Journal articles on the topic 'FRP-confined concrete'
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Lim, Jian Chin, and Togay Ozbakkloglu. "Comparison of Stress-Strain Relationships of FRP and Actively Confined High-Strength Concrete: Experimental Observations." Advanced Materials Research 919-921 (April 2014): 29–34. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.29.
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It is well established that lateral confinement of concrete enhances its axial strength and deformability. It is often assumed that, at a same level of confining pressure, the axial compressive stress and strain of fiber reinforced polymer (FRP)-confined concrete at a given lateral strain are the same as those in concrete actively confined concrete. To assess the validity of this assumption, an experimental program relating both types of confinement systems was conducted. 25 FRP-confined and actively confined high-strength concrete (HSC) specimens cast from a same batch of concrete were tested under axial compression. The axial stress-strain and lateral strain-axial strain curves obtained from the two different confinement systems were assessed. The results indicate that, at a given axial strain, lateral strains of actively confined and FRP-confined concretes correspond, when they are subjected to the same lateral confining pressure. However, it is observed that, at these points of intersections on axial strain-lateral strain curves, FRP-confined concrete exhibits a lower axial stress than the actively confined concrete, indicating that the aforementioned assumption is not accurate. The test results indicate that the difference in the axial stresses of FRP-confined and actively confined HSC becomes more significant with an increase in the level of confining pressure.
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Spoelstra, Marijn R., and Giorgio Monti. "FRP-Confined Concrete Model." Journal of Composites for Construction 3, no. 3 (August 1999): 143–50. http://dx.doi.org/10.1061/(asce)1090-0268(1999)3:3(143).
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Mirmiran, Amir, Aashish Singhvi, and Giorgio Monti. "FRP-Confined Concrete Model." Journal of Composites for Construction 5, no. 1 (February 2001): 62–65. http://dx.doi.org/10.1061/(asce)1090-0268(2001)5:1(62).
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Yu, Feng, and Ping Wu. "Study on Stress-Strain Relationship of FRP-Confined Concrete Filled Steel Tubes." Advanced Materials Research 163-167 (December 2010): 3826–29. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.3826.
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FRP-confined concrete filled steel tube may fully use the character of FRP-confined concrete and concrete filled steel tube. Based on the analysis of existing experimental data, the formula of ultimate bearing capacity of FRP-confined concrete filled steel tube is proposed. The mechanical behavior of FRP-confined concrete filled steel tube is mainly related to the equivalent confinement effect coefficient before the rupture of FRP. Based on the static equilibrium condition, the equivalent conversion section is adopted; taking as main parameter, the simplified stress-strain model of FRP-confined concrete filled steel tube is established. The predictions of the model agree well with test data.
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Lim, Jian Chin. "Influence of Concrete Age on Compressive Behavior of FRP-Confined Concrete." Applied Mechanics and Materials 744-746 (March 2015): 162–68. http://dx.doi.org/10.4028/www.scientific.net/amm.744-746.162.
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This paper presents the results of an experimental study on the influence of concrete age on the compressive behavior of fiber reinforced polymer (FRP)-confined normal-strength (NSC) and high-strength concrete (HSC). The first part of the paper presents the results of 18 FRP-confined and 18 unconfined concrete specimens tested at 7 and 28 days. To extend the investigation with specimens with concrete ages up to 900 days, existing test results of FRP-confined concrete was assembled from the literature. Based on observations from both short-and long-term influences of concrete age on compressive behavior of FRP-confined concrete, a number of important findings were drawn and are presented in the second part of the paper. It was observed that, at a same level of FRP confinement and unconfined concrete strength, the stress-strain behavior of FRP-confined concrete changes with concrete age. This difference is particularly pronounced at the transition zone of the stress-strain curves. It is found that, in the short-term, the ultimate condition of FRP-confined concrete is not significantly affected by the age of concrete. However, in the long-term, slight decreases in the compressive strength and the ultimate axial strain are observed with an increase in concrete age.
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Qazi, Asad U., Qasim S. Khan, H. Abrar Ahmad, and Thong M. Pham. "Axial Behavior of FRP Confined Concrete Using Locally Available Low-Cost Wraps." Sustainability 14, no. 16 (August 12, 2022): 9989. http://dx.doi.org/10.3390/su14169989.
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This study investigates the influences of three types of locally available low-cost Fiber Reinforced Polymers (FRP) wraps and two concrete mix designs on the axial behavior of FRP confined concrete. The experimental program comprised four unconfined (control), four glass FRP Matt Strand (GFRP-MS) confined concrete, four glass FRP Rowing (GFRP-R) confined concrete and four carbon FRP (CFRP) confined concrete specimens with a diameter of 150 mm and a height of 300 mm tested under axial compression. The specimens were prepared using two normal strength concrete mix designs, i.e., Mix-A and Mix-B. The experimental results exhibited that an increase in the confined concrete strength per unit cost ratio of a single layer of GFRP-MS was about two times of a single layer of CFRP wrap, whereas the increase in confined concrete strength per unit cost ratio of single layer of GFRP-R was about four times of a single layer of CFRP wrap. GFRP-MS and GFRP-R wraps can exhibit similar confined strengths as CFRP wrap with six and twelve times lower costs, respectively, than CFRP wrap. Mix-B concrete specimens exhibited higher confined concrete strengths but lower confined concrete strain than Mix-A concrete specimens. A database of 140 FRP confined concrete specimens was developed based on a set of specific criteria to develop a design-oriented model to predict the FRP confined concrete strength. The predicted confined concrete strengths matched well with the experimental confined concrete strengths. The two layers of GFRP-R exhibited similar confined concrete strength as CFRP wrap. In addition, GFRP-R exhibited high cement strength index (CSI) and low embodied CO2 index (CI).
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Cao, Yugui, Muyu Liu, Yang Zhang, Jun Hu, and Shengchun Yang. "Effect of Strain Rates on the Stress–Strain Behavior of FRP-Confined Pre-Damaged Concrete." Materials 13, no. 5 (February 28, 2020): 1078. http://dx.doi.org/10.3390/ma13051078.
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There are many studies on fiber-reinforced polymer (FRP)-confined pre-damaged concrete under quasi-static strain rates. However, few studies have focused on FRP-confined pre-damaged concrete under high strain rates. Thus, an experimental and analytical investigation was conducted to obtain the mechanical behavior of FRP-confined pre-damaged concrete under different strain rates. The results show that the stress–strain curves, ultimate stress, and strain values were affected by strain rate and the extent of concrete damage. A stress–strain model of FRP-confined pre-damaged concrete considering the strain rate was developed by modifying a stress–strain model of FRP-confined pre-damaged concrete under quasi-static loading. The proposed model was evaluated by using test data. The evaluation results show that the proposed model can predict the stress–strain behavior of FRP-confined pre-damaged concrete under different strain rates.
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Jiang, Cheng, and Yu-Fei Wu. "Axial Strength of Eccentrically Loaded FRP-Confined Short Concrete Columns." Polymers 12, no. 6 (May 31, 2020): 1261. http://dx.doi.org/10.3390/polym12061261.
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This paper presents an experimental program that includes 78 fiber reinforced polymer (FRP)-confined square concrete columns subjected to eccentric loading. The degradation of the axial strength of FRP-confined short concrete columns due to the load eccentricity is investigated in this work. A larger load eccentricity leads to a greater decrease in the axial strength. From the test results, it is found that FRP confinement can cause less strength degradation compared with that of unconfined concrete specimens. For FRP-confined square concrete specimens, the strength enhancement due to FRP confinement increases with increasing load eccentricity. However, the increasing load eccentricity decreases the confinement efficiency for FRP-confined circular concrete specimens. The relationship between the strength of eccentrically loaded FRP-confined square columns and their corner radii is evaluated.
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Kamgar, Reza, Hosein Naderpour, Houman Ebrahimpour Komeleh, Anna Jakubczyk-Gałczyńska, and Robert Jankowski. "A Proposed Soft Computing Model for Ultimate Strength Estimation of FRP-Confined Concrete Cylinders." Applied Sciences 10, no. 5 (March 4, 2020): 1769. http://dx.doi.org/10.3390/app10051769.
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In this paper, the feed-forward backpropagation neural network (FFBPNN) is used to propose a new formulation for predicting the compressive strength of fiber-reinforced polymer (FRP)-confined concrete cylinders. A set of experimental data has been considered in the analysis. The data include information about the dimensions of the concrete cylinders (diameter, length) and the total thickness of FRP layers, unconfined ultimate concrete strength, ultimate confinement pressure, ultimate tensile strength of the FRP laminates and the ultimate concrete strength of the concrete cylinders. The confined ultimate concrete strength is considered as the output data, while other parameters are considered as the input data. These parameters are mostly used in existing FRP-confined concrete models. Soft computing techniques are used to estimate the compressive strength of FRP-confined concrete cylinders. Finally, a new formulation is proposed. The results of the proposed formula are compared to the existing methods. To verify the proposed method, results are compared with other methods. The results show that the described method can forecast the compressive strength of FRP-confined concrete cylinders with high precision in comparison with the existing formulas. Moreover, the mean percentage of error for the proposed method is very low (3.49%). Furthermore, the proposed formula can estimate the ultimate compressive capacity of FRP-confined concrete cylinders with a different type of FRP and arbitrary thickness in the initial design of practical projects.
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Cao, Yugui, Guoxu Zhao, Yang Zhang, Can Hou, and Ling Mao. "Unified Stress–Strain Model of FRP-Confined Square and Circle Rubber Concrete Columns." Materials 15, no. 5 (February 28, 2022): 1832. http://dx.doi.org/10.3390/ma15051832.
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Studying the stress–strain relationship of fiber-reinforced polymer (FRP)-confined rubber concrete (RuC) plays an important role in its application in engineering projects. Most of the existing stress–strain relationship models are established based on the test data of FRP-confined rubber concrete with circular cross-sections, and the effect of the section shape is not considered. Therefore, an analysis-oriented stress–strain model of FRP-confined circular and square rubber concrete columns was studied in this paper for the first time. A database that includes the rubber particle content and section shape on the peak stress-peak strain and axial–lateral strain relationship of FRP-confined rubber concrete was established by collecting 235 test data from the literature. By modifying the key parameters in the existing FRP-confined normal concrete stress–strain relationship model, a unified stress–strain relationship model of FRP-confined RuC with circular and square columns is established. The proposed model is verified, and a good accuracy of the model is proven.
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Vincent, Thomas, and Togay Ozbakkloglu. "An Experimental Study on the Compressive Behavior of CFRP-Confined High- and Ultra High-Strength Concrete." Advanced Materials Research 671-674 (March 2013): 1860–64. http://dx.doi.org/10.4028/www.scientific.net/amr.671-674.1860.
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It is well established that external confinement of concrete with fiber reinforced polymer (FRP) sheets results in significant improvements on the axial compressive behavior of concrete. This understanding has led to a large number of experimental studies being conducted over the last two decades. However, the majority of these studies have focused on normal strength concretes (NSC) with compressive strengths lower than 55 MPa, and studies on higher strength concretes have been very limited. This paper presents the results of an experimental study on the compressive behavior of FRP confined high- and ultra high-strength concrete (HSC and UHSC) with average compressive strengths of 65 and 100 MPa. A total of 29 specimens were tested under axial compression to investigate the influence of key parameters such as concrete strength and method of confinement. All specimens were cylindrical, confined with carbon FRP and were 305 mm in height and 152 mm in diameter. Results obtained from the laboratory testing were graphically presented in the form of axial stress-strain relationships and key experimental outcomes are discussed. The results of this experimental study indicate that above a certain confinement threshold, FRP-confined HSC and UHSC exhibit highly ductile behavior. The results also indicate that FRP-wrapped specimens perform similar to concrete-filled FRP tube (CFFT) specimens at ultimate condition, however notable differences are evident at the transition region when comparing stress-strain curves.
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Micelli, F., and J. J. Myers. "Durability of FRP-confined concrete." Proceedings of the Institution of Civil Engineers - Construction Materials 161, no. 4 (November 2008): 173–85. http://dx.doi.org/10.1680/coma.2008.161.4.173.
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Xie, Zhihong, Zhijian Duan, Yongchang Guo, Xiang Li, and Junjie Zeng. "Behavior of Fiber-Reinforced Polymer-Confined High-Strength Concrete under Split-Hopkinson Pressure Bar (SHPB) Impact Compression." Applied Sciences 9, no. 14 (July 16, 2019): 2830. http://dx.doi.org/10.3390/app9142830.
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Fiber-reinforced polymer (FRP) has become increasingly popular in repairing existing steel-reinforced concrete (RC) members or constructing new structures. Although the quasi-static axial compression performance of FRP-confined concrete (FCC) has been comprehensively studied, its dynamic compression performance is not well understood, especially the dynamic compressive behavior of FRP-confined high-strength concrete (FCHC). This paper presents an experimental program that consists of quasi-static compression tests and Split-Hopkinson Pressure Bar (SHPB) impact tests on FRP-confined high-strength concrete. The effects of the FRP types, FRP confinement stiffness, and strain rate on the impact resistance of FCHC are carefully studied. The experimental results show that the strain rate effect is evident for FRP-confined high-strength concrete and the existence of the FRP greatly improves the dynamic compressive strength of high-strength concrete. An existing strength model is modified for impact strength of FCHC and the predicted results are compared with the test results. The results and discussions show that the proposed model is accurate and superior to the existing models.
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De Diego, A., A. Arteaga, J. Fernández, R. Perera, and D. Cisneros. "Behaviour of FRP confined concrete in square columns." Materiales de Construcción 65, no. 320 (September 23, 2015): e069. http://dx.doi.org/10.3989/mc.2015.05414.
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Wei, Yang, Yang Xu, Gaofei Wang, Xunyu Cheng, and Guofen Li. "Influence of the Cross-Sectional Shape and Corner Radius on the Compressive Behaviour of Concrete Columns Confined by FRP and Stirrups." Polymers 14, no. 2 (January 16, 2022): 341. http://dx.doi.org/10.3390/polym14020341.
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Axial compression tests were carried out on 72 FRP (fiber reinforced polymer)–stirrup composite-confined concrete columns. Stirrups ensure the residual bearing capacity and ductility after the FRP fractures. To reduce the effect of stress concentration at the corners of the confined square-section concrete columns and improve the restraint effect, an FRP–stirrup composite-confined concrete structure with rounded corners is proposed. Different corner radii of the stirrup and outer FRP were designed, and the corner radius of the stirrup was adjusted accurately to meet the designed corner radius of the outer FRP. The cross-section of the specimens gradually changed from square to circular as the corner radius increased. The influence of the cross-sectional shape and corner radius on the compressive behaviour of FRP–stirrup composite-confined concrete was analysed. An increase in the corner radius can cause the strain distribution of the FRP to be more uniform and strengthen the restraint effect. The larger the corner radius of the specimen, the better the improvement of mechanical properties. The strength of the circular section specimen was greatly improved. In addition, the test parameters also included the FRP layers, FRP types and stirrup spacing. With the same corner radius, increasing the number of FRP layers or densifying the stirrup spacing effectively improved the mechanical properties of the specimens. Finally, a database of FRP–stirrup composite-confined concrete column test results with different corner radii was established. The general calculation models were proposed, respectively, for the peak points, ultimate points and stress–strain models that are applicable to FRP-, stirrup- and FRP–stirrup-confined concrete columns with different cross-sectional shapes under axial compression.
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Lim, Jian Chin, and Togay Ozbakkloglu. "A Simple Design-Oriented Model for FRP-Confined High-Strength Concrete." Advanced Materials Research 743 (August 2013): 45–49. http://dx.doi.org/10.4028/www.scientific.net/amr.743.45.
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This paper presents a study on the axial compressive behavior of fiber reinforced polymer (FRP)-confined high-strength concrete (HSC). A large experimental test database assembled from the published literature was used to investigate and quantify factors influencing the compressive behavior of FRP-confined HSC. The database consisted of 976 test data having unconfined concrete strength ranging from 6.2 to 169.7MPa. Based on the analysis results of the database, it was found that the threshold confinement stiffness increases significantly with an increase in concrete strength, which in turn adversely affects the strength enhancement of confined concrete. It was also observed that the hoop rupture strain of FRP shell decreases with an increase in concrete strength. Existing confinement models that are applicable to FRP-confined HSC were assessed using the database. Finally, a new simple design-oriented model for FRP-confined HSC developed on the basis of the database is presented.
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Long, Yue Ling, and Jiang Zhu. "Experimental Study on Concrete Columns with Various Sizes Confined by BFRP and Hybrid FRP under Axial Compression." Advanced Materials Research 838-841 (November 2013): 407–11. http://dx.doi.org/10.4028/www.scientific.net/amr.838-841.407.
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Fourteen concrete columns with various sizes confined by BFRP and hybrid FRP and six plain concrete columns as the control specimens were axially loaded to failure in order to investigate both confining effects and size effects in concrete columns confined by BFRP and hybrid FRP. Experimental results show that BFRP and hybrid FRP can increase considerably both the capacity and ductility of the concrete specimens. Furthermore, the peak stress of the unconfined concrete decreases with the size of the specimens increasing. Similarly, the peak stress of BFRP confined concrete decreases with the size of the specimens increasing when the lateral confining stresses are the same. Hence, both confining effect and size effects should be considered carefully in the stress-strain model of concrete confined by BFRP. In addition, both strength and ductility of concrete confined by hybrid FRP in case of CFRP as inner layers and BFRP as outward layers are better than those in case of BFRP as inner layers and CFRP as outward layers.
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Han, Yang Yang, Hao Zhang, Ya Qin Li, Jia Yao, and Xiao Ping Hu. "Experimental Study on Axial Compression of FRP Confined Concrete Column." Advanced Materials Research 461 (February 2012): 682–85. http://dx.doi.org/10.4028/www.scientific.net/amr.461.682.
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Abstract: Concrete members strengthened by fiber reinforced polymer (FRP) are increasingly becoming a popular retrofit technique in recent years due to the excellent material properties, convenient and easy construction methods, and outstanding strengthening effect. However, fundamental researches are incomplete; especially the characteristics research of square cross-section of FRP confined concrete has become a major obstacle for the development of further research and application. Therefore, the better understanding of the behavior of confined concrete becomes of paramount importance. A total of 10 concrete columns, which were reinforced with CFRP (carbon fiber reinforced polymer) and with filleted square sections, were fabricated and tested subjected to axial load to investigate the mechanical properties of FRP confined concrete. The mechanical behavior of FRP confined concrete has been further understood and some useful conclusions are obtained.
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Lim, Jian Chin, and Togay Ozbakkloglu. "Factors Influencing Hoop Rupture Strains of FRP-Confined Concrete." Applied Mechanics and Materials 501-504 (January 2014): 949–53. http://dx.doi.org/10.4028/www.scientific.net/amm.501-504.949.
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It is now well understood that the hoop rupture strain of fiber reinforced polymer (FRP) jackets confining concrete is often lower than the ultimate tensile strain of the component fibers. A number of reasons for the lower hoop rupture strains in FRP have been identified; however, the relationships between the material properties of FRP-confined concrete and hoop ruptures strains are yet to be established. This paper presents the results of an experimental study into the factors influencing the hoop strain efficiency of FRP jackets. 24 FRP-confined concrete specimens were tested under axial compression. The results indicate that the hoop rupture strains of FRP jackets decrease with either an increase in the strength of the unconfined concrete or the elastic modulus of the fiber material. These observations were verified by additional results from a large FRP-confined concrete test database assembled from the published literature.
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Abid, Muhammad, Haytham F. Isleem, Muhammad Kamal Kamal Shah, and Shayan Zeb. "Analytical Review on Eccentric Axial Compression Behavior of Short and Slender Circular RC Columns Strengthened Using CFRP." Polymers 13, no. 16 (August 17, 2021): 2763. http://dx.doi.org/10.3390/polym13162763.
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Although reinforced concrete (RC) columns subjected to combined axial compression and flexural loads (i.e., eccentric load) are the most common structural members used in practice, research on FRP-confined circular RC columns subjected to eccentric axial compression has been very limited. More specifically, the available eccentric-loading models were mainly based on existing concentric stress–strain models of FRP-confined unreinforced concrete columns of small scale. The strength and ductility of FRP-strengthened slender circular RC columns predicted using these models showed significant errors. In light of such demand to date, this paper presents a stress–strain model for FRP-confined circular reinforced concrete (RC) columns under eccentric axial compression. The model is mainly based on observations of tests and results reported in the technical literature, in which 207 results of FRP-confined circular unreinforced and reinforced concrete columns were carefully studied and analyzed. A model for the axial-flexural interaction of FRP-confined concrete is also provided. Based on a full parametric analysis, a simple formula of the slenderness limit for FRP-strengthened RC columns is further provided. The proposed model considers the effects of key parameters such as longitudinal and hoop steel reinforcement, level of FRP hoop confinement, slenderness ratio, presence of longitudinal FRP wraps, and varying eccentricity ratio. The accuracy of the proposed model is finally validated through comparisons made between the predictions and the compiled test results.
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Chen, Pang, Hui Wang, Shaojun Cao, and Xueyuan Lv. "Prediction of Mechanical Behaviours of FRP-Confined Circular Concrete Columns Using Artificial Neural Network and Support Vector Regression: Modelling and Performance Evaluation." Materials 15, no. 14 (July 17, 2022): 4971. http://dx.doi.org/10.3390/ma15144971.
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The prediction and control of the mechanical behaviours of fibre-reinforced polymer (FRP)-confined circular concrete columns subjected to axial loading are directly related to the safety of the structures. One challenge in building a mechanical model is understanding the complex relationship between the main parameters affecting the phenomenon. Artificial intelligence (AI) algorithms can overcome this challenge. In this study, 298 test data points were considered for FRP-confined circular concrete columns. Six parameters, such as the diameter-to-fibre thickness ratio (D/t) and the tensile strength of the FRP (ffrp) were set as the input sets. The existing models were compared with the test data. In addition, artificial neural networks (ANNs) and support vector regression (SVR) were used to predict the mechanical behaviour of FRP-confined circular concrete columns. The study showed that the predictive accuracy of the compressive strength in the existing models was higher than the peak compressive strain for the high dispersion of material deformation. The predictive accuracy of the ANN and SVR was higher than that of the existing models. The ANN and SVR can predict the compressive strength and peak compressive strain of FRP-confined circular concrete columns and can be used to predict the mechanical behaviour of FRP-confined circular concrete columns.
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Touhari, Mahfoud, and Ratiba Kettab Mitiche. "Strength model of FRP confined concrete columns based on analytical analysis and experimental test." International Journal of Structural Integrity 11, no. 1 (August 23, 2019): 82–106. http://dx.doi.org/10.1108/ijsi-04-2019-0040.
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Purpose Covering a fiber-reinforced concrete column (fiber reinforced plastic (FRP)) improves the performance of the column primarily. The purpose of this paper is to investigate the behavior of small FRP concrete columns that are subject to axial pressure loading, in order to study the effect of many parameters on the effectiveness of FRP couplings on circular and square concrete columns. Design/methodology/approach These parameters include the shape of the browser (circular and square), whole core and cavity, square radius of square columns, concrete strength (low strength, normal and high), type of FRP (carbon and glass) and number of FRP (1–3) layers. The effective fibrillation failure strain was investigated and the effect of effective lateral occlusion pressure. Findings The results of the test showed that the FRP-coated columns improved significantly the final conditions of both the circular and square samples compared to the unrestricted columns; however, improvement of square samples was not as prominent as improvement in circular samples. The results indicated that many parameters significantly affected the behavior of FRP-confined columns. A new model for predicting compressive force and the corresponding strain of FRP is presented. A good relationship is obtained between the proposed equations and the current experimental results. Originality/value The average hoop strain in FRP wraps at rupture in FRP-confined concrete specimens can be much lower than that given by tensile coupon tests, meaning the theoretical assumption that the FRP-confined concrete cylinder ruptures when the FRP material tensile strength attained at its maximum is not suitable. Based on this observation, the effective peak strength and corresponding strain formula for FRP concrete confined columns must be based on the effective hoop rupture strain composite materials.
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Raza, Ali, Syyed Adnan Raheel Shah, Ahsan Rehman Khan, Muhammad Asif Aslam, Tanveer Ahmed Khan, Kinza Arshad, Sabahat Hussan, Asad Sultan, Gullnaz Shahzadi, and Muhammad Waseem. "Sustainable FRP-Confined Symmetric Concrete Structures: An Application Experimental and Numerical Validation Process for Reference Data." Applied Sciences 10, no. 1 (January 2, 2020): 333. http://dx.doi.org/10.3390/app10010333.
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The use of fiber-reinforced polymer (FRP) jackets as external confinement is becoming popular, especially in seismic areas, because of its ability to enhance the strength and ductility of reinforced concrete to perform as a sustainable symmetric structural member. Therefore, various researchers have worked out for the prediction of strength and strain models of FRP-confined concrete. This study presents the improved strain models for the FRP confined cylindrical concrete members. Different previously proposed models of axial strain of FRP-confined concrete were evaluated based on a large database of 678 specimens from previous experiments and an improved model was proposed using the general regression analysis technique. Furthermore, the proposed model was validated using the previous experimental work of FRP-wrapped concrete cylinders and their finite elements analysis (FEA) using the ABAQUS software. The accuracy of the proposed strain model was quite satisfactory in comparison with the previous experimental and FEA results of the present study. Moreover, the proposed empirical strain model was used for the parametric study to investigate the effect of different geometric and material parameters such as the compressive strength of unconfined concrete, diameter of the cylinder, elastic modulus and thickness of the FRP layers, on the axial strain of FRP-wrapped cylinders. A close agreement among the proposed strain models and experimental outputs was observed. This study will help in understanding the behavior of sustainable FRP-confined symmetric concrete members.
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Abbassi, Muhammad, and Hooshang Dabbagh. "Seismic Response of Reactive Powder Concrete Columns Confined with FRP." Slovak Journal of Civil Engineering 27, no. 3 (September 1, 2019): 12–20. http://dx.doi.org/10.2478/sjce-2019-0017.
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Abstract In this research, which is based on the finite element method, the behavior of reactive powder concrete (RPC) columns confined with fiber-reinforced polymer (FRP) under seismic excitation is investigated. The governing theory in the numerical simulation is based on the fiber finite element method. The adequacy of the fiber model in predicting the response of FRP-confined RPC columns is validated through comparisons with the available experimental results. To study the seismic behavior of FRP-confined RPC columns, the fiber model presented was subjected to different earthquakes. In this regard, four ground acceleration time histories with different peak accelerations were applied to investigate the response of FRP-confined RPC columns. The results show that reactive powder concrete columns confined with FRP exhibit an acceptable seismic performance. The investigation also confirms that RPC-confined columns show a high degree of ductility. Additionally, the load capacity (maximum lateral load) is increased, and the concrete’s compressive strength is increased.
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Gora, Abdurra’uf M., Jayaprakash Jaganathan, M. P. Anwar, and H. Y. Leung. "Experimental studies and theoretical models for concrete columns confined with FRP composites: a review." World Journal of Engineering 16, no. 4 (June 12, 2019): 509–25. http://dx.doi.org/10.1108/wje-01-2018-0026.
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Purpose Advanced fibre-reinforced polymer (FRP) composites have been increasingly used over the past two decades for strengthening, upgrading and restoring degraded civil engineering infrastructure. Substantial experimental investigations have been conducted in recent years to understand the compressive behaviour of FRP-confined concrete columns. A considerable number of confinement models to predict the compressive behaviour of FRP-strengthened concrete columns have been developed from the results of these experimental investigations. The purpose of this paper is to present a comprehensive review of experimental investigations and theoretical models of circular and non-circular concrete columns confined with FRP reinforcement. Design/methodology/approach The paper reviews previous experimental test results on circular and non-circular concrete columns confined with FRP reinforcement under concentric and eccentric loading conditions and highlights the behaviour and mechanics of FRP confinement in these columns. The paper also reviews existing confinement models for concrete columns confined with FRP composites in both circular and non-circular sections. Findings This paper demonstrates that the performance and effectiveness of FRP confinement in concrete columns have been extensively investigated and proven effective in enhancing the structural performance and ductility of strengthened columns. The strength and ductility enhancement depend on the number of FRP layers, concrete compressive strength, corner radius for non-circular columns and intensity of load eccentricity for eccentrically loaded columns. The impact of existing theoretical models and directions for future research are also presented. Originality/value Potential researchers will gain insight into existing experimental and theoretical studies and future research directions.
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Gholampour, Aliakbar, and Togay Ozbakkaloglu. "Finite Element Analysis of Constitutive Behavior of FRP-Confined Steel Fiber Reinforced Concrete." Key Engineering Materials 737 (June 2017): 511–16. http://dx.doi.org/10.4028/www.scientific.net/kem.737.511.
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This study presents the analysis of the constitutive behavior of fiber-reinforced polymer (FRP)-confined steel fiber reinforced concrete (SFRC) using a newly developed concrete damage-plasticity approach. Finite element (FE) analysis is conducted based on Lubliner’s model. The new concrete damage-plasticity approach accurately incorporates the effects of the steel fiber volume fraction and aspect ratio, confinement level, concrete strength, and nonlinear dilation behavior of confined concrete. New failure surface and flow rule were established using the experimental database. In order to validate the damage-plasticity model, the predictions from the FE analysis are compared with both experimental results and predictions of an accurate existing model for FRP-confined plain concrete. The analysis results indicate that the proposed approach accurately predicts the compressive behavior of FRP-confined SFRC.
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Mortazavi, Ali A., and Mostafa Jalal. "Investigation of CFRP- and GFRP-confined concrete cylinders under monotonic and cyclic loading." Science and Engineering of Composite Materials 21, no. 4 (September 1, 2014): 607–14. http://dx.doi.org/10.1515/secm-2013-0213.
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AbstractFiber reinforced polymer (FRP) composites have found increasingly wide applications in engineering due to their high strength-to-weight ratio and high corrosion resistance. One important application of FRP composites is as a confining material for concrete, which can enhance both the compressive strength and the ultimate axial strain of concrete. With this respect, the stress-strain behavior of FRP-confined concrete, under both monotonic and cyclic compression, needs to be properly understood and modeled. This paper presents details of an experimental work carried out on concrete cylinders wrapped with FRP materials and subjected to both monotonic and cyclic loading. A total number of 12 FRP confined concrete specimens and 10 control specimens with a diameter of 100 mm and a height of 200 mm were cast and cured under the same conditions, and two FRP materials (carbon fibers (CFRP) and glass fibers (GFRP)) were used for the construction of the FRP jackets. The effect of the type of confinement material, reinforcement ratio based on the jacket stiffness, and type of loading is examined. A model that predicts the behavior of confined concrete, which takes into account the stiffness and effectiveness of different confinement materials is also briefly introduced.
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Benzaid, Riad, and Habib-Abdelhak Mesbah. "THE CONFINEMENT OF CONCRETE IN COMPRESSION USING CFRP COMPOSITES – EFFECTIVE DESIGN EQUATIONS." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 20, no. 5 (October 20, 2014): 632–48. http://dx.doi.org/10.3846/13923730.2013.801911.
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This paper presents the results of an experimental study on the behaviour of axially loaded short concrete columns, with different cross sections that have been externally strengthened with carbon fibre-reinforced polymer (CFRP) sheets. Six series, forming the total of 60 specimens, were subjected to axial compression. All the test specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. According to the obtained test results, FRP-confined specimen failure occurs before the FRP reached the ultimate strain capacities. Thus, the failure occurs prematurely and the circumferential failure strain is lower than the ultimate strain obtained from the standard tensile testing of the FRP composite. In existing models for FRP-confined concrete, it is commonly assumed that the FRP ruptures when the hoop stress in the FRP jacket reaches its tensile strength from either flat coupon tests, which is herein referred to as the FRP material tensile strength. This phenomenon considerably affects the accuracy of the existing models for FRP-confined concrete. On the basis of the effective lateral confining pressure of the composite jacket and the effective circumferential FRP failure strain, new equations were proposed to predict the strength of FRP-confined concrete and corresponding strain for each of the cross section geometry used, circular and square. The estimations given by these equations were compared with the experimental ones and general conclusions were drawn.
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Yang, Junlong, Jizhong Wang, and Ziru Wang. "Design-oriented axial stress–strain model for partially fiber-reinforced-polymer-confined normal-strength concrete." Advances in Structural Engineering 23, no. 16 (July 14, 2020): 3481–95. http://dx.doi.org/10.1177/1369433220933461.
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Due to the influence of “arching action” in fiber-reinforced polymer (FRP) partially confined concrete columns as a result of the unconfined regions, the confinement of the concrete columns wrapped with discrete FRP strips is less efficient when compared with full wrapping schemes. This study comprehensively investigates the difference of the the confinement mechanism between fully and partially FRP confined circular normal-strength concrete and thus presents a new design-oriented model to predict the stress–strain relationships of partially FRP confined normal-strength concrete. The formulas used to determine the strength and corresponding strain of several key points on the stress–strain curves are also proposed by the regression analysis according to a reliable test database from the relevant literature. Besides, another selected database including 100 FRP partially wrapped circular concrete columns is also collected for model verification. The results show that better performance can be achieved by the new model compared with the selected models in predicting the ultimate conditions of partially FRP confined concrete. Finally, some specimens are chosen to assess the performance of the new model in predicting the complete axial stress–strain curves. The comparisons reveal that satisfactory accuracy and good agreement can be achieved between the theoretical predictions and experimental observations.
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Guo, Yong-Chang, Shu-Hua Xiao, Jun-Wei Luo, Yu-Yi Ye, and Jun-Jie Zeng. "Confined Concrete in Fiber-Reinforced Polymer Partially Wrapped Square Columns: Axial Compressive Behavior and Strain Distributions by a Particle Image Velocimetry Sensing Technique." Sensors 18, no. 12 (November 23, 2018): 4118. http://dx.doi.org/10.3390/s18124118.
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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.
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Csuka, Bernát, and László Kollár. "Concentrically loaded FRP confined concrete columns." Építés - Építészettudomány 38, no. 1-2 (March 2010): 5–34. http://dx.doi.org/10.1556/eptud.38.2010.1-2.1.
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Ghosh, Subha, and Arghya Deb. "Mesoscale Model for FRP-Confined Concrete." Journal of Materials in Civil Engineering 32, no. 6 (June 2020): 04020123. http://dx.doi.org/10.1061/(asce)mt.1943-5533.0003155.
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Zhu, Tian Zhi, Ming Zhang, and Yan Ying Dong. "Research on Cross-Sectional Area Converting Principle Based Model of FRP Confined Concrete Axial Compressive Strength." Advanced Materials Research 243-249 (May 2011): 5541–46. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.5541.
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Fiber reinforced plastics (FRP) has been widely used in structure reinforcement processing. It is a comparatively mature field in computational models of cylindrical axial compressive strength on FRP confined concrete. In this paper, we conduct a possessive analysis on the axial compressive property that is based on the cylindrical stress model of FRP confined concrete, considering the difference among square column section, rectangular column and cylindrical column. Meanwhile, based on cross-sectional area and moment of inertia equivalent principles, we propose an equivalent diameter formula for converting rectangular column section into cylindrical column section. We also introduce sectional influence coefficients to modify ultimate strength and establish a model of ultimate strength for FRP confined concrete. Furthermore, we use the existing experimental data to test the validity and feasibility of the model. Experimental Results of the computational model are quite coincident and consistent with the tests. Computational model can reflect the true characteristics of FRP confined concrete. Therefore, the models proposed in this paper are significant in the practice of construction project.
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Alzeebaree, Radhwan, Abdulkadir Çevik, Alaa Mohammedameen, Anıl Niş, and Mehmet Eren Gülşan. "Mechanical performance of FRP-confined geopolymer concrete under seawater attack." Advances in Structural Engineering 23, no. 6 (November 14, 2019): 1055–73. http://dx.doi.org/10.1177/1369433219886964.
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In the study, mechanical properties and durability performance of confined/unconfined geopolymer concrete and ordinary concrete specimens were investigated under ambient and seawater environments. Some of the specimens were confined by carbon fiber and basalt fiber–reinforced polymer fabric materials with one layer and three layers under chloride and ambient environments to observe mechanical strength contribution and durability performances of these hybrid types of materials. These fiber-reinforced polymer fabric materials were also evaluated in terms of retrofit purposes especially in the marine structures. In addition, microstructural evaluation is also conducted using scanning electron microscope on geopolymer concrete and ordinary concrete specimens to observe the amount of deterioration in microscale due to the chloride attacks. Results indicated that confined specimens exhibited enhanced strength, ductility, and durability properties than unconfined specimens, and the degree of the enhancement depended on the fiber-reinforced polymer confinement type and the number of fiber-reinforced polymer layer. Specimens confined by carbon fabrics with three layers showed superior mechanical properties and durability performance against chloride attack, while specimens confined by basalt fabrics with one layer exhibited low performance, and unconfined specimens showed the worst performance. Both fiber-reinforced polymer fabric materials can be utilized as retrofit materials in structural elements against chloride attacks. The results also pointed out that seawater attack reduced the ductility performance of the geopolymer concrete and ordinary concrete specimens. Furthermore, geopolymer concrete specimens were found more durable than the ordinary concrete specimens, and both types of concretes exhibited similar fracture properties, indicating that geopolymer concrete can be utilized for structural elements instead of ordinary concretes.
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Vincent, Thomas, and Togay Ozbakkloglu. "The Effect of Confinement Method and Specimen End Condition on Behavior of FRP-Confined Concrete under Concentric Compression." Applied Mechanics and Materials 351-352 (August 2013): 650–53. http://dx.doi.org/10.4028/www.scientific.net/amm.351-352.650.
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This paper presents an experimental investigation on the influence of confinement method and specimen end condition on axial compressive behavior of fiber reinforced polymer (FRP)-confined concrete. A total of 12 aramid FRP (AFRP)-confined concrete specimens with circular cross-sections were tested. Half of these specimens were manufactured as concrete-filled FRP tubes (CFFTs) and the remaining half were FRP-wrapped concrete cylinders. The effect of specimen end condition was examined on both CFFTs and FRP-wrapped specimens. This parameter was selected to study the influence of loading the FRP jacket on the axial compressive behavior. In this paper the experimentally recorded stress-strain relationships are presented graphically and key experimental outcomes discussed. The results indicate that the performance of FRP-wrapped specimens is similar to that of CFFT specimens and the influence of specimen end condition is negligible.
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Manoj, Aiswarya, and Dhanya Sathyan. "Strengthening of concrete square column using FRP composites." Journal of Physics: Conference Series 2070, no. 1 (November 1, 2021): 012206. http://dx.doi.org/10.1088/1742-6596/2070/1/012206.
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Abstract Strength and energy absorption capacity are the important parameter for axially loaded column. This paper investigates the strength of unconfined square concrete column and externally confined square column with fiber-reinforced (FRP) composites with synthetic carbon fiber and natural banana fiber. This type of strengthening of column is widely accepted in practice. Axial strength test is performed on confined square column with different parameters such as number of layers of FRP materials, wrapping patters like full wrapping, center wrapping and hybrid pattern. Both natural and synthetic fibers are used for FRP-confined square concrete column. It was found that external confinement using FRP material improved the axial-load carrying capacity, load-deformation and ductility of the square column compared to the unconfined square column.
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Wang, Xuxu, Yujun Qi, Yunlou Sun, Zhijin Xie, and Weiqing Liu. "Compressive Behavior of Composite Concrete Columns with Encased FRP Confined Concrete Cores." Sensors 19, no. 8 (April 15, 2019): 1792. http://dx.doi.org/10.3390/s19081792.
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A composite concrete column with encased fiber reinforced polymer (FRP) confined concrete cores (EFCCC) is proposed in this paper. The cross-sectional form of the EFCCC column is composed of several orderly arranged FRP confined concrete cores (FCCCs) surrounding a filled core concrete. This novel composite column has several advantages, such as higher compressive capacity, stronger FRP confinement, and ductile response. The compressive experiment is employed to investigate the compressive behavior of the EFCCC column with deferent parameters, such as outside concrete and stirrups. Test results show that the main failure mode of the EFCCC column with and without an outside concrete or stirrups is tensile fracture of the glass fiber reinforced polymer (GFRP) tubes. Compared to a reinforced concrete (RC) column, the strength and ductility of the EFCCC column was obviously improved by 20% and 500%, respectively. A finite element model (FEM) based on the Drucker–Prager (D-P) was developed that can accurately predict the axial compression behavior of the composite column with FRP confined concrete core. The predicted results obtained by using this FEM have excellent agreement with the experimental results.
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Salesa, A., L. M. Esteban, and C. Barris. "Confinement of FRP concrete columns: Review of design guidelines and comparison with experimental results." Materiales de Construcción 72, no. 345 (March 1, 2022): e274. http://dx.doi.org/10.3989/mc.2022.03821.
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A regulatory framework is required to ensure the correct design of Fibre-Reinforced Polymers (FRPs) increasingly being used as an externally-bonded strengthening system on concrete columns. Several design guidelines on the confinement of FRP concrete have been developed over the past few years worldwide, each proposing a different approach, resulting in different predictions. This study aims to evaluate and compare nine international design guidelines used to predict the compressive strength of confined concrete in FRP-strengthened concrete columns and weigh them against experimental results. The results of this investigation reveal that the predictions from the guidelines on the compressive strengthening of FRP-confined concrete are generally suitable for circular columns, with the ACI-440 and CNR-DT 200 guideline predictions being two of the most accurate. Nevertheless, the guidelines generally tend to overestimate the load-carrying capacity for the compressive strength of FRP-confined concrete in non-circular columns, for which further experimental work using large-scale specimens is required.
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Dong, Jing, Junhai Zhao, Dongfang Zhang, and Yingping Li. "Research on Dynamic Response of Concrete-Filled Steel Tube Columns Confined with FRP under Blast Loading." Shock and Vibration 2019 (July 10, 2019): 1–18. http://dx.doi.org/10.1155/2019/8692310.
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Recently, a concrete-filled steel tube confined with fiber-reinforced polymer (FRP) has become a hot research issue as a new type of structure. These studies mainly focus on its static performance and seismic and impact behaviour, with little research on its blast resistance performance. In this study, the dynamic response of concrete-filled steel tube columns confined with FRP under blast loading was investigated. Numerical analysis was implemented using multimaterial ALE method in the finite element analysis program LS-DYNA. The proposed numerical model was validated by the SDOF result and available experimental data. And the effects of the number of FRP layers, concrete strength, and cross section were also discussed in detail based on the proposed numerical model. The results indicate that the constraints of FRP effectively enhance the blast resistance of the column, and the vulnerable parts mainly occur at the middle and two ends of the column. The blast resistance of the column can be enhanced by increasing the number of FRP layers or concrete strength. These results could provide a certain basis for blast resistance design of concrete-filled steel tubes confined with FRP.
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Shao, Yun Da, and Hong Guo. "Analysis and Summary of Characteristics of Confined Concrete." Applied Mechanics and Materials 174-177 (May 2012): 330–35. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.330.
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Characteristics and constraint mechanism of concrete confined by ties,concrete filled steel tube,FRP-strengthened concrete were summed up in this paper,and unified bearing capacity model for confined concrete was also introduced,then several new kinds of confined concrete forms were outlined,finally the development and application of confined concrete were prospected.
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Yu, Bao Chu, Hong Bai Gai, and Yun Yu Li. "A Kind of New Type Composite Structure Column of Research." Advanced Materials Research 634-638 (January 2013): 2653–56. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.2653.
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Steel tube confined concrete structure and FRP-confined concrete structure were researched and widely applied in structure engineering current years. Based on the advantage and disadvantage of the two types of structure, a new type of structure named FRP-steel composite pipe confined concrete is proposed. Moreover, the feasible and advantageous about the application of this new type in structure engineering is stated. The development prospects of this new type of structure are mentioned as well.
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Li, Pengda, Lili Sui, Feng Xing, Xiaoxu Huang, Yingwu Zhou, and Yanchun Yun. "Effects of Aggregate Types on the Stress-Strain Behavior of Fiber Reinforced Polymer (FRP)-Confined Lightweight Concrete." Sensors 18, no. 10 (October 18, 2018): 3525. http://dx.doi.org/10.3390/s18103525.
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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.
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Liu, Ming Hui, Yuan Feng Wang, and Han Liang Wu. "Five-Phase Sphere Model for Elastic Modulus of FRP-Confined Concrete." Applied Mechanics and Materials 204-208 (October 2012): 3707–11. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.3707.
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Based on the four-phase sphere model, a five-phase sphere model predicting the elastic modulus of FRP-confined concrete was built up, by considering the effect of FRP sheet. The model can describe the elastic modulus of the FRP, the stirrup ratio, the aggregate volume fraction, the aggregate size and the interfacial transition zone (ITZ), et al. on the development of the elastic modulus of FRP-confined concrete with age. By comparing with the experimental data, the five-phase sphere model evaluates the tests well
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Li, Ben-ben, Hai-bei Xiong, Jia-fei Jiang, and Yang Zhan. "Damage plasticity model for passively confined concrete." MATEC Web of Conferences 275 (2019): 02016. http://dx.doi.org/10.1051/matecconf/201927502016.
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This paper presents a modified concrete damage plasticity model (CDPM) for passively confined concrete within the concrete damage plasticity theory frame in ABAQUS. The modified CDPM can be used to simulate concrete under non-uniform passive confinement, for example, Fiber-reinforced polymer (FRP)-confined square concrete columns. The modification of CDPM includes a flow rule and a strain hardening/softening criterion in which dilation angle and yield stress are important parameters. Based on the true-triaxial experiment results of passively confined concrete, the dilation angle and yield stress were determined considering different confinement stiffness and non-uniform confinement stiffness ratio. Finally, the modified CDPM were incorporated in the ABAQUS model. The prediction of the finite element model of FRP-confined square concrete columns shows good prediction accuracy.
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Kaeseberg, Stefan, Dennis Messerer, and Klaus Holschemacher. "Experimental Study on Concrete under Combined FRP–Steel Confinement." Materials 13, no. 20 (October 9, 2020): 4467. http://dx.doi.org/10.3390/ma13204467.
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The confinement of reinforced concrete (RC) compression members by fiber-reinforced polymers (FRPs) is an effective measure for the strengthening and retrofitting of existing structures. Thus far, extensive research on the stress–strain behavior and ultimate limit state design of FRP-confined concrete has been conducted, leading to various design models. However, these models are significantly different when compared to one another. In particular, the use of certain empirical efficiency and reduction factors results in various predictions of load-bearing behavior. Furthermore, most experimental programs solely focus on plain concrete specimens or demonstrate insufficient variation in the material properties. Therefore, this paper presents a comprehensive experimental study on plain and reinforced FRP-confined concrete, limited to circular cross sections. The program included 63 carbon FRP (CFRP)-confined plain and 60 CFRP-confined RC specimens with a variation in the geometries and in the applied materials. The analysis showed a significant influence of the compressive strength of the confined concrete on the confinement efficiency in the design methodology, as well as the importance of the proper determination of individual reduction values for different FRP composites. Finally, applicable experimental test results from the literature were included, enabling the development of a modified stress–strain and ultimate condition design model.
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Moodi, Yaser, Mohammad Ghasemi, and Seyed Roohollah Mousavi. "Estimating the compressive strength of rectangular fiber reinforced polymer–confined columns using multilayer perceptron, radial basis function, and support vector regression methods." Journal of Reinforced Plastics and Composites 41, no. 3-4 (October 19, 2021): 130–46. http://dx.doi.org/10.1177/07316844211050168.
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Recently, there has been a tendency to use machine learning (ML)–based methods, such as artificial neural networks (ANNs), for more accurate estimates. This paper investigates the effectiveness of three different machine learning methods including radial basis function neural network (RBNN), multi-layer perceptron (MLP), and support vector regression (SVR), for predicting the ultimate strength of square and rectangular columns confined by various FRP sheets. So far, in the previous study, several experiments have been conducted on concrete columns confined by fiber reinforced polymer (FRP) sheets with the results suggesting that the use of FRP sheets enhances the compressive strength of concrete columns effectively. Also, a wide range of experimental data (including 463 specimens) has been collected in this study for square and rectangular columns, confined by various FRP sheets. The comparison of ML-derived results with the experimental findings, which were in a very good agreement, demonstrated the ability of ML to estimate the compressive strength of concrete confined by FRP; the correlation coefficient (R2) for MLP, RBFNN, and SVR methods was equal to 0.97, 0.97, and 0.90, respectively. Similar accuracy was obtained by MLP and RBFNN, and they provided better estimates for determining the compressive strength of concrete confined by FRP. Also, the results showed that the difference between statistical indicators for training and testing specimens in the RBFNN method was greater than the MLP method, and this difference indicated the poor performance of RBFNN.
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Palanivel, S., and M. Sekar. "Cyclic Behaviour of GFRP and Lateral Ties Confined Polyolefin Fibre Reinforced Concrete under Axial Repeated Compression." Applied Mechanics and Materials 275-277 (January 2013): 1330–34. http://dx.doi.org/10.4028/www.scientific.net/amm.275-277.1330.
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Confinement by fiber reinforced polymer (FRP) wraps can significantly enhance strength and ductility of concrete. Although various models exist for envelope curves of concrete confined by transverse reinforcement and FRP, only a few simple models represent the hysteretic behavior of the confined concrete; therefore, development of stress–strain model of unloading and reloading paths for confined concrete is needed. In this paper, an experimental and numerical investigation for describing the cyclic stress–strain behavior of lateral ties and FRP confined polyolefin fibre reinforced concrete (FRPCFRC) prisms under repeated axial compressive loading is presented. The study focuses on the effect of repeated unloading and reloading cycles on confined concrete prisms. The combined effect of spacing of lateral ties, FRP wraps and volume fraction of polyolefin fibres was studied both experimentally and numerically from the point of deformability characteristics of concrete under repeated loading as loading, unloading and reloading.The envelope curve is derived from the results of uniaxial, monotonic, compression loading tests on specimens. It explicitly accounts for the effects of lateral tie spacing of 145mm spacing and 75mm spacing, single layer of woven roving(GFRP) and polyolefin fibres of volume fractions 0.7% and 1.2% on concrete prisms of size 150 ×150 ×300 mm were investigated. The behaviour was also simulated in finite element numerical model in ANSYS software, with a view to analyzing FRPCFRC prisms under repeated loading. This analysis accounts for energy dissipation through hysteretic behavior, stiffness degradation as damage progresses, and degree of confinement. It was observed from hysteretic behavior that for increased confinement by FRP wraps and addition of polyolefin fibres the degradation of strength and stiffness reduces significantly.
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Isleem, Haytham F., Muhammad Abid, Wesam Salah Alaloul, Muhammad Kamal Shah, Shayan Zeb, Muhammad Ali Musarat, Muhammad Faisal Javed, Fahid Aslam, and Hisham Alabduljabbar. "Axial Compressive Strength Models of Eccentrically-Loaded Rectangular Reinforced Concrete Columns Confined with FRP." Materials 14, no. 13 (June 23, 2021): 3498. http://dx.doi.org/10.3390/ma14133498.
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The majority of experimental and analytical studies on fiber-reinforced polymer (FRP) confined concrete has largely concentrated on plain (unreinforced) small-scale concrete columns, on which the efficiency of strengthening is much higher compared with large-scale columns. Although reinforced concrete (RC) columns subjected to combined axial compression and flexural loads (i.e., eccentric compression) are the most common structural elements used in practice, research on eccentrically-loaded FRP-confined rectangular RC columns has been much more limited. More specifically, the limited research has generally been concerned with small-scale RC columns, and hence, the proposed eccentric-loading stress-strain models were mainly based on the existing concentric-loading models of FRP-confined concrete columns of small scale. In the light of such demand to date, this paper is aimed at developing a mathematical model to better predict the strength of FRP-confined rectangular RC columns. The strain distribution of FRP around the circumference of the rectangular sections was investigated to propose equations for the actual rupture strain of FRP wrapped in the horizontal and vertical directions. The model was accomplished using 230 results of 155 tested specimens compiled from 19 studies available in the technical literature. The test database covers an unconfined concrete strength ranging between 9.9 and 73.1 MPa, and section’s dimension ranging from 100–300 mm and 125–435 mm for the short and long sides, respectively. Other test parameters, such as aspect ratio, corner radius, internal hoop steel reinforcement, FRP wrapping layout, and number of FRP wraps were all considered in the model. The performance of the model shows a very good correlation with the test results.
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LI, S. Q., J. F. CHEN, L. A. BISBY, Y. M. HU, and J. G. TENG. "STRAIN EFFICIENCY OF FRP JACKETS IN FRP-CONFINED CONCRETE-FILLED CIRCULAR STEEL TUBES." International Journal of Structural Stability and Dynamics 12, no. 01 (January 2012): 75–94. http://dx.doi.org/10.1142/s0219455412004574.
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The confinement of concrete columns using fiber-reinforced polymer (FRP) jackets or wraps is a popular structural retrofitting technique. More recently, the benefits of FRP confinement of concrete-filled steel tubes have also been explored by researchers. Failure of such FRP-confined concrete-filled steel tubes is usually governed by the rupture of the FRP jacket in the hoop direction. However, the observed FRP hoop strain at failure (i.e. the hoop rupture strain) is typically lower than the ultimate tensile strain from a flat coupon test. Many factors may contribute to this phenomenon, one of which is the geometrical discontinuities at both the starting and finishing ends of the wrapping process commonly used to form an FRP jacket. This paper examines the effect of these geometrical discontinuities on the hoop rupture strain of FRP jackets in FRP-confined concrete-filled circular steel tubes. Detailed finite element (FE) analyses conducted using both linear elastic and elastic-perfectly plastic adhesive constitutive models are presented. Comparison between the FE predictions and available test results shows that the hoop rupture strains of FRP jackets predicted by FE analysis using an elastic-perfectly plastic adhesive model are in reasonable agreement with the test results. The influence of parameters such as the FRP thickness, FRP orthotropy, FRP elastic modulus, adhesive yield strength, adhesive thickness, and column size are examined.
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Isleem, Haytham, and Zhenyu Wang. "Axial Compressive Stress-Strain Model Developed for FRP-Confined Concrete Columns with Elliptical Cross Sections." Journal of Composites Science 2, no. 4 (November 27, 2018): 67. http://dx.doi.org/10.3390/jcs2040067.
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Most existing studies conducted on fiber-reinforced polymer (FRP)-confined concrete have considered circular and square concrete columns, while limited studies have considered columns with rectangular sections. Studies have confirmed that the circular cross-sections exhibited higher confinement effectiveness, whereas in the case of non-circular cross-sections the efficiency of FRP confinement decreases with an increase of the sectional aspect ratio and there is no significant increase, particularly for columns with the aspect ratio of 2.0. As recently suggested by researchers, to significantly increase the effectiveness of FRP-confinement for these columns involves changing a rectangular section into an elliptical or oval section. According to the literature, most of the existing confinement models for FRP-confined concrete under axial compression have been proposed for columns with circular and rectangular cross-sections. However, modeling of the axial strength and strain of concrete confined with FRP in elliptical cross-sections under compression is limited. Therefore, this paper provides new expressions based on limited experimental data available in the literature. For a sufficient amount of FRP-confinement, the threshold value was proposed to be 0.02. Finally, the accuracy of the proposed model was verified by comparing its predictions with the same test database, together with those from the existing models.