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Advances in FRP Composites: Applications, Sensing, and Monitoring
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Advances in FRP Composites: Applications, Sensing, and Monitoring

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Physical Sensors".

Deadline for manuscript submissions: closed (31 December 2018) | Viewed by 69052

Special Issue Editors

Prof. Dr. Yun Lai Zhou

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Guest Editor
State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Interests: structural health monitoring; damage identification; bridge optimization; model updating; fracture mechanics
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Magd Abdel Wahab

E-Mail Website
Guest Editor
Laboratory Soete, Faculty of Engineering and Architecture, Ghent University, Technologiepark Zwijnaarde 903, B-9052 Zwijnaarde, Belgium
Interests: computational mechanics; fracture mechanics; damage mechanics; finite element analysis; fatigue of materials; fretting fatigue; fretting wear; durability; dynamics and vibration of structures
Special Issues, Collections and Topics in MDPI journals
Dr. Francisco Javier Cara Cañas

E-Mail Website
Guest Editor
Laboratory of Statistics, ETS Ingenieros Industriales, Universidad Politécnica de Madrid, Spain
Interests: analysis of modal operations; EM algorithms
Special Issues, Collections and Topics in MDPI journals
Dr. Cheng Jiang

E-Mail Website
Guest Editor
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China
Interests: Structural Engineering; Civil Engineering
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fiber reinforced polymer (FRP) composites have observed increasingly wide applications in civil engineering, mechanical engineering, aerospace engineering, and so on, owing to their advantages, such as high strength-to-weight and stiffness-to-weight ratios, in surpassing the limitations of conventional materials. FRP has been of core interest for scientists and engineers in designing and constructing new buildings, and in the maintenance of aged infrastructure, mechanical components, and so on. Although FRP has served in various fields, it lacks the full understanding of FRP in its whole service cycle. The degradation inspection and monitoring of FRP composite structures still requires further investigation, and the failure criterions as well, in particular for the complex structures integrated with FRP composite components.

This Special Issue aims to explore FRP composites via two perspectives: FRP composites applications, such as construction and sensing, inspection and monitoring, in particular, the recent advances in both industrial applications and sensing techniques for inspection and monitoring of FRP composites degradation. Rather than concentrating on the material level, this Special Issue focuses on the structural level and application field of FRP composites, which shall include the applications of FRP composites in infrastructures, tall buildings, long span bridges, airplanes and so on. This Special Issue expects the investigations related to FRP composites from mechanical engineering, civil engineering, numerical studies, and so on.

This Special Issue expects to publish high-quality studies in terms of FRP composites applications and the sensing, inspection and monitoring, as well as reviews summarizing the advances in recent years. Original, high-quality contributions that are not published elsewhere are the target of this Special Issue.

  • Potential topics include but are not limited to the following:
  • Advances in sensing techniques for FRP composite structures
  • Novel inspection methods for FRP composite structures
  • Structural health monitoring for FRP composite structures
  • Recent advances in designs, manufacture and applications of FRP
  • Durability, fatigue performance of FRP composite structures
  • Advanced sensing systems in FRP composites
  • Embedded sensing system in FRP composites
Dr. Yun Lai Zhou
Dr. Magd Abdel Wahab
Dr. Francisco Javier Cañas Cara
Dr. Cheng Jiang
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. Sensors 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

  • FRP
  • Composite structures
  • Structural health monitoring
  • Damage identification
  • Durability
  • Fatigue

Published Papers (16 papers)

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Research

17 pages, 3575 KiB  
Article
Flexural Capacity and Deflection of Fiber-Reinforced Lightweight Aggregate Concrete Beams Reinforced with GFRP Bars
by Xi Liu, Yijia Sun and Tao Wu
Sensors 2019, 19(4), 873; https://doi.org/10.3390/s19040873 - 20 Feb 2019
Cited by 12 | Viewed by 3758
Abstract
Adding fibers is highly effective to enhance the deflection and ductility of fiber-reinforced polymer (FRP)-reinforced beams. In this study, the stress and strain conditions of FRP-reinforced lightweight aggregate concrete (LWC) beams with and without fibers at ultimate load level were specified. Based on [...] Read more.
Adding fibers is highly effective to enhance the deflection and ductility of fiber-reinforced polymer (FRP)-reinforced beams. In this study, the stress and strain conditions of FRP-reinforced lightweight aggregate concrete (LWC) beams with and without fibers at ultimate load level were specified. Based on the sectional analyses, alternative equations to predict the balanced reinforcement ratio and flexural capacity for beams failed by balanced failure and concrete crushing were established. A rational equation for estimating the short-term stiffness of FRP–LWC beams at service-load levels was suggested based on Zhu’s model. In addition, the contribution of the steel fibers on the short-term stiffness was quantified incorporating the effects of FRP reinforcement ratio. The proposed short-term stiffness model was validated with measured deflections from an experimental database for fiber-reinforced normal weight concrete (FNWC) beams reinforced with FRP bars. Furthermore, six glass fiber-reinforced polymer (GFRP)-reinforced LWC beams with and without steel fibers were tested under four-point bending. Based on the test results, the proposed models and procedures according to current design codes ACI 440.1R, ISIS-M03, GB 50608, and CSA S806 were linked together by comparing their predictions. The results showed that increasing the reinforcement ratio and adding steel fibers decreased the strain of the FRP bars. The flexural capacity of the LWC beams with and without steel fibers was generally underestimated by the design codes, while the proposed model provided accurate ultimate moment predictions. Moreover, the proposed short-term stiffness model yielded reasonable estimations of deflection for both steel fiber-reinforced lightweight aggregate concrete (SFLWC) and FNWC beams. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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17 pages, 7156 KiB  
Article
Improved Current Sensor for Water Diffusion Testing of Composite Insulators
by Zhonghao Zhang, Fanghui Yin, Liming Wang and Hongwei Mei
Sensors 2019, 19(4), 778; https://doi.org/10.3390/s19040778 - 14 Feb 2019
Cited by 1 | Viewed by 2977
Abstract
An improved current sensor aimed at measuring currents of different parts in composite insulator samples was proposed. Conventional current sensors used in water diffusion tests aim to examine the performance of composite insulators, however, it is difficult for the conventional current sensors to [...] Read more.
An improved current sensor aimed at measuring currents of different parts in composite insulator samples was proposed. Conventional current sensors used in water diffusion tests aim to examine the performance of composite insulators, however, it is difficult for the conventional current sensors to locate the defects. Thus, we designed a new electrode structure to measure the currents of different components in short samples of composite insulators. Based on a finite analysis method, the influence of relative permittivity and conductivity on the current was analyzed. New samples with different interfaces and samples after operation were tested using the new and conventional current sensors. The performance of a certain part in short samples can be diagnosed by analyzing the current and phase information extracted from the test results. By comparing the test results of new and traditional current sensors, it was proved that the new electrode structure is more effective in locating the defects of insulators. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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18 pages, 6479 KiB  
Article
Axial Compression Behaviours of Pultruded GFRP–Wood Composite Columns
by Yujun Qi, Lei Xie, Yu Bai, Weiqing Liu and Hai Fang
Sensors 2019, 19(4), 755; https://doi.org/10.3390/s19040755 - 13 Feb 2019
Cited by 15 | Viewed by 3500
Abstract
An innovative pultruded fiber reinforced polymer (FRP)–wood composite (PFWC) column with a lightweight southern pine wood core confined by outer FRP sheets was manufactured using an improved pultrusion process. Axial compression tests with both ends pinned as boundary conditions were employed to investigate [...] Read more.
An innovative pultruded fiber reinforced polymer (FRP)–wood composite (PFWC) column with a lightweight southern pine wood core confined by outer FRP sheets was manufactured using an improved pultrusion process. Axial compression tests with both ends pinned as boundary conditions were employed to investigate the mechanical performance of such PFWC columns under concentric load. Through experimental investigations, the effects of the slenderness ratio on the failure modes and the axial load bearing capacities of the PFWC columns were evaluated. The failure modes showed that the specimens with a slenderness ratio less than 43.2 failed through compressive failure at junctions on FRP sheets, while those with slenderness ratios larger than 57.6 showed global buckling. Strain responses on specimens with different slenderness ratios are consistent with the observed failure modes. Finite element analysis was carried out to validate the experimental results, and satisfactory agreement was found between the failure modes and load–displacement curves. An empirical equation was developed with a new factor taking 0.65 into account to predict the load bearing capacities of the PFWC columns, and good agreement was found. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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14 pages, 8465 KiB  
Article
Natural Fibre-Reinforced Polymer Composites (NFRP) Fabricated from Lignocellulosic Fibres for Future Sustainable Architectural Applications, Case Studies: Segmented-Shell Construction, Acoustic Panels, and Furniture
by Hanaa Dahy
Sensors 2019, 19(3), 738; https://doi.org/10.3390/s19030738 - 12 Feb 2019
Cited by 55 | Viewed by 11328
Abstract
Due to the high amounts of waste generated from the building industry field, it has become essential to search for renewable building materials to be applied in wider and more innovative methods in architecture. One of the materials with the highest potential in [...] Read more.
Due to the high amounts of waste generated from the building industry field, it has become essential to search for renewable building materials to be applied in wider and more innovative methods in architecture. One of the materials with the highest potential in this area is natural fibre-reinforced polymers (NFRP), which are also called biocomposites, and are filled or reinforced with annually renewable lignocellulosic fibres. This would permit variable closed material cycles’ scenarios and should decrease the amounts of waste generated in the building industry. Throughout this paper, this discussion will be illustrated through a number of developments and 1:1 mockups fabricated from newly developed lignocellulosic-based biocomposites from both bio-based and non-bio-based thermoplastic and thermoset polymers. Recyclability, closed materials cycles, and design variations with diverse digital fabrication technologies will be discussed in each case. The mock-ups’ concepts, materials’ compositions, and fabrication methods are illustrated. In the first case study, a structural segmented shell construction is developed and constructed. In the second case study, acoustic panels were developed. The final case studies are two types of furniture, where each is developed from a different lignocellulosic-based biocomposite. All of the presented case studies show diverse architectural design possibilities, structural abilities, and physical building characteristics. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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20 pages, 5198 KiB  
Article
Performance Improvement of a Fiber-Reinforced Polymer Bar for a Reinforced Sea Sand and Seawater Concrete Beam in the Serviceability Limit State
by Jiafei Jiang, Jie Luo, Jiangtao Yu and Zhichen Wang
Sensors 2019, 19(3), 654; https://doi.org/10.3390/s19030654 - 05 Feb 2019
Cited by 31 | Viewed by 4504
Abstract
Fiber-reinforced polymer (FRP) has supreme resistance to corrosion and can be designed with optic fibers. FRP can be an alternative to steel reinforcement for concrete structures, and can serve as a sensor for smart concrete structures. Due to poor cracking control and bond [...] Read more.
Fiber-reinforced polymer (FRP) has supreme resistance to corrosion and can be designed with optic fibers. FRP can be an alternative to steel reinforcement for concrete structures, and can serve as a sensor for smart concrete structures. Due to poor cracking control and bond performance, the limit of flexural capacity in the serviceability limit state has not been determined, which has obstructed the wider application of FRP bars in smart structures. In this study, in order to overcome these shortcomings, a new engineering cementitious composite (ECC) with superior tensile strain capacity was used to replace the cover around the FRP bars in the tensile zone. To investigate the anti-cracking performance of the new composite beam, seven simply supported beams were designed. In the preliminary investigation, the longitudinal FRP bars in these beams were designed without optic fibers to focus on the mechanical behavior. The beams were tested under four-point load and measured using the digital sensor technique, digital image correlation (DIC). The test results showed that introducing a new ECC layer on the tensile side improves the cracking control and flexural behavior (load capacity and deformability) of a FRP-reinforced sea sand and seawater concrete (SSC) beam, especially in the serviceability limit state. We demonstrate the new composite beam can steadily and fully improve the tensile capacity of FRP bars, which is the basis of using FRP bars as sensors. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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14 pages, 3255 KiB  
Article
Experimental Investigation on Interfacial Defect Criticality of FRP-Confined Concrete Columns
by Renyuan Qin, Denvid Lau, Lik-ho Tam, Tiejun Liu, Dujian Zou and Ao Zhou
Sensors 2019, 19(3), 468; https://doi.org/10.3390/s19030468 - 24 Jan 2019
Cited by 24 | Viewed by 4700
Abstract
Defects between fiber reinforced polymer (FRP) and repaired concrete components may easily come out due to misoperation during manufacturing, environmental deterioration, or impact from external load during service life. The defects may cause a degraded structure performance and even the unexpected structural failure. [...] Read more.
Defects between fiber reinforced polymer (FRP) and repaired concrete components may easily come out due to misoperation during manufacturing, environmental deterioration, or impact from external load during service life. The defects may cause a degraded structure performance and even the unexpected structural failure. Different non-destructive techniques (NDTs) and sensors have been developed to assess the defects in FRP bonded system. The information of linking up the detected defects by NDTs and repair schemes is needed by assessing the criticality of detected defects. In this study, FRP confined concrete columns with interfacial defects were experimentally tested to determine the interfacial defect criticality on structural performance. It is found that interfacial defect can reduce the FRP confinement effectiveness, and ultimate strength and its corresponding strain of column deteriorate significantly if the interfacial defect area is larger than 50% of total confinement area. Meanwhile, proposed analytical model considering the defect ratio is validated for the prediction of stress–strain behavior of FRP confined columns. The evaluation of defect criticality could be made by comparing predicted stress–strain behavior with the original design to determine corresponding maintenance strategies. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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12 pages, 3303 KiB  
Article
Behaviour of Hybrid Steel and FRP-Reinforced Concrete—ECC Composite Columns under Reversed Cyclic Loading
by Fang Yuan, Liping Chen, Mengcheng Chen and Kaicheng Xu
Sensors 2018, 18(12), 4231; https://doi.org/10.3390/s18124231 - 02 Dec 2018
Cited by 11 | Viewed by 4078
Abstract
Fibre-reinforced polymer (FRP) is used widely in concrete structures owing to its noncorrosive, light-weight, nonmagnetic, and high tensile-strength properties. However, the FRP-reinforced concrete flexural member exhibits low ductility owing to the linear–elastic property of FRP reinforcement. Hybrid steel—FRP-reinforced concrete members exhibit good strength [...] Read more.
Fibre-reinforced polymer (FRP) is used widely in concrete structures owing to its noncorrosive, light-weight, nonmagnetic, and high tensile-strength properties. However, the FRP-reinforced concrete flexural member exhibits low ductility owing to the linear–elastic property of FRP reinforcement. Hybrid steel—FRP-reinforced concrete members exhibit good strength and ductility under flexure owing to the inelastic deformation of steel reinforcement. The existing investigations have focused on the mechanical behaviours of the hybrid steel—FRP-reinforced flexural members. Only few studies have been reported on the members under combined flexural and compression loads, such as columns, owing to the poor compressive behaviour of FRP bars. We herein propose a new type of hybrid steel—FRP-reinforced concrete—engineered cementitious composite (ECC) composite column with ECC applied to the plastic hinge region and tested it under reversed cyclic loading. The hybrid steel—FRP-reinforced concrete column was also tested for comparison. The influence of matrix type in the plastic hinge region on the failure mode, crack pattern, ultimate strength, ductility, and energy dissipation capacity, of the columns were evaluated systematically. We found that the substitution of concrete with ECC in the plastic hinge zone can prevent the local buckling of FRP bars efficiently, and subsequently improve the strength and ductility of the column substantially. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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27 pages, 5777 KiB  
Article
Confined Concrete in Fiber-Reinforced Polymer Partially Wrapped Square Columns: Axial Compressive Behavior and Strain Distributions by a Particle Image Velocimetry Sensing Technique
by Yong-Chang Guo, Shu-Hua Xiao, Jun-Wei Luo, Yu-Yi Ye and Jun-Jie Zeng
Sensors 2018, 18(12), 4118; https://doi.org/10.3390/s18124118 - 23 Nov 2018
Cited by 45 | Viewed by 3445
Abstract
Strengthening existing reinforced concrete (RC) columns using a partial wrapping strengthening technique (PWST) by fiber-reinforced polymer (FRP) strips has been widely implemented. However, compared with the confinement mechanism of confined concrete in columns strengthened with the FRP full wrapping strengthening technique (FWST), the [...] Read more.
Strengthening existing reinforced concrete (RC) columns using a partial wrapping strengthening technique (PWST) by fiber-reinforced polymer (FRP) strips has been widely implemented. However, compared with the confinement mechanism of confined concrete in columns strengthened with the FRP full wrapping strengthening technique (FWST), the confinement mechanism of confined concrete in FRP partially wrapped columns is less understood. This paper presents the results of an experimental investigation into the behavior of confined concrete in FRP partially wrapped square columns under axial compression. The effects of FRP strip width and thickness on stress–strain behavior were thoroughly investigated. The novel particle image velocimetry (PIV) non-contact strain sensing technique was adopted to measure the strain in the specimens. Results show that the axial strains as well as the hoop strains are generally larger at the mid-plane of adjacent FRP strips than those at the mid-plane of each FRP strip, and considerable variation in hoop strains along the height of the specimens was observed. Comparisons between the experimental results and predictions by existing design-oriented stress–strain models were carried out to examine the accuracy of the models. A new design-oriented stress–strain model is proposed for confined concrete in FRP partially wrapped square columns and the comparisons between laboratory results and predictions from the proposed model show that the proposed model is superior to the existing models. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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18 pages, 4720 KiB  
Article
Effects of Aggregate Types on the Stress-Strain Behavior of Fiber Reinforced Polymer (FRP)-Confined Lightweight Concrete
by Pengda Li, Lili Sui, Feng Xing, Xiaoxu Huang, Yingwu Zhou and Yanchun Yun
Sensors 2018, 18(10), 3525; https://doi.org/10.3390/s18103525 - 18 Oct 2018
Cited by 24 | Viewed by 3572
Abstract
The realization of reducing concrete self-weight is mainly to replace ordinary aggregates with lightweight aggregates; such replacement usually comes with some intrinsic disadvantages in concrete, such as high brittleness and lower mechanical properties. However, these shortages can be effectively remedied by external confinement [...] Read more.
The realization of reducing concrete self-weight is mainly to replace ordinary aggregates with lightweight aggregates; such replacement usually comes with some intrinsic disadvantages in concrete, such as high brittleness and lower mechanical properties. However, these shortages can be effectively remedied by external confinement such as fiber reinforced polymer (FRP) jacketing. To accurately predict the stress-strain behavior of lightweight concrete with lateral confinement, it is necessary to properly understand the coupling effects that are caused by diverse aggregates types and confinement level. In this study, FRP-confined lightweight concrete cylinder with varying aggregate types were tested under axial compression. Strain gauges and linear variable displacement transducers were used for monitoring the lateral and axial deformation of specimens during the tests. By sensing the strain and deformation data for the specimens under the tri-axial loads, the results showed that the lateral to axial strain relation is highly related to the aggregate types and confinement level. In addition, when compared with FRP-confined normal weight aggregate concrete, the efficiency of FRP confinement for lightweight concrete is gradually reduced with the increase of external pressure. Replace ordinary fine aggregate by its lightweight counterparts can be significantly improved the deformation capacity of FRP-confined lightweight concrete, meanwhile does not lead to the reduction of compressive strength. Plus, this paper modified a well-established stress-strain model for an FRP-confined lightweight concrete column, involving the effect of aggregate types. More accurate expressions pertaining to the deformation capacity and the stress-strain relation were proposed with reasonable accuracy. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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16 pages, 4584 KiB  
Article
Degradation of the In-plane Shear Modulus of Structural BFRP Laminates Due to High Temperature
by Yu-Jia Hu, Cheng Jiang, Wei Liu, Qian-Qian Yu and Yun-Lai Zhou
Sensors 2018, 18(10), 3361; https://doi.org/10.3390/s18103361 - 08 Oct 2018
Cited by 28 | Viewed by 3663
Abstract
The behavior of fiber reinforced polymer (FRP) composites at high temperature is a critical issue that needs to be clearly understood for their structural uses in civil engineering. However, due to technical difficulties during testing at high temperature, limited experimental investigations have been [...] Read more.
The behavior of fiber reinforced polymer (FRP) composites at high temperature is a critical issue that needs to be clearly understood for their structural uses in civil engineering. However, due to technical difficulties during testing at high temperature, limited experimental investigations have been conducted regarding the thermal behavior of basalt fiber reinforced polymer (BFRP) composites, especially for the in-plane shear modulus of BFRP laminates. To this end, both an analytical derivation and an experimental program were carried out in this work to study the in-plane shear modulus of BFRP laminates. After the analytical derivation, the in-plane shear modulus was investigated as a function of the elastic modulus in different directions (0°, 45° and 90° of the load-to-fiber angle) and Poisson’s ratio in the fiber direction. To obtain the in-plane shear modulus, the four parameters were tested at different temperatures from 20 to 250 °C. A novel non-contacting digital image correlation (DIC) sensing system was adopted in the high-temperature tests to measure the local strain field on the FRP samples. Based on the test results, it was found that the elastic moduli in different directions were reduced to a very low level (less than 20%) from 20 to 250 °C. Furthermore, the in-plane shear modulus of BFRP at 250 °C was only 3% of that at 20 °C. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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13 pages, 888 KiB  
Article
Pulse Ultrasonic Cure Monitoring of the Pultrusion Process
by Patrick Scholle and Michael Sinapius
Sensors 2018, 18(10), 3332; https://doi.org/10.3390/s18103332 - 05 Oct 2018
Cited by 5 | Viewed by 3090
Abstract
This article discusses the results of a series of experiments on pulse ultrasonic cure monitoring of carbon fiber reinforced plastics applied to the pultrusion process. The aim of this study is to validate the hypothesis that pulse ultrasonic cure monitoring can be applied [...] Read more.
This article discusses the results of a series of experiments on pulse ultrasonic cure monitoring of carbon fiber reinforced plastics applied to the pultrusion process. The aim of this study is to validate the hypothesis that pulse ultrasonic cure monitoring can be applied (a) for profiles having small cross sections such as 7 mm × 0.5 m m and (b) within the environment of the pultrusion process. Ultrasonic transducers are adhesively bonded to the pultrusion tool as actuators and sensors. The time-of-flight and the amplitude of an ultrasonic wave are analyzed to deduce the current curing state of the epoxy matrix. The experimental results show that ultrasonic cure monitoring is indeed applicable even to very thin cross sections. However, significant challenges can be reported when the techniques are used during the pultrusion process. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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14 pages, 3905 KiB  
Article
Fatigue Performance of RC Beams Strengthened with CFRP under Overloads with a Ladder Spectrum
by Zhan-Biao Chen, Pei-Yan Huang, Zheng-Wei Li, Xin-Yan Guo, Chen Zhao, Xiao-Hong Zheng and Yi Yang
Sensors 2018, 18(10), 3321; https://doi.org/10.3390/s18103321 - 03 Oct 2018
Cited by 7 | Viewed by 2909
Abstract
Vehicle overload is detrimental to bridges and traffic safety. This paper presents a study on the fatigue performance of typical reinforced concrete (RC) beams of highway bridges under vehicle overload. A definition method of vehicle overload and a construction method of overload ladder [...] Read more.
Vehicle overload is detrimental to bridges and traffic safety. This paper presents a study on the fatigue performance of typical reinforced concrete (RC) beams of highway bridges under vehicle overload. A definition method of vehicle overload and a construction method of overload ladder spectrum were first proposed based on traffic data acquisition, statistical analysis and structural calculation of the highway bridges in Guangzhou. A fatigue experimental method was also proposed with the three-ladder vehicle overload spectrum, and the fatigue tests of 15 RC beams strengthened with carbon fiber reinforced polymer (CFRP) under three loading levels were then carried out. The fatigue performance and the failure mechanism of the strengthened beams were presented and discussed, and two fatigue life prediction methods were proposed with the established modified Palmgren-Miner rule and the loading level equivalent method respectively. The results showed that the fatigue performance of the strengthened RC beams was severely degraded under overload ladder spectrum compared with that under constant amplitude cyclic load, and the life prediction methods were proved effective. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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14 pages, 3799 KiB  
Article
Numerical Sensing of Plastic Hinge Regions in Concrete Beams with Hybrid (FRP and Steel) Bars
by Fang Yuan and Mengcheng Chen
Sensors 2018, 18(10), 3255; https://doi.org/10.3390/s18103255 - 27 Sep 2018
Cited by 11 | Viewed by 3056
Abstract
Fibre-reinforced polymer (FRP)-reinforced concrete members exhibit low ductility due to the linear-elastic behaviour of FRP materials. Concrete members reinforced by hybrid FRP–steel bars can improve strength and ductility simultaneously. In this study, the plastic hinge problem of hybrid FRP–steel reinforced concrete beams was [...] Read more.
Fibre-reinforced polymer (FRP)-reinforced concrete members exhibit low ductility due to the linear-elastic behaviour of FRP materials. Concrete members reinforced by hybrid FRP–steel bars can improve strength and ductility simultaneously. In this study, the plastic hinge problem of hybrid FRP–steel reinforced concrete beams was numerically assessed through finite element analysis (FEA). Firstly, a finite element model was proposed to validate the numerical method by comparing the simulation results with the test results. Then, three plastic hinge regions—the rebar yielding zone, concrete crushing zone, and curvature localisation zone—of the hybrid reinforced concrete beams were analysed in detail. Finally, the effects of the main parameters, including the beam aspect ratio, concrete grade, steel yield strength, steel reinforcement ratio, steel hardening modulus, and FRP elastic modulus on the lengths of the three plastic zones, were systematically evaluated through parametric studies. It is determined that the hybrid reinforcement ratio exerts a significant effect on the plastic hinge lengths. The larger the hybrid reinforcement ratio, the larger is the extent of the rebar yielding zone and curvature localisation zone. It is also determined that the beam aspect ratio, concrete compressive strength, and steel hardening ratio exert significant positive effects on the length of the rebar yielding zone. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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15 pages, 5574 KiB  
Article
AFRP Influence on Parallel Bamboo Strand Lumber Beams
by Huizhong Zhang, Haitao Li, Ileana Corbi, Ottavia Corbi, Gang Wu, Chengjie Zhao and Tongwei Cao
Sensors 2018, 18(9), 2854; https://doi.org/10.3390/s18092854 - 29 Aug 2018
Cited by 31 | Viewed by 3713
Abstract
The mechanical properties of parallel bamboo strand lumber beams could be improved by aramid fiber reinforced polymer (AFRP). So far, no investigation has been conducted on the strengthening of engineering bamboo beams using AFRP. In order to study the efficiency of AFRP reinforcement [...] Read more.
The mechanical properties of parallel bamboo strand lumber beams could be improved by aramid fiber reinforced polymer (AFRP). So far, no investigation has been conducted on the strengthening of engineering bamboo beams using AFRP. In order to study the efficiency of AFRP reinforcement on parallel bamboo strand lumber beams, 13 beams had been tested and analyzed. Strain gauges and Laser Displacement Sensors were used for the tests. By sensing the strain and deformation data for the specimens under the applied loads, the results showed that AFRP can effectively improve the flexural mechanical properties of parallel bamboo strand lumber beams. However, this reinforcement cannot increase the deflection of bamboo beams indefinitely. When the cloth ratio was 0.48, the deflection of the specimens reached its maximum. With the increase of cloth ratio, the stiffness of parallel bamboo strand lumber beams was increasing. When the cloth ratio reached 0.72%, compared with the un-reinforced specimen, the stiffness increased by 15%. Therefore, it can be inferred that bonding AFRP on the considered specimens can increase the stiffness of parallel bamboo strand lumber beams. The ductility of the specimen can be effectively enhanced by adopting the AFRP provision. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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14 pages, 3561 KiB  
Article
Application of FRP Bolts in Monitoring the Internal Force of the Rocks Surrounding a Mine-Shield Tunnel
by Zhen Liu, Cuiying Zhou, Yiqi Lu, Xu Yang, Yanhao Liang and Lihai Zhang
Sensors 2018, 18(9), 2763; https://doi.org/10.3390/s18092763 - 22 Aug 2018
Cited by 9 | Viewed by 3450
Abstract
Monitoring the internal force of the rocks surrounding a mine-shield tunnel for the initial support of a mine-shield tunnel, in complex geological and hydrological environments, requires bolts with specific features such as high tensile strength, low shear strength, good insulation and resistance to [...] Read more.
Monitoring the internal force of the rocks surrounding a mine-shield tunnel for the initial support of a mine-shield tunnel, in complex geological and hydrological environments, requires bolts with specific features such as high tensile strength, low shear strength, good insulation and resistance to corrosion. As such, internal force monitoring has become an important issue in safety monitoring for such tunneling projects. In this paper, the adaptability of a mine-shield tunnel project in a corrosive environment is investigated. A fiberglass reinforced plastic (FRP) bolt with high tensile strength, low shear strength, resistance to fatigue, non-conductivity and resistance to corrosion is used as a probe in tandem with an anchor-head dynamometer to monitor the internal force of the rocks surrounding a mine-shield tunnel for initial support. Additionally, solar energy collection technology is introduced to create a remote monitoring system. Using a 2.5 km long railway tunnel located in the northeast of the Pearl River Delta of China as a case study, the present study shows that, compared with a conventional steel bolt, the FRP bolt has advantages, such as avoidance of the risks associated with the shield machine, insulation and resistance to corrosion. As a probe, the response of the FRP bolt to events such as a blasting vibration and a construction disturbance that results in internal changes in the surrounding rock demonstrates a clear pattern that is appropriate for monitoring the internal force of the rocks surrounding a mine-shield tunnel in a corrosive environment. FRP bolt-based monitoring not only provides new technological support for controlling the risk involved in the initial support of a mine-shield tunnel but can also be widely deployed in projects with special requirements for disassembly, conductivity and corrosion. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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19 pages, 3169 KiB  
Article
Theoretical and Numerical Study on Stress Intensity Factors for FRP-Strengthened Steel Plates with Double-Edged Cracks
by Hai-Tao Wang, Gang Wu and Yu-Yang Pang
Sensors 2018, 18(7), 2356; https://doi.org/10.3390/s18072356 - 20 Jul 2018
Cited by 31 | Viewed by 5603
Abstract
This paper presents a theoretical and numerical study on the stress intensity factors for double-edged cracked steel plates strengthened with fiber reinforced polymer (FRP) plates. Based on the stress intensity factor solution for infinite center-cracked steel plates strengthened with FRP plates, expressions of [...] Read more.
This paper presents a theoretical and numerical study on the stress intensity factors for double-edged cracked steel plates strengthened with fiber reinforced polymer (FRP) plates. Based on the stress intensity factor solution for infinite center-cracked steel plates strengthened with FRP plates, expressions of the stress intensity factors were proposed for double-edged cracked steel plates strengthened with FRP plates by introducing two correction factors: β and f. A finite element (FE) simulation was carried out to calculate the stress intensity factors of the steel plate specimens. Numerous combinations of the specimen width, crack length, FRP thickness and Young’s modulus, adhesive thickness, and shear modulus were considered to conduct the parametric investigation. The FE results were used to investigate the main influencing factors of the stress intensity factors and the correction factor, β. The expression of the correction factor, β, was formulated and calibrated based on the FE results. The proposed expressions of the stress intensity factors were a function of the applied stress, the crack length, the ratio between the crack length and the width of the steel plate, the stiffness ratio between the FRP plate and steel plate, the adhesive thickness, and the shear modulus. Finally, the theoretical results and numerical results were compared to validate the proposed expressions. Full article
(This article belongs to the Special Issue Advances in FRP Composites: Applications, Sensing, and Monitoring)
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