the GFRP-OF sensor in a field application. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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17 pages, 6745 KiB  
Article
Propagation Prediction of Body Waves in Fluid-Saturated Soils with Flow-Independent Viscosity
by Bo Wang, Xingyuan Zhang and Bo Sun
Symmetry 2022, 14(2), 408; https://doi.org/10.3390/sym14020408 - 18 Feb 2022
Cited by 3 | Viewed by 1424
Abstract
A systematic study of wave theory in thermoviscoelastic soil is essential for engineering applications such as geophysical exploration. In the present work, the influences of flow-independent viscosity of the soil skeleton and the thermal effect on elastic waves are considered, and the propagation [...] Read more.
A systematic study of wave theory in thermoviscoelastic soil is essential for engineering applications such as geophysical exploration. In the present work, the influences of flow-independent viscosity of the soil skeleton and the thermal effect on elastic waves are considered, and the propagation behaviors of body waves in thermoviscoelastic saturated soil are investigated. Firstly, the thermoviscoelastic dynamic coupling model of saturated soil were established by employing the Biot model, the generalized thermoelastic theory, and the Kelvin–Voigt linear viscoelastic model. Secondly, the dispersion equations of body waves in thermoviscoelastic saturated soil were theoretically derived with structural symmetry considered. Finally, the variations of wave velocity and the attenuation coefficient of the body waves with the thermophysical parameters are discussed. The results revealed that the enhancement of the relaxation time of soil caused an increase of wave velocity and the attenuation coefficient of P1, P2, and S waves, and a decrease of the wave velocity and attenuation coefficient of the thermal wave. Different ranges of the permeability coefficient and frequency have different effects on the P1, P2, and S waves. The variation of thermal conductivity and the phase-lags of heat flux and temperature gradient only affect the thermal wave. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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20 pages, 10757 KiB  
Article
Axial Compression Behavior of Symmetrical Full-Scale Concrete Filled Double Skin Steel Tube Stub Columns
by Wen Bai, Yunhao Li, Jing Ji, Yuchen Liu, Lei Zhang, Ruili Wang, Liangqin Jiang and Lingjie He
Symmetry 2022, 14(2), 223; https://doi.org/10.3390/sym14020223 - 24 Jan 2022
Cited by 5 | Viewed by 2282
Abstract
To investigate the bearing behavior of symmetrical full-scale different strength concrete filled double skin steel tube (CFDST) stub columns, 19 full-scale specimens were designed, considering the slenderness ratio (λ); the compression strength of core concrete and sandwich concrete (fcki [...] Read more.
To investigate the bearing behavior of symmetrical full-scale different strength concrete filled double skin steel tube (CFDST) stub columns, 19 full-scale specimens were designed, considering the slenderness ratio (λ); the compression strength of core concrete and sandwich concrete (fcki, fcko), the thickness of the inner and outer steel tubes (ti, to); the diameter of inner and outer steel tubes (Di, Do); and the tensile strength of the inner and outer steel tubes (fyki, fyko) as the main parameters. Nonlinear constitutive models for concrete considering constraint effect were adopted, and a finite element (FE) model was established using ABAQUS software. By comparing the results between simulations and experiments, the rationality of the modeling method was verified. Based on the FE model, the parameter analysis for CFDST columns were conducted, and the force mechanism, stress distribution, and deformation process were analyzed. The results showed that the axial compression bearing capacity (Nsu) increased significantly with an increase in fcki, to, Do, and fcko, while Nsu decreased gradually with an increase in λ. Finally, according to the calculated results of the specimens, the calculation formula for Nsu of full-scale composite columns was statistically regressed using 1stOpt software and showed a good agreement with the FE. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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26 pages, 21160 KiB  
Article
Hysteretic Behavior on Asymmetrical Composite Joints with Concrete-Filled Steel Tube Columns and Unequal High Steel Beams
by Jing Ji, Wen Zeng, Liangqin Jiang, Wen Bai, Hongguo Ren, Qingru Chai, Lei Zhang, Hongtao Wang, Yunhao Li and Lingjie He
Symmetry 2021, 13(12), 2381; https://doi.org/10.3390/sym13122381 - 10 Dec 2021
Cited by 6 | Viewed by 2068
Abstract
In order to acquire the hysteretic behavior of the asymmetrical composite joints with concrete-filled steel tube (CFST) columns and unequal high steel beams, 36 full-scale composite joints were designed, and the CFST hoop coefficient (ξ), axial compression ratio (n0 [...] Read more.
In order to acquire the hysteretic behavior of the asymmetrical composite joints with concrete-filled steel tube (CFST) columns and unequal high steel beams, 36 full-scale composite joints were designed, and the CFST hoop coefficient (ξ), axial compression ratio (n0), concrete cube compressive strength (fcuk), steel tube strength (fyk), beam, and column section size were taken as the main control parameters. Based on nonlinear constitutive models of concrete and the double broken-line stress-hardening constitutive model of steel, and by introducing the symmetric contact element and multi-point constraint (MPC), reduced-scale composite joints were simulated by ABAQUS software. By comparing with the test curves, the rationality of the modeling method was verified. The influence of various parameters on the seismic performance of the full-scale asymmetrical composite joints was investigated. The results show that with the increasing of fcuk, the peak load (Pmax) and ductility of the specimens gradually increased. With the increasing of n0, the Pmax of the specimens gradually increases firstly and then gradually decreases after reaching a peak point. The composite joints have good energy dissipation capacity and the characteristic of stiffness degradation. The oblique struts force mechanism in the full-scale asymmetrical composite joint domain is proposed. By introducing influence coefficients (ξ1 and ξ2), the expression of shear bearing capacity of composite joints is obtained by statistical regression, which can provide theoretical support for the seismic design of asymmetrical composite joints. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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14 pages, 3139 KiB  
Article
Lateral-Torsional Buckling Analysis for Doubly Symmetric Tubular Flange Composite Beams with Lateral Bracing under Concentrated Load
by Yingchun Liu, Ziwen He, Wenfu Zhang, Jing Ji, Yuchen Liu, Zizhen Wang, Ruili Wang, Kailin Yang and Zhichao Zhang
Symmetry 2021, 13(12), 2328; https://doi.org/10.3390/sym13122328 - 5 Dec 2021
Cited by 1 | Viewed by 2211
Abstract
Tubular flange composite beams are increasingly applied in modern bridge structures. In order to investigate the overall stability behavior of doubly symmetric tubular flange composite beams with lateral bracing under concentrated load, the analysis of elastic lateral-torsional buckling is conducted by the energy [...] Read more.
Tubular flange composite beams are increasingly applied in modern bridge structures. In order to investigate the overall stability behavior of doubly symmetric tubular flange composite beams with lateral bracing under concentrated load, the analysis of elastic lateral-torsional buckling is conducted by the energy variation method. The analytical solution of critical moment of doubly symmetric tubular flange composite beams with lateral bracing is obtained. Meanwhile, the simplified calculation formula of critical moment is fitted by 1stOpt software based on 26,000 groups of data, and the accuracy is verified by the finite element method. It is found that, the critical moment rises obviously with increasing lateral bracing stiffness, and adding lateral bracing to doubly symmetric tubular flange composite beams is beneficial to improve the overall stability in engineering practice. Finally, the influence of several parameters including concrete strength, span, steel ratio of flange and height-thickness ratio of web are studied. The results show that the concrete strength and the web height-thickness ratio have a weak influence on critical moment of elastic lateral-torsional buckling, while the influence of span-depth ratio and flange steel ratio is very significant. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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21 pages, 30791 KiB  
Article
The Structural Performance of CFRP Composite Plates Assembled with Fiber Bragg Grating Sensors
by Hua-Ping Wang, Hao Chen, Cong Chen, Hu-Yuan Zhang, Hao Jiang, Tao Song and Si-Yuan Feng
Symmetry 2021, 13(9), 1631; https://doi.org/10.3390/sym13091631 - 5 Sep 2021
Cited by 10 | Viewed by 2166
Abstract
Carbon fiber reinforced polymer (CFRP) composites have been extensively used in airframes, train bodies, and engine blades for their properties of high strength, low weight, and good stability. The in-service structural performance of CFRP composites is always an important point to be investigated [...] Read more.
Carbon fiber reinforced polymer (CFRP) composites have been extensively used in airframes, train bodies, and engine blades for their properties of high strength, low weight, and good stability. The in-service structural performance of CFRP composites is always an important point to be investigated for its influence on structural safety. For this reason, CFRP composite plates assembled with fiber Bragg grating (FBG) sensors were developed, and the in-service structural characteristics of the CFRP plates were interpreted by FBG signals measured through time. A theoretical analysis supported by a numerical method has been provided. Experimental testing was conducted to check the proposed sensing technique for the dynamic response identification of the CFRP plate. The curing process of the bilayer CFRP plated inserted with FBGs in series was also explored. The results showed that the surface-attached FBGs in series could accurately characterize the dynamic response of the CFRP plate, and a good agreement between the numerical and testing results was observed. The strain and temperature distributions during the curing process of the bilayer plate indicated that the in-service structural performance of bilayer CFRP plates can be configured by the assembled FBG sensors. This study can support the structural health monitoring of projects by using CFRP composites. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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14 pages, 3195 KiB  
Article
Early Weak Fault Diagnosis of Rolling Bearings Based on Fiber Bragg Grating Sensing Monitoring
by Xinxin Chen, Yali Jiang, Boning Zhou, Hui Zhan, Hongwei Li, Guohui Lyu and Shuli Sun
Symmetry 2021, 13(8), 1473; https://doi.org/10.3390/sym13081473 - 11 Aug 2021
Cited by 3 | Viewed by 1914
Abstract
Aiming at the problems of weak dynamic response and difficulty in diagnosis of early damage of rolling bearings, a diagnosis method for early damage of rolling bearings is proposed. Taking radial rolling bearings as the main research object, the load symmetric structure of [...] Read more.
Aiming at the problems of weak dynamic response and difficulty in diagnosis of early damage of rolling bearings, a diagnosis method for early damage of rolling bearings is proposed. Taking radial rolling bearings as the main research object, the load symmetric structure of deep groove ball bearings is analyzed. Based on the mechanical second-order system theory, the sensor monitoring structure is constructed. The generalized resonance principle is used to identify weak signals, and the fiber Bragg grating is used for signal sensing. The signal is obtained through the fiber Bragg grating high-speed demodulator. When a continuous periodic generalized resonance wave appears in the amplitude–frequency analysis of the signal, and there is a high-frequency resonance frequency, it can be proved that the bearing is faulty. The diagnosis method can effectively avoid the interference of low-frequency signals, the frequency spectrum is pure and there is no electromagnetic interference. It fully shows that the fiber Bragg grating sensor is suitable for the monitoring and diagnosis of the early weak fault of the bearing. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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20 pages, 5338 KiB  
Article
Improved Analytical Method for Interfacial-Slip Control Design of Steel–Concrete Composite Structures
by Hua-Ping Wang, Tao Song, Jian-Wei Yan, Ping Xiang, Si-Yuan Feng and David Hui
Symmetry 2021, 13(7), 1225; https://doi.org/10.3390/sym13071225 - 8 Jul 2021
Cited by 8 | Viewed by 2262
Abstract
Interfacial performance is quite significant for maintaining the structural performance of steel–concrete composite structures. Quantitative assessment on the interfacial effect is critical. For this reason, theoretical investigation on the interfacial interaction of steel–concrete composites was performed, with the symmetry of the model considered. [...] Read more.
Interfacial performance is quite significant for maintaining the structural performance of steel–concrete composite structures. Quantitative assessment on the interfacial effect is critical. For this reason, theoretical investigation on the interfacial interaction of steel–concrete composites was performed, with the symmetry of the model considered. Influence of interfacial slip on the mechanical properties of the composites was considered. Analytical solutions of the interfacial slip and strain were provided. The accuracy of the predictions from the improved analytical model was validated by comparing them against the results from experimental and numerical studies. The influence of design parameters of the composite members on the interfacial effect was discussed. The proposed analytical model was also employed to assess the effect of the bond developing at the interface between concrete and steel on the deformation exhibited by simple composite structural forms (e.g., beams). Through the analysis, the priority design parameters of the composite structures are determined for controlling the level of interfacial slip in order to achieve optimum bearing capacity. Different to commonly used energy methods, numerical methods and finite element methods, the study provides a simple and straightforward analytical solution for describing the interfacial interaction of composite structures for the first time, which can act as scientific instruction for the interfacial slip control of composite materials and structures. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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7 pages, 2522 KiB  
Article
Measurement Improvement of Distributed Optical Fiber Sensor via Lorenz Local Single Peak Fitting Algorithm
by Bin Liu, Jianping He, Shihai Zhang, Yinping Zhang, Jianan Yu and Xiaoxue Wang
Symmetry 2021, 13(7), 1166; https://doi.org/10.3390/sym13071166 - 29 Jun 2021
Viewed by 1376
Abstract
Brillouin frequency shift (BFS) of distributed optical fiber sensor is extracted from the Brillouin gain spectrum (BGS), which is often characterized by Lorenz type. However, in the case of complex stress and optical fiber self damage, the BGS will deviate from Lorenz type [...] Read more.
Brillouin frequency shift (BFS) of distributed optical fiber sensor is extracted from the Brillouin gain spectrum (BGS), which is often characterized by Lorenz type. However, in the case of complex stress and optical fiber self damage, the BGS will deviate from Lorenz type and be asymmetric, which leads to the extraction error of BFS. In order to enhance the extraction accuracy of BFS, the Lorenz local single peak fitting algorithm was developed to fit the Brillouin gain spectrum curve, which can make the BSG symmetrical with respect to the Brillouin center frequency shift. One temperature test of a fiber-reinforced polymer (FRP) packaged sensor whose BSG curve is asymmetric was conducted to verify the idea. The results show that the local region curve of BSG processed by the developed algorithm has good symmetry, and the temperature measurement accuracy obtained by the developed algorithm is higher than that directly measured by demodulation equipment. Comparison with the reference temperature, the relative measurement error measured by the developed algorithm and BOTDA are within 4% and 8%, respectively. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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Review

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18 pages, 5765 KiB  
Review
Optical Fiber Sensors for Monitoring Railway Infrastructures: A Review towards Smart Concept
by Yung William Sasy Chan, Hua-Ping Wang and Ping Xiang
Symmetry 2021, 13(12), 2251; https://doi.org/10.3390/sym13122251 - 25 Nov 2021
Cited by 27 | Viewed by 3850
Abstract
Railway infrastructures have played a critical role to ensure the continuity of goods and passenger transportation in China. Under extreme loading and environmental conditions, railway structures are vulnerable to deterioration and failure, leading to the interruption of the whole transportation system. Several techniques [...] Read more.
Railway infrastructures have played a critical role to ensure the continuity of goods and passenger transportation in China. Under extreme loading and environmental conditions, railway structures are vulnerable to deterioration and failure, leading to the interruption of the whole transportation system. Several techniques have been used for the health monitoring of railway structures. Optical fiber sensors are the widely recognized technique due to their inherent advantages such as high sensitivity, anti-electromagnetic interference, light weight, tiny size, corrosion resistance, and easy integration and network configuration. This paper provides a state-of-the-art of optical fiber sensing technologies and their practical application in railway infrastructures. In addition, the strain transfer analysis of optical fiber sensors is described for parameter reflection. A smart concept for artificial intelligence contribution is also declared. Finally, existing and future prospects on smart concept-based optical fiber sensors for railway infrastructure are discussed. The study can provide useful guidance to understand the problems in artificial intelligence which contributed to the Structural Health Monitoring system of railway structures. Full article
(This article belongs to the Special Issue Symmetry in Applied Mechanics Analysis on Smart Optical Fiber Sensors)
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