Research

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16 pages, 5578 KiB

Open AccessArticle

Strengthening of Precast RC Frame to Mitigate Progressive Collapse by Externally Anchored Carbon Fiber Ropes

by Jianwu Pan, Xian Wang and Hao Dong

Polymers 2021, 13(8), 1306; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13081306 - 16 Apr 2021

Cited by 6 | Viewed by 1703

The robustness of precast reinforced concrete (RC) frames is relatively poor, while the precast RC frames are strengthened to mitigate progressive collapse, avoiding “strong beams and weak columns” and the anchorage failure of strengthening materials under large deformation condition are the key problems. [...] Read more.

The robustness of precast reinforced concrete (RC) frames is relatively poor, while the precast RC frames are strengthened to mitigate progressive collapse, avoiding “strong beams and weak columns” and the anchorage failure of strengthening materials under large deformation condition are the key problems. Aiming to discuss these problems, this paper carried out an experimental research of strengthening on three half-scale assembled monolithic frame subassemblages to mitigate progressive collapse. One specimen was strengthened by implanting carbon fiber rope (CFR) with polymer into concrete, one specimen was strengthened by binding CFR with special knot, and the last one was not strengthened. The failure mode, collapse failure mechanism and strengthening effect of subassemblages were discussed. Analytical models of load capacity increment contributed by CFR and construction suggestions of precast RC frame to mitigate progressive collapse were proposed. The results indicated that none of the strengthened specimens had anchorage failure. The two strengthening methods significantly increased the load capacity of the subassemblages in the catenary action (CA) stage with little effect on the flexural action (FA) stage and compressive arch action (CAA) stage. Full article

(This article belongs to the Special Issue Advances and Challenges in Utilizing Fiber-Reinforced Polymer (FRP) in Construction)

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33 pages, 7515 KiB

Open AccessArticle

Strength Profile Pattern of FRP-Reinforced Concrete Structures: A Performance Analysis through Finite Element Analysis and Empirical Modeling Technique

by Ali Raza, Syyed Adnan Raheel Shah, Hatem Alhazmi, Muhammad Abrar and Samia Razzaq

Polymers 2021, 13(8), 1265; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13081265 - 13 Apr 2021

Cited by 11 | Viewed by 2217

Abstract

Limited research work is available in the literature for the theoretical estimates of axial compressive strength of columns reinforced with fiber reinforced polymer (FRP) rebars. In the present work, an experimental database of 278 FRP-reinforced concrete (RC) compression members was established from the [...] Read more.

Limited research work is available in the literature for the theoretical estimates of axial compressive strength of columns reinforced with fiber reinforced polymer (FRP) rebars. In the present work, an experimental database of 278 FRP-reinforced concrete (RC) compression members was established from the literature to recommend an empirical model that can accurately predict the axial strength (AS) of GFRP-RC specimens. An initial assessment of 13 different previously anticipated empirical models was executed to achieve a general form of the AS model. Finally, a new empirical equation for forecasting the AS of GFRP-RC short columns was proposed using the curve fitting and regression analysis technique. The performance of the proposed empirical model over the previous experimental database represented its higher accuracy as related to that of other models. For the further justification of the anticipated model, a numerical model of GFRP-RC columns was simulated using ABAQUS and a wide parametric study of 600 GFRP-RC samples was executed to generate a numerical database and investigate the influence of various parameters using numerical and empirical models. The comparison between theoretical and numerical predictions with R² = 0.77 indicted that the anticipated empirical model is accurate enough to apprehend the AS of FRP-RC specimens. Full article

(This article belongs to the Special Issue Advances and Challenges in Utilizing Fiber-Reinforced Polymer (FRP) in Construction)

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16 pages, 2302 KiB

Open AccessArticle

Moment Redistribution in Continuous Externally CFRP Prestressed Beams with Steel and FRP Rebars

by Tiejiong Lou, Zhangxiang Li and Miao Pang

Polymers 2021, 13(8), 1181; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13081181 - 07 Apr 2021

Cited by 4 | Viewed by 1702

Abstract

This paper assesses the impact of adopting carbon- or glass-fiber-reinforced polymer (CFRP or GFRP) instead of steel rebars on the redistribution of moments in prestressed concrete beams (PCBs) with external CFRP tendons. A numerical program is introduced, and numerical simulations are performed on [...] Read more.

This paper assesses the impact of adopting carbon- or glass-fiber-reinforced polymer (CFRP or GFRP) instead of steel rebars on the redistribution of moments in prestressed concrete beams (PCBs) with external CFRP tendons. A numerical program is introduced, and numerical simulations are performed on two-span continuous beams with steel, CFRP or GFRP rebars of various areas, i.e., Ar2 = 360–3560 mm², and Ar1/Ar2 = 1.5, where Ar1 and Ar2 are areas of tensile rebars over the positive and negative moment zones, respectively. The results show the moment redistribution is contributed by concrete cracking only for the beams with fiber-reinforced polymer (FRP) rebars, and by concrete cracking and steel yielding for the beams with steel rebars. As a result, the use of FRP rebars leads to a substantially lower moment redistribution than in steel rebars. It is also demonstrated that Eurocode 2, CSA A23.3-04 and ACI 318-19 fail to reflect the rebar influence on moment redistribution in PCBs with external tendons. A simplified equation for the quantification of moment redistribution in externally PCBs with steel and FRP rebars is recommended, which yields accurate and conservative predictions. Full article

(This article belongs to the Special Issue Advances and Challenges in Utilizing Fiber-Reinforced Polymer (FRP) in Construction)

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22 pages, 9493 KiB

Open AccessArticle

Experimental Study of the Effect of High Service Temperature on the Flexural Performance of Near-Surface Mounted (NSM) Carbon Fiber-Reinforced Polymer (CFRP)-Strengthened Concrete Beams

by Younes Jahani, Marta Baena, Javier Gómez, Cristina Barris and Lluís Torres

Polymers 2021, 13(6), 920; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13060920 - 17 Mar 2021

Cited by 12 | Viewed by 2371

Abstract

This paper presents a study of the effect of high service temperature (near or beyond glass transition temperature (T_g) of structural epoxy adhesive) on the behavior of near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete (RC) beams. The study [...] Read more.

This paper presents a study of the effect of high service temperature (near or beyond glass transition temperature (T_g) of structural epoxy adhesive) on the behavior of near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP)-strengthened reinforced concrete (RC) beams. The study includes experimental work as well as analytical and numerical analysis. To this end, fourteen beams have been tested up to failure in two different series. In series 1, specimens with three different CFRP areas have been tested at two different temperatures (i.e., 20 and 40 °C). In series 2, and with the aim of evaluating the effect of higher temperatures, only one CFRP area was tested under four different temperatures (i.e., 20, 60, 70, and 85 °C). Experimental results are evaluated in terms of load–deflections, failure modes, and bond performance. Furthermore, the experimental load–deflection curves are satisfactorily compared to both analytical predictions and finite element (FE) numerical simulations. In both cases, shrinkage and temperature effects on the short-term response of flexural elements have been accounted for. No significant reduction in stiffness and ultimate load was observed for specimens being tested up to 60 °C (in the range of epoxy T_g), showing FRP rupture failure in all of them. For specimens under 70 and 85 °C, the failure mode changed from FRP rupture to FRP end debonding and concrete crushing, respectively. Full article

(This article belongs to the Special Issue Advances and Challenges in Utilizing Fiber-Reinforced Polymer (FRP) in Construction)

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16 pages, 4425 KiB

Open AccessArticle

Numerical Study of Using FRP and Steel Rebars in Simply Supported Prestressed Concrete Beams with External FRP Tendons

by Miao Pang, Zhangxiang Li and Tiejiong Lou

Polymers 2020, 12(12), 2773; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12122773 - 24 Nov 2020

Cited by 13 | Viewed by 2427

Abstract

This study aimed at examining the feasibility of using fiber-reinforced polymer (FRP) rebars instead of steel ones in prestressed concrete beams (PCBs) with external FRP tendons. By applying an experimentally validated program, numerical tests were performed on simply supported PCBs, with investigated variables [...] Read more.

This study aimed at examining the feasibility of using fiber-reinforced polymer (FRP) rebars instead of steel ones in prestressed concrete beams (PCBs) with external FRP tendons. By applying an experimentally validated program, numerical tests were performed on simply supported PCBs, with investigated variables including rebars’ type and area. Three types of rebars were considered, i.e., carbon, glass FRPs (CFRP, GFRP), and reinforcing steel. The ratio of tensile rebars ranged from 0.22% to 2.16%. The results indicated that the beams with CFRP rebars exhibited better crack mode and higher ultimate load than the beams with GFRP or steel rebars. GFRP rebars led to considerably higher ultimate deflection and tendon stress increment than steel rebars. In addition, several models for calculating the ultimate stress in unbonded tendons were assessed. An analytical model was also proposed to predict the tendon stress at ultimate and flexural strength in externally PCBs with steel and FRP rebars. The model predictions agreed well with the numerical results. Full article

(This article belongs to the Special Issue Advances and Challenges in Utilizing Fiber-Reinforced Polymer (FRP) in Construction)

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21 pages, 20742 KiB

Open AccessArticle

Flexural Properties and Microstructure Mechanisms of Renewable Coir-Fiber-Reinforced Magnesium Phosphate Cement-Based Composite Considering Curing Ages

by Liwen Zhang, Zuqian Jiang, Wenhua Zhang, Sixue Peng and Pengfei Chen

Polymers 2020, 12(11), 2556; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12112556 - 31 Oct 2020

Cited by 18 | Viewed by 2048

Abstract

As a renewable natural plant fiber, Coir fiber (CF) can be used to as an alternative to improve poor toughness and crack resistance of magnesium phosphate cement (MPC), replacing such artificial fibers as steel fiber and glass fiber and thereby reducing huge energy [...] Read more.

As a renewable natural plant fiber, Coir fiber (CF) can be used to as an alternative to improve poor toughness and crack resistance of magnesium phosphate cement (MPC), replacing such artificial fibers as steel fiber and glass fiber and thereby reducing huge energy consumptions and large costs in artificial fibers’ production and waste treatment. Aiming at examining the effects of CF volume concentrations on MPC flexural properties, this study employed a typical three-point bending test, including thirty cuboid specimens, to investigate the flexural strength, load-deflection behavior, and flexural toughness of MPC with different CF volume concentrations from 0% to 4% at the curing age of seven days and 28 days. Results demonstrated that CF presented similar effects on MPC’s properties at two curing ages. At both curing ages, as CF grew, flexural strength increased first and then decreased; specimen stiffness, i.e., MPC elastic modulus, displayed a decreasing trend; and flexural toughness was improved continuously. Additionally, modern microtesting techniques, such as, scanning electron microscopy (SEM) and energy dispersive X-ray detection (EDX), were adopted to analyze the microstructure and compositions of CF and specimens for explaining the properties microscopically. Full article

(This article belongs to the Special Issue Advances and Challenges in Utilizing Fiber-Reinforced Polymer (FRP) in Construction)

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19 pages, 5883 KiB

Open AccessArticle

Serviceability and Flexural Behavior of Concrete Beams Reinforced with Basalt Fiber-Reinforced Polymer (BFRP) Bars Exposed to Harsh Conditions

by Hakem Alkhraisha, Haya Mhanna, Noor Tello and Farid Abed

Polymers 2020, 12(9), 2110; https://0-doi-org.brum.beds.ac.uk/10.3390/polym12092110 - 16 Sep 2020

Cited by 21 | Viewed by 3112

Abstract

The main objective of this study was to investigate experimentally and numerically the behavior of basalt fiber-reinforced polymer (BFRP) reinforcement exposed to a combination of ultraviolet rays, humidity, and rain. Specifically, the effects of the previously stated harsh exposure on the serviceability performance [...] Read more.

The main objective of this study was to investigate experimentally and numerically the behavior of basalt fiber-reinforced polymer (BFRP) reinforcement exposed to a combination of ultraviolet rays, humidity, and rain. Specifically, the effects of the previously stated harsh exposure on the serviceability performance and flexural capacity of BFRP reinforced concrete beams was examined. Holding the exposure parameter constant, the study also evaluated the effects of reinforcement ratio and beam detailing on the flexural capacity and the bond-dependent coefficient (k_b) of the beams. Seven beams were cast and tested, four of which were reinforced with exposed BFRP bars, two were reinforced with unexposed BFRP bars, and one specimen was cast and reinforced with steel bars to serve as a benchmark specimen. The results indicate that the k_b factor was averaged to be 0.61 for all the beams. Test results also indicate that increasing the reinforcement ratio did not result in a directly proportional increase in the moment capacity. The period of exposure did not cause any significant impact on the behavior of the over-reinforced beams. Thus, a finite element model was created to simulate the impact of exposure on the behavior of under-reinforced BFRP reinforced concrete beams. Full article

(This article belongs to the Special Issue Advances and Challenges in Utilizing Fiber-Reinforced Polymer (FRP) in Construction)

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Review

Jump to: Research

23 pages, 2077 KiB

Open AccessReview

Durability and Mechanical Properties of Concrete Reinforced with Basalt Fiber-Reinforced Polymer (BFRP) Bars: Towards Sustainable Infrastructure

by Osama Ahmed Mohamed, Waddah Al Hawat and Mohammad Keshawarz

Polymers 2021, 13(9), 1402; https://0-doi-org.brum.beds.ac.uk/10.3390/polym13091402 - 26 Apr 2021

Cited by 22 | Viewed by 3887

Abstract

Reducing the fingerprint of infrastructure has become and is likely to continue to be at the forefront of stakeholders’ interests, including engineers and researchers. It necessary that future buildings produce minimal environmental impact during construction and remain durable for as long as practicably [...] Read more.

Reducing the fingerprint of infrastructure has become and is likely to continue to be at the forefront of stakeholders’ interests, including engineers and researchers. It necessary that future buildings produce minimal environmental impact during construction and remain durable for as long as practicably possible. The use of basalt fiber-reinforced polymer (BFRP) bars as a replacement for carbon steel is reviewed in this article by examining the literature from the past two decades with an emphasis on flexural strength, serviceability, and durability. The provisions of selected design and construction guides for flexural members are presented, compared, and discussed. The bond of BFRP bars to the surrounding concrete was reportedly superior to carbon steel when BFRP was helically wrapped and sand coated. Experimental studies confirmed that a bond coefficient k_b = 0.8, which is superior to carbon steel, may be assumed for sand-coated BFRP ribbed bars that are helically wrapped, as opposed to the conservative value of 1.4 suggested by ACI440.1R-15. Code-based models overestimate the cracking load for BFRP-reinforced beams, but they underestimate the ultimate load. Exposure to an alkaline environment at temperatures as high as 60 °C caused a limited reduction in bond strength of BFRP. The durability of BFRP bars is influenced by the type of resin and sizing used to produce the bars. Full article

(This article belongs to the Special Issue Advances and Challenges in Utilizing Fiber-Reinforced Polymer (FRP) in Construction)

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