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21 pages, 6513 KiB

Open AccessArticle

Bond Performance of CFRP Strands to Grouting Admixture for Prestressed Structure and Development of Their Bond–Slip Constitutive Models

by Ce Wang, Shuai Guan, Md Sabbrojjaman and T. Tafsirojjaman

Polymers 2023, 15(13), 2906; https://doi.org/10.3390/polym15132906 - 30 Jun 2023

Cited by 1 | Viewed by 1386

Abstract

Prestressed concrete structures have witnessed widespread use in building and infrastructure applications during the last two decades due to their high stiffness and strength indices. However, structural failures caused by the corrosion of steel reinforcing bars or strands have proliferated, opening the door [...] Read more.

Prestressed concrete structures have witnessed widespread use in building and infrastructure applications during the last two decades due to their high stiffness and strength indices. However, structural failures caused by the corrosion of steel reinforcing bars or strands have proliferated, opening the door for carbon fibre-reinforced polymer (CFRP) strands as an excellent alternative with high corrosion resistance. The bonding interaction between the CFRP strands and concrete is the fundamental parameter in shaping the structural behaviour of CFRP prestressed concrete structures. In this paper, the bonding behaviour between CFRP strands and concrete with grouting admixture is experimentally investigated based on three groups of standard pull-out tests. The bond strength of CFRP strands was systematically studied and compared against steel strands. The untreated CFRP strands exhibited an inefficient bonding strength with the grouting admixture, equivalent to only 5% compared to steel strands of the same diameter. Surface coating with epoxy quartz sand can significantly improve the anchoring efficiency of CFRP strands up to 14 times compared to the untreated strands, which is approximately as efficient as steel strands. Moreover, the bond–slip curves between CFRP strands and concrete were analysed and were found to be different compared to steel strands. Finally, this study proposed bond–slip constitutive models of CFRP strands with better applicability, using an exponentially damped sine function to fit the residual segment of the curve. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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18 pages, 14057 KiB

Open AccessArticle

Experimental Study and Discrete Analysis of Compressive Properties of Glass Fiber-Reinforced Polymer (GFRP) Bars

by Zhilin Zhou, Long Meng, Feng Zeng, Shuai Guan, Jiahui Sun and T. Tafsirojjaman

Polymers 2023, 15(12), 2651; https://doi.org/10.3390/polym15122651 - 12 Jun 2023

Cited by 2 | Viewed by 2579

Abstract

Glass fiber-reinforced polymer (GFRP) has superior characteristics over traditional steel, such as lightweight, high strength, corrosion resistance and high durability. GFRP bars can be a useful alternative to steel bars in structures, specifically those in highly corrosive environments, as well as structures subjected [...] Read more.

Glass fiber-reinforced polymer (GFRP) has superior characteristics over traditional steel, such as lightweight, high strength, corrosion resistance and high durability. GFRP bars can be a useful alternative to steel bars in structures, specifically those in highly corrosive environments, as well as structures subjected to high compressive pressure such as bridge foundations. Digital image correlation (DIC) technology is used to analyze the strain evolution of GFRP bars under compression. It can be seen from using DIC technology that the surface strain of GFRP reinforcement is uniformly distributed and increases approximately linearly, and brittle splitting failure of GFRP bars happens due to locally occurring high strain at the failure stage. Moreover, there are limited studies on the use of distribution functions to describe the compressive strength and elastic modulus of GFRP. In this paper, Weibull distribution and gamma distribution are used to fit the compressive strength and compressive elastic modulus of GFRP bars. The average compressive strength is 667.05 MPa and follows Weibull distribution. Moreover, the average compressive elastic modulus is 47.51 GPa and follows gamma distribution. In order to verify that GFRP bars still have certain strength under compressive conditions, this paper provides a parameter reference for their large-scale application. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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23 pages, 2183 KiB

Open AccessArticle

Assessment of fib Bulletin 90 Design Provisions for Intermediate Crack Debonding in Flexural Concrete Elements Strengthened with Externally Bonded FRP

by Alba Codina, Cristina Barris, Younes Jahani, Marta Baena and Lluís Torres

Polymers 2023, 15(3), 769; https://doi.org/10.3390/polym15030769 - 2 Feb 2023

Cited by 2 | Viewed by 2593

Abstract

With the assessment of intermediate crack debonding (ICD) being a subject of main importance in the design of reinforced concrete (RC) beams strengthened in flexure with externally bonded fibre-reinforced polymer (FRP), several approaches to predict the debonding loads have been developed in recent [...] Read more.

With the assessment of intermediate crack debonding (ICD) being a subject of main importance in the design of reinforced concrete (RC) beams strengthened in flexure with externally bonded fibre-reinforced polymer (FRP), several approaches to predict the debonding loads have been developed in recent decades considering different models and strategies. This study presents an analysis of formulations with different levels of approximation collected in the fib Bulletin 90 regarding this failure mode, comparing the theoretical predictions with experimental results. The carried-out experiments consisted of three RC beams strengthened with carbon FRP (CFRP) tested under a four-point bending configuration with different concrete strengths and internal steel reinforcement ratios. With failure after steel yielding, higher concrete strength, as well as a higher reinforcement ratio, lead to a higher bending capacity. In addition, the performance of the models is assessed through the experimental-to-predicted failure load ratios from an experimental database of 65 RC beams strengthened with CFRP gathered from the literature. The results of the comparative study show that the intermediate crack debonding failure mode is well predicted by all models with a mean experimental-to-predicted failure load ratio between 0.96 and 1.10 in beams tested under three- or four-point bending configurations. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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12 pages, 3791 KiB

Open AccessArticle

Effect of Hydrothermal Environment on Mechanical Properties and Electrical Response Behavior of Continuous Carbon Fiber/Epoxy Composite Plates

by Runtian Zhu, Xiaolu Li, Cankun Wu, Longji Du, Xusheng Du and T. Tafsirojjaman

Polymers 2022, 14(19), 4072; https://doi.org/10.3390/polym14194072 - 28 Sep 2022

Cited by 2 | Viewed by 1653

Abstract

In this work, the effect of a hydrothermal environment on mechanical properties and the electrical response behavior of continuous carbon fiber/epoxy (CFRE) composite produced by the pultrusion method were investigated. Due to the relatively uniform distribution of fibers and lack of resin-rich interlayer [...] Read more.

In this work, the effect of a hydrothermal environment on mechanical properties and the electrical response behavior of continuous carbon fiber/epoxy (CFRE) composite produced by the pultrusion method were investigated. Due to the relatively uniform distribution of fibers and lack of resin-rich interlayer area, this effect for the pultruded CFRE composite plates is different from the common CFRE laminated composites. Firstly, its hygroscopicity behavior was studied. The absorption ratio increases rapidly to 1.02% within 3 days before reaching a relatively stable state. A three-point bending test, a Vickers hardness test, a thermogravimetric analysis (TGA), and a scanning electron microscope (SEM) analysis were performed to investigate the effect of the hydrothermal environment on the mechanical properties and thermal stability of the CFRE composite. The results indicated that the bending strength decreased quickly within 3 days of hydrothermal treatment, followed by a stable trend, which coincided with that of the hygroscopicity behavior of the composites. The fracture surface analysis indicated that the interfacial properties of carbon fibers in the epoxy matrix were decreased after the hydrothermal treatment, and more carbon fibers could be pulled out from the CFRE in the hygroscopic state. After the hydrothermal treatment, the micro-hardness of the composites was reduced by 25%. TGA confirmed the decreased thermal stability of the CFRE composites after the hydrothermal treatment as well. Moreover, the hydrothermally treated CFRE composites could a reach stable resistance response more readily. The revealing of the effect of moisture and hot environment on the mechanical properties and electrical response behavior of pultruded CFRE composites prepares the ground for their design and practical application in the corresponding environment. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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19 pages, 12925 KiB

Open AccessArticle

Experimental Research on Bonded Anchorage of Carbon Fiber Reinforced Polymer Prestressed Strands

by Liqiang Jia, Bo Wang and T. Tafsirojjaman

Polymers 2022, 14(19), 4015; https://doi.org/10.3390/polym14194015 - 25 Sep 2022

Cited by 5 | Viewed by 2270

Abstract

Aiming at the problems of a large number of corrosion and fatigue damage of the current prestressed steel strands, this paper adopts carbon fiber-reinforced composite (CFRP) strand with better corrosion resistance and fatigue resistance and uses it in concrete structures. The bond anchorage [...] Read more.

Aiming at the problems of a large number of corrosion and fatigue damage of the current prestressed steel strands, this paper adopts carbon fiber-reinforced composite (CFRP) strand with better corrosion resistance and fatigue resistance and uses it in concrete structures. The bond anchorage is usually used to anchor CFRP tension members, which bonds the CFRP through the binding medium. Through experimental research on the CFRP strand bond anchorage, the inner taper of the CFRP prestressed strand cone was anchored and the influence of different anchor lengths and bonding media on the anchorage performance was determined. The test results demonstrate that the taper of the conical anchorage described in this paper is a key factor affecting its anchorage performance and increasing the inner taper within a certain range is beneficial to improving the anchorage performance of the conical anchorage. The bonded anchorage of the CFRP prestressed strand with a 200 mm anchor is the most reliable and efficient, as the taper of the 200 mm anchor is the largest. The average anchoring efficiency coefficient of the 200 mm anchor was 96.4%, which is 3.7% and 2.6% higher than the average anchoring efficiency coefficient of 220 mm and 250 mm anchors, respectively. The anchoring efficiency of the anchor is also high (94.1%) when the epoxy resin mortar is used as the bonding medium. Moreover, after an appropriate amount of quartz sand is added to the epoxy resin, the overall comprehensive performance of the anchor can be improved to a certain extent and the stress of the CFRP strand can be improved. The coupling between ultra-high-performance concrete dry mix (UHPC-GJL) and CFRP strand materials is not suitable for UHPC-GJL being used, as its binding medium as the average anchoring efficiency coefficient is only 44.5% when UHPC-GJL is used as the anchor bonding medium. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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23 pages, 5953 KiB

Open AccessArticle

Hybrid Ensemble Model for Predicting the Strength of FRP Laminates Bonded to the Concrete

by Anas Abdulalem Alabdullh, Rahul Biswas, Jitendra Gudainiyan, Kaffayatullah Khan, Abdullah Hussain Bujbarah, Qasem Ahmed Alabdulwahab, Muhammad Nasir Amin and Mudassir Iqbal

Polymers 2022, 14(17), 3505; https://doi.org/10.3390/polym14173505 - 26 Aug 2022

Cited by 8 | Viewed by 1774

Abstract

The goal of this work was to use a hybrid ensemble machine learning approach to estimate the interfacial bond strength (IFB) of fibre-reinforced polymer laminates (FRPL) bonded to the concrete using the results of a single shear-lap test. A database comprising 136 data [...] Read more.

The goal of this work was to use a hybrid ensemble machine learning approach to estimate the interfacial bond strength (IFB) of fibre-reinforced polymer laminates (FRPL) bonded to the concrete using the results of a single shear-lap test. A database comprising 136 data was used to train and validate six standalone machine learning models, namely, artificial neural network (ANN), extreme machine learning (ELM), the group method of data handling (GMDH), multivariate adaptive regression splines (MARS), least square-support vector machine (LSSVM), and Gaussian process regression (GPR). The hybrid ensemble (HENS) model was subsequently built, employing the combined and trained predicted outputs of the ANN, ELM, GMDH, MARS, LSSVM, and GPR models. In comparison with the standalone models employed in the current investigation, it was observed that the suggested HENS model generated superior predicted accuracy with R² (training = 0.9783, testing = 0.9287), VAF (training = 97.83, testing = 92.87), RMSE (training = 0.0300, testing = 0.0613), and MAE (training = 0.0212, testing = 0.0443). Using the training and testing dataset to assess the predictive performance of all models for IFB prediction, it was discovered that the HENS model had the greatest predictive accuracy throughout both stages with an R² of 0.9663. According to the findings of the experiments, the newly developed HENS model has a great deal of promise to be a fresh approach to deal with the overfitting problems of CML models and thus may be utilised to forecast the IFB of FRPL. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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21 pages, 4385 KiB

Open AccessArticle

A Hybrid SVR-Based Prediction Model for the Interfacial Bond Strength of Externally Bonded FRP Laminates on Grooves with Concrete Prisms

by Kaffayatullah Khan, Mudassir Iqbal, Rahul Biswas, Muhammad Nasir Amin, Sajid Ali, Jitendra Gudainiyan, Anas Abdulalim Alabdullah and Abdullah Mohammad Abu Arab

Polymers 2022, 14(15), 3097; https://doi.org/10.3390/polym14153097 - 29 Jul 2022

Cited by 6 | Viewed by 2058

Abstract

The current work presents a comparative study of hybrid models that use support vector machines (SVMs) and meta-heuristic optimization algorithms (MOAs) to predict the ultimate interfacial bond strength (IBS) capacity of fiber-reinforced polymer (FRP). More precisely, a dataset containing 136 experimental tests was [...] Read more.

The current work presents a comparative study of hybrid models that use support vector machines (SVMs) and meta-heuristic optimization algorithms (MOAs) to predict the ultimate interfacial bond strength (IBS) capacity of fiber-reinforced polymer (FRP). More precisely, a dataset containing 136 experimental tests was first collected from the available literature for the development of hybrid SVM models. Five MOAs, namely the particle swarm optimization, the grey wolf optimizer, the equilibrium optimizer, the Harris hawks optimization and the slime mold algorithm, were used; five hybrid SVMs were constructed. The performance of the developed SVMs was then evaluated. The accuracy of the constructed hybrid models was found to be on the higher side, with R² ranges between 0.8870 and 0.9774 in the training phase and between 0.8270 and 0.9294 in the testing phase. Based on the experimental results, the developed SVM–HHO (a hybrid model that uses an SVM and the Harris hawks optimization) was overall the most accurate model, with R² values of 0.9241 and 0.9241 in the training and testing phases, respectively. Experimental results also demonstrate that the developed hybrid SVM can be used as an alternate tool for estimating the ultimate IBS capacity of FRP concrete in civil engineering projects. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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18 pages, 3437 KiB

Open AccessArticle

Investigating the Bond Strength of FRP Rebars in Concrete under High Temperature Using Gene-Expression Programming Model

by Muhammad Nasir Amin, Mudassir Iqbal, Fadi Althoey, Kaffayatullah Khan, Muhammad Iftikhar Faraz, Muhammad Ghulam Qadir, Anas Abdulalim Alabdullah and Ali Ajwad

Polymers 2022, 14(15), 2992; https://doi.org/10.3390/polym14152992 - 24 Jul 2022

Cited by 9 | Viewed by 2167

Abstract

In recent times, the use of fibre-reinforced plastic (FRP) has increased in reinforcing concrete structures. The bond strength of FRP rebars is one of the most significant parameters for characterising the overall efficacy of the concrete structures reinforced with FRP. However, in cases [...] Read more.

In recent times, the use of fibre-reinforced plastic (FRP) has increased in reinforcing concrete structures. The bond strength of FRP rebars is one of the most significant parameters for characterising the overall efficacy of the concrete structures reinforced with FRP. However, in cases of elevated temperature, the bond of FRP-reinforced concrete can deteriorate depending on a number of factors, including the type of FRP bars used, its diameter, surface form, anchorage length, concrete strength, and cover thickness. Hence, accurate quantification of FRP rebars in concrete is of paramount importance, especially at high temperatures. In this study, an artificial intelligence (AI)-based genetic-expression programming (GEP) method was used to predict the bond strength of FRP rebars in concrete at high temperatures. In order to predict the bond strength, we used failure mode temperature, fibre type, bar surface, bar diameter, anchorage length, compressive strength, and cover-to-diameter ratio as input parameters. The experimental dataset of 146 tests at various elevated temperatures were established for training and validating the model. A total of 70% of the data was used for training the model and remaining 30% was used for validation. Various statistical indices such as correlation coefficient (R), the mean absolute error (MAE), and the root-mean-square error (RMSE) were used to assess the predictive veracity of the GEP model. After the trials, the optimum hyperparameters were 150, 8, and 4 as number of chromosomes, head size and number of genes, respectively. Different genetic factors, such as the number of chromosomes, the size of the head, and the number of genes, were evaluated in eleven separate trials. The results as obtained from the rigorous statistical analysis and parametric study show that the developed GEP model is robust and can predict the bond strength of FRP rebars in concrete under high temperature with reasonable accuracy (i.e., R, RMSE and MAE 0.941, 2.087, and 1.620, and 0.935, 2.370, and 2.046, respectively, for training and validation). More importantly, based on the FRP properties, the model has been translated into traceable mathematical formulation for easy calculations. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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16 pages, 1353 KiB

Open AccessArticle

Estimating Flexural Strength of FRP Reinforced Beam Using Artificial Neural Network and Random Forest Prediction Models

by Kaffayatullah Khan, Mudassir Iqbal, Babatunde Abiodun Salami, Muhammad Nasir Amin, Izaz Ahamd, Anas Abdulalim Alabdullah, Abdullah Mohammad Abu Arab and Fazal E. Jalal

Polymers 2022, 14(11), 2270; https://doi.org/10.3390/polym14112270 - 2 Jun 2022

Cited by 20 | Viewed by 2921

Abstract

An accurate calculation of the flexural capacity of flexural members is vital for the safe and economical design of FRP reinforced structures. The existing empirical models are not accurately calculating the flexural capacity of beams and columns. This study investigated the estimation of [...] Read more.

An accurate calculation of the flexural capacity of flexural members is vital for the safe and economical design of FRP reinforced structures. The existing empirical models are not accurately calculating the flexural capacity of beams and columns. This study investigated the estimation of the flexural capacity of beams using non-linear capabilities of two Artificial Intelligence (AI) models, namely Artificial neural network (ANN) and Random Forest (RF) Regression. The models were trained using optimized hyperparameters obtained from the trial-and-error method. The coefficient of correlation (R), Mean Absolute Error, and Root Mean Square Error (RMSE) were observed as 0.99, 5.67 kN-m, and 7.37 kN-m, for ANN, while 0.97, 7.63 kN-m, and 8.02 kN-m for RF regression model, respectively. Both models showed close agreement between experimental and predicted results; however, the ANN model showed superior accuracy and flexural strength performance. The parametric and sensitivity analysis of the ANN models showed that an increase in bottom reinforcement, width and depth of the beam, and increase in compressive strength increased the bending moment capacity of the beam, which shows the predictions by the model are corroborated with the literature. The sensitivity analysis showed that variation in bottom flexural reinforcement is the most influential parameter in yielding flexural capacity, followed by the overall depth and width of the beam. The change in elastic modulus and ultimate strength of FRP manifested the least importance in contributing flexural capacity. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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23 pages, 5817 KiB

Open AccessArticle

Predicting Bond Strength between FRP Rebars and Concrete by Deploying Gene Expression Programming Model

by Muhammad Nasir Amin, Mudassir Iqbal, Babatunde Abiodun Salami, Arshad Jamal, Kaffayatullah Khan, Abdullah Mohammad Abu-Arab, Qasem Mohammed Sultan Al-Ahmad and Muhammad Imran

Polymers 2022, 14(11), 2145; https://doi.org/10.3390/polym14112145 - 25 May 2022

Cited by 6 | Viewed by 2548

Abstract

Rebars made of fiber-reinforced plastic (FRP) might be the future reinforcing material, replacing mild steel rebars, which are prone to corrosion. The bond characteristics of FRP rebars differ from those of mild steel rebars due to their different stress-strain behavior than mild steel. [...] Read more.

Rebars made of fiber-reinforced plastic (FRP) might be the future reinforcing material, replacing mild steel rebars, which are prone to corrosion. The bond characteristics of FRP rebars differ from those of mild steel rebars due to their different stress-strain behavior than mild steel. As a result, determining the bond strength (BS) qualities of FRP rebars is critical. In this work, BS data for FRP rebars was investigated, utilizing non-linear capabilities of gene expression programming (GEP) on 273 samples. The BS of FRP and concrete was considered a function of bar surface (Bs), bar diameter (d_b), concrete compressive strength (f_c′), concrete-cover-bar-diameter ratio (c/d), and embedment-length-bar-diameter ratio (l/d). The investigation of the variable number of genetic parameters such as number of chromosomes, head size, and number of genes was undertaken such that 11 different models (M1–M11) were created. The results of accuracy evaluation parameters, namely coefficient of determination (R²), mean absolute error (MAE), and root mean square error (RMSE) imply that the M11 model outperforms other created models for the training and testing stages, with values of (0.925, 0.751, 1.08) and (0.9285, 0.802, 1.11), respectively. The values of R² and error indices showed that there is very close agreement between the experimental and predicted results. 30 number chromosomes, 9 head size, and 5 genes yielded the optimum model. The parametric analysis revealed that d_b, c/d, and l/d significantly affected the BS. The FRP rebar diameter size is greater than 10 mm, whereas a l/d ratio of more than 12 showed a considerable decrease in BS. In contrast, the rise in c/d ratio revealed second-degree increasing trend of BS. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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23 pages, 10587 KiB

Open AccessArticle

An Experimental and Numerical Investigation into the Durability of Fibre/Polymer Composites with Synthetic and Natural Fibres

by Abdalrahman Alajmi, Rajab Abousnina, Abdullah Shalwan, Sultan Alajmi, Golnaz Alipour, Tafsirojjaman Tafsirojjaman and Geoffrey Will

Polymers 2022, 14(10), 2024; https://doi.org/10.3390/polym14102024 - 16 May 2022

Cited by 3 | Viewed by 3799

Abstract

Progress in engineering research has shifted the interest from traditional monolithic materials to modern materials such as fibre reinforced composites (FRC). This paradigm shift can be attributed to the unique mechanical characteristics of FRCs such as high strength to weight ratio, good flexural [...] Read more.

Progress in engineering research has shifted the interest from traditional monolithic materials to modern materials such as fibre reinforced composites (FRC). This paradigm shift can be attributed to the unique mechanical characteristics of FRCs such as high strength to weight ratio, good flexural strength, and fracture toughness. At present, synthetic composites dominate the automotive, aerospace, sporting, and construction industries despite serious drawbacks such as costly raw materials, high manufacturing costs, non-recyclability, toxicity, and non-biodegradability. To address these issues, naturally occurring plant fibres (such as jute, hemp, sisal) are being increasingly researched as potential reinforcements for biodegradable or non-biodegradable polymer matrices to produce environmentally friendly composites. In this study, sisal fibres were selected owing to their low production costs, sustainability, recyclability, and biodegradability. The hydrothermal ageing and mechanical characteristics of sisal fibre-reinforced epoxy (SFRE) composites were determined and compared with glass fibre-reinforced epoxy (GFRE) synthetic composites. Moreover, a first-of-its-kind numerical model have been developed to study the hydrothermal ageing and mechanical characteristics of SFRE, along with GFRE, using ANSYS software. Moreover, microstructural analysis of flexural tested GFRE and SFRE samples were carried out to identify the microstructural properties of the composites. Both experimental and numerical results exhibited an influence of short- or long-term hydrothermal treatment on the flexural properties of glass and sisal fibre-based composites. In the case of GFRE, the moisture uptake and fibre-matrix de-bonding existed, but it is less severe as compared to the SFRE composites. It was found that the dosage of sisal fibres largely determines the ultimate mechanical performance of the composite. Nonetheless, the experimental and numerical flexural strengths of SFRE were comparable to GFRE composites. This exhibited that the SFRE composites possess the potentiality as a sustainable material for advanced applications. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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18 pages, 3635 KiB

Open AccessArticle

GEP Tree-Based Prediction Model for Interfacial Bond Strength of Externally Bonded FRP Laminates on Grooves with Concrete Prism

by Muhammad Nasir Amin, Mudassir Iqbal, Arshad Jamal, Shahid Ullah, Kaffayatullah Khan, Abdullah M. Abu-Arab, Qasem M. S. Al-Ahmad and Sikandar Khan

Polymers 2022, 14(10), 2016; https://doi.org/10.3390/polym14102016 - 16 May 2022

Cited by 15 | Viewed by 2096

Abstract

Reinforced concrete structures are subjected to frequent maintenance and repairs due to steel reinforcement corrosion. Fiber-reinforced polymer (FRP) laminates are widely used for retrofitting beams, columns, joints, and slabs. This study investigated the non-linear capability of artificial intelligence (AI)-based gene expression programming (GEP) [...] Read more.

Reinforced concrete structures are subjected to frequent maintenance and repairs due to steel reinforcement corrosion. Fiber-reinforced polymer (FRP) laminates are widely used for retrofitting beams, columns, joints, and slabs. This study investigated the non-linear capability of artificial intelligence (AI)-based gene expression programming (GEP) modelling to develop a mathematical relationship for estimating the interfacial bond strength (IBS) of FRP laminates on a concrete prism with grooves. The model was based on five input parameters, namely axial stiffness (E_ft_f), width of FRP plate (b_f), concrete compressive strength (f_c′), width of groove (b_g), and depth of the groove (h_g), and IBS was considered the target variable. Ten trials were conducted based on varying genetic parameters, namely the number of chromosomes, head size, and number of genes. The performance of the models was evaluated using the correlation coefficient (R), mean absolute error (MAE), and root mean square error (RMSE). The genetic variation revealed that optimum performance was obtained for 30 chromosomes, 11 head sizes, and 4 genes. The values of R, MAE, and RMSE were observed as 0.967, 0.782 kN, and 1.049 kN for training and 0.961, 1.027 kN, and 1.354 kN. The developed model reflected close agreement between experimental and predicted results. This implies that the developed mathematical equation was reliable in estimating IBS based on the available properties of FRPs. The sensitivity and parametric analysis showed that the axial stiffness and width of FRP are the most influential parameters in contributing to IBS. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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17 pages, 3466 KiB

Open AccessArticle

Life-Cycle Cost Analysis of Long-Span CFRP Cable-Stayed Bridges

by Yue Liu, Mingyang Gu, Xiaogang Liu and T. Tafsirojjaman

Polymers 2022, 14(9), 1740; https://doi.org/10.3390/polym14091740 - 25 Apr 2022

Cited by 9 | Viewed by 2541

Abstract

With the advantages of high strength, light weight, high corrosion and fatigue resistance, and low relaxation, carbon-fiber-reinforced polymer (CFRP) is an excellent cable material for cable-stayed bridges. However, the relatively high unit price of CFRP compared to that of steel may hinder the [...] Read more.

With the advantages of high strength, light weight, high corrosion and fatigue resistance, and low relaxation, carbon-fiber-reinforced polymer (CFRP) is an excellent cable material for cable-stayed bridges. However, the relatively high unit price of CFRP compared to that of steel may hinder the large-scale application of CFRP stay cables. This paper presents the economic comparison between long-span cable-stayed bridges using CFRP cables and the corresponding steel cable-stayed bridges through life-cycle cost analysis (LCCA). Three CFRP cable-stayed bridges with a main span of 600 m, 1200 m, and 1800 m, respectively, along with their steel counterparts, were designed, and their life-cycle costs (LCCs) were calculated. The comparison of LCCs was not only between the CFRP and steel cable-stayed bridges with the same span, but also between the cable-stayed bridges with different spans. Furthermore, the different unit prices of CFRP cables and different replacement frequencies of steel cables were also investigated. The results show that the initial design and construction cost of the long-span CFRP cable-stayed bridge is higher than that of the corresponding steel cable-stayed bridge, although using CFRP cables can reduce the materials used, primarily due to the higher unit price of the CFRP cable. Despite the higher initial cost, the long-span CFRP cable-stayed bridge can still achieve lower LCC than the steel cable-stayed bridge, because it has significantly lower rehabilitation cost and user cost, as well as slightly lower vulnerability cost. Furthermore, with the increase in the main span and the decrease in the unit price of CFRP cables, the LCC advantage of the long-span CFRP cable-stayed bridge becomes more obvious. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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Review

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47 pages, 8183 KiB

Open AccessReview

Recent Trends in Advanced Radiation Shielding Concrete for Construction of Facilities: Materials and Properties

by Muhd Afiq Hizami Abdullah, Raizal Saifulnaz Muhammad Rashid, Mugahed Amran, Farzad Hejazii, N. M. Azreen, Roman Fediuk, Yen Lei Voo, Nikolai Ivanovich Vatin and Mohd Idzat Idris

Polymers 2022, 14(14), 2830; https://doi.org/10.3390/polym14142830 - 12 Jul 2022

Cited by 52 | Viewed by 12515

Abstract

Nuclear energy offers a wide range of applications, which include power generation, X-ray imaging, and non-destructive tests, in many economic sectors. However, such applications come with the risk of harmful radiation, thereby requiring shielding to prevent harmful effects on the surrounding environment and [...] Read more.

Nuclear energy offers a wide range of applications, which include power generation, X-ray imaging, and non-destructive tests, in many economic sectors. However, such applications come with the risk of harmful radiation, thereby requiring shielding to prevent harmful effects on the surrounding environment and users. Concrete has long been used as part of structures in nuclear power plants, X-ray imaging rooms, and radioactive storage. The direction of recent research is headed toward concrete’s ability in attenuating harmful energy radiated from nuclear sources through various alterations to its composition. Radiation shielding concrete (RSC) is a composite-based concrete that was developed in the last few years with heavy natural aggregates such as magnetite or barites. RSC is deemed a superior alternative to many types of traditional normal concrete in terms of shielding against the harmful radiation, and being economical and moldable. Given the merits of RSCs, this article presents a comprehensive review on the subject, considering the classifications, alternative materials, design additives, and type of heavy aggregates used. This literature review also provides critical reviews on RSC performance in terms of radiation shielding characteristics, mechanical strength, and durability. In addition, this work extensively reviews the trends of development research toward a broad understanding of the application possibilities of RSC as an advanced concrete product for producing a robust and green concrete composite for the construction of radiation shielding facilities as a better solution for protection from sources of radiation. Furthermore, this critical review provides a view of the progress made on RSCs and proposes avenues for future research on this hotspot research topic. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites in Construction Materials)

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Fiber-Reinforced Polymer Composites in Construction Materials

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