Aramid Fiber Reinforced Polymer Bars Research Articles

An Analysis of the Transfer Lengths of Different Types of Prestressed Fiber-Reinforced Polymer Reinforcement.

The main aim of this paper is to provide a broader analysis of the transfer lengths of different types of fiber-reinforced polymers (FRPs) and to provide corrections to the existing theoretical models. Therefore, this paper presents a description of the main factors that influence the transfer lengths of different types of FRPs based on experimental results found in the literature. A database of more than 300 specimens was compiled with the results of the transfer lengths of different FRPs and the main influencing parameters. The analysis of the database results showed that the transfer length of the carbon fiber composite cable (CFCC) strands depends on the type of prestressed reinforcement release. Therefore, in this article, the new coefficient αt = 2.4 is proposed for the transfer length of suddenly released CFCC strands. Additionally, the transfer length of the aramid fiber reinforced polymer (AFRP) depends on its surface conditions. Therefore, new coefficients αt = 1.5 and αt = 4.0 are also proposed for the transfer lengths of smooth braided and sanded and rough AFRP bars, respectively. Furthermore, the proposed coefficients αt = 2.6, αt = 1.9, and αt = 4.8 found in the literature were validated with the analysis of a larger database of the transfer lengths of glass fiber-reinforced polymer (GFRP) bars, carbon fiber-reinforced polymer (CFRP) bars, and gradually released CFCC strands, respectively. Moreover, the main existing theoretical models are presented, and the comparison of theoretical and experimental transfer length results is discussed. However, the low number of specimens prestressed with basalt fiber-reinforced polymer (BFRP) bars prevented the deeper analysis of the results. the analysis of the transfer length and the proposed new values of the coefficient αt provides possibilities for adapting it to design codes for engineering applications and performing additional research that fills the missing gaps in the field.

Long-term creep behavior of basalt fiber reinforced polymer bars

One of the main properties that affects the use of fiber reinforced polymer (FRP) composites in prestressing application is the long-term creep behavior. In this study the long-term creep behavior of basalt fiber reinforced polymer (BFRP) bars was investigated. The initial stress level and the fiber content presented in different diameter are the variables considered in this study. The creep rupture stress, the creep strain, and the residual properties of BFRP were experimentally studied. Moreover, the ratio of creep rupture stress after million-hour (114 years) to the initial ultimate strength of BFRP bars was extrapolated based on statistical analysis of the experimental results to be 62.3% and 57.7% for 6 and-10 mm diameters of BFRP bars, respectively. The test results showed that the creep rupture stress of BFRP bars under different sustained stresses have linear relationship with logarithm of time similar to other types of FRP bars. Additionally, the creep behavior of BFRP bars follows the three stages of creep strain similar to glass and aramid FRP bars. Moreover, based on the test results, the fiber content had proved to have a significant effect on the long-term creep behavior of BFRP bars, since the 6 mm diameter of higher fiber content exhibit lower creep strain and higher extrapolated creep rupture stress than 10 mm diameter. Finally, BFRP bars are recommended to be used in prestressing application.

Finite element modeling of reinforced concrete beams with a hybrid combination of steel and aramid reinforcement

Corrosion of steel bars has an adverse effect on the life-span of reinforced concrete (RC) members and is usually associated with crack development in RC beams. Fiber reinforced polymer (FRP) bars have been recently used to reinforce concrete members in flexure due to their high tensile strength and superior corrosion resistance properties. However, FRP materials are brittle in nature, thus RC beams reinforced with such materials would exhibit a less ductile behavior when compared to similar members reinforced with conventional steel reinforcement. Recently, researchers investigated the performance of concrete beams reinforced with a hybrid combination of steel and Aramid Fiber Reinforced Polymer (AFRP) reinforcement to maintain a reasonable level of ductility in such members. The function of the AFRP bars is to increase the load-carrying capacity, while the function of the steel bars is to ensure ductility of the flexural member upon yielding in tension. This paper presents a three-dimensional (3D) finite element (FE) model that predicted the load versus mid-span deflection response of tested RC beams conducted by other researchers with a hybrid combination of steel and AFRP bars. The developed FE models account for the constituent material nonlinearities and bond–slip behavior between the reinforcing bars and adjacent concrete surfaces. It was concluded that the developed models can accurately capture the behavior and predicts the load-carrying capacity of such RC members. In addition, a parametric study is conducted using the validated models to investigate the effect of AFRP bar size, FRP material type, bond–slip action, and concrete compressive strength on the performance of concrete beams when reinforced with a hybrid combination of steel and AFRP bars.

A Numerical Study of the Flexural Behavior of Concrete Beams Reinforced with AFRP Bars

In this study, analytical and numerical investigations were extensively conducted to evaluate the flexural behavior of concrete beams reinforced with aramid fiber-reinforced polymer (AFRP) rebars. The AFRP-reinforced concrete beams were analyzed using the separated finite element method containing different elements for concrete and reinforcement. In addition, this study used two different effective moment of inertia expressions to estimate the load-deflection responses and the service-load deflections of the beams. The service-load deflections of the AFRP-reinforced concrete beams obtained from the finite element analysis were in close agreement with those from the effective moment of inertia expressions. The numerical ultimate moments also correlated well with the analytical values of concrete stress-strain models. Numerical analyses, which hardly predict the sudden reduction in the flexural rigidity of FRP-reinforced concrete beams due to the crushing of cover concrete, were shown to provide somewhat conservative deflection estimates.

Experimental Performance of AFRP Concrete Bridge Deck Slab with Full-Depth Precast Prestressed Panels

While application of full-depth precast bridge deck panels may be appealing because of an accelerated construction schedule and improved safety conditions, corrosion of steel reinforcement is a major factor affecting the structural durability of precast panels and overall serviceability of a bridge deck. Herein, the concept of using aramid fiber reinforced polymer (AFRP) bars as a substitute for conventional steel reinforcement to overcome corrosion issues is verified. For this purpose, a full-scale bridge deck slab consisting of full-depth precast panels reinforced and prestressed with AFRP bars is constructed and experimentally evaluated in terms of load capacity, deformation, crack pattern, and failure mode. The precast panels are reinforced and prestressed in parallel and perpendicular to the traffic directions, respectively, and supported by reinforced concrete beams. Realistic dimensions, boundary conditions, and structural details are physically modeled to represent an actual bridge deck condition, and different concentrated load configurations including wheel and tandem axle loads are applied on both the slab interior span and overhang. The experimental results show the average failure load of the interior spans and overhangs, respectively equal to 3.9 and 1.4 times the maximum factored wheel load, where the deflection serviceability criteria are met and satisfactory deformability performance is achieved.

Behavior of Aramid Fiber-Reinforced Polymer Reinforced High Strength Concrete Beams under Bending

Flexural test results of ten high strength concrete beams reinforced with aramid fiber-reinforced polymer (AFRP) bars together with a steel-reinforced beam that served as a reference are presented and discussed. All beams were tested under third-point loading. Test results have shown that a concrete beam, when reinforced with AFRP bars, becomes more flexible in the postcracking range than an equivalent steel-reinforced beam, demonstrates wider and predominantly vertical cracks even in the shear span, and may fail in an unusual flexure-shear mode. Major critical issues concerning flexural designs of AFRP-reinforced beams have been discussed in the perspective of code provisions, and suitable recommendations are made for practical design. A method has been suggested to provide a meaningful quantification of ductility for FRP-reinforced beams. Also the need for reducing the maximum spacing of stirrups from that specified in the current code provisions for sections subjected to large shear combined with significant bending moment has been identified and recommendations are made.

Laboratory Evaluation and Field Application of Concrete Reinforcement with Aramid Fiber-Reinforced Polymer Bars

This research describes extensive accelerated aging tests that were conducted on polymer composite bars reinforced with aramid fibers. Aramid fiber-reinforced polymer (AFRP) bars exhibited desirable durability characteristics under a broad range of accelerated weathering effects. They also exhibited satisfactory bond strength and dowel action in concrete. A bridge deck reinforced with AFRP bars was designed with due consideration given to the punching shear mode of failure. Design procedures were verified through scaled lab tests. The construction and cost attributes of AFRPs were evaluated in this field project.