Fiber Reinforced Concrete Panels Research Articles

Analytical calculation of the in-plane shear strength of fibre-reinforced concrete

Existing code prescriptions for determining the shear strength of fibre-reinforced concrete (FRC) elements are either empirical or rely on important assumptions that require further clarification. A mechanically based method is here proposed to determine the fibres and the shear reinforcement contributions to the in-plane shear strength of membrane elements. The method is derived from the comprehensive Cracked Membrane Model for FRC to determine in-plane shear strength of FRC panels and is suitably adapted to determine the shear strength of beam elements. The proposed methodology is compared to existing code formulations and validated against experimental results from 14 panels subjected to in-plane shear stresses and from 34 beams failing in shear. The average ratio between experimental and calculated shear strength is 1.00 for the panels and 1.11 for the beams, with coefficients of variation 11 % and 24 %, respectively. The proposed analytical methodology enables the determination of shear strength and failure modes in FRC elements, with or without shear reinforcement. Equations providing the fibre contribution and the compression field inclination are derived from mechanical considerations, emphasizing the key influencing variables. The proposed method can serve as a basis for code-like formulations for shear strength linked to the involved mechanics, but for which further levels of simplification are still required.

Strengthening damaged columns on the soft first story of reinforced concrete building using ultra-high-strength fiber-reinforced concrete panels

In this study, ultra-high-strength fiber-reinforced concrete (UFC) panels were used as a quick and effective measure for seismic strengthening of damaged reinforced concrete (RC) columns. Four 1/3-scale specimens, which replicated RC columns of the soft-first-story of a 10-story condominium building that was heavily damaged in the 2016 Kumamoto Earthquake, were constructed and tested. The specimens were strengthened using UFC panels after being preloaded to the drift ratio, at which the maximum load capacity of the target column was measured, and then subjected to the main loading until the ultimate state was reached. The UFC panels were installed on the two faces of the column in a direction parallel to the assumed loading direction. Two of the specimens had a UFC or RC wing wall attached to one side of the column, which was also aligned with the assumed loading direction. During the preloading and main loading, the specimens were subjected to a cyclic lateral load and varying axial load that simulated an earthquake load. The proposed method improved the maximum strength and ultimate drift ratio, and helped restore the initial stiffness of specimens with UFC panels and a wing wall to that of a column specimen during preloading. The test results of a previous study, wherein the target column, loading method, and strengthening method were the same but the specimens were not damaged before strengthening, were compared to study the impact of the damage on the RC column before strengthening.

Strengthening method by using ultra-high-strength fiber-reinforced concrete panels for a column on the soft first story of a reinforced concrete building

This paper presents a simple and efficient strengthening method by using ultra-high-strength fiber-reinforced concrete (UFC) panels on the soft first storys of reinforced concrete (RC) buildings at the risk of story collapse or shear failure of column due to earthquakes. Five 1/3 scale specimens, which replicated RC columns on the soft first story of a 10-story condominium building heavily damaged by the 2016 Kumamoto Earthquake, were constructed and tested. One of these was a reference specimen (no strengthening), and the other four were strengthened by attaching UFC panels on the two faces parallel to the assumed loading direction with or without an UFC or a RC wing wall on either column side. Cyclic lateral and varying axial loads were applied to the specimens to emulate earthquake loads. Load–deformation hysteretic responses, failure modes, and the responses of the UFC panels and the wing walls, are discussed in detail. The experimental results revealed that the reference specimen (without strengthening) had a low-load-carrying capacity and exhibited brittle shear failure, as observed in the actual building during the earthquake. Conversely, the strength and deformation capacities of the strengthened specimens improved considerably, and the effectiveness of the proposed strengthening method was validated quantitatively.

Experimental and numerical investigation of minimum required fiber content in bending characteristics of 100 MPa UHPC-formulated concrete

The present study investigates the lowest possible amount of steel and polypropylene fibers in improving the compressive and flexural strength, stiffness, and energy capacity of high strength 100 MPa concrete with a mix design similar to that of Ultra-High Performance Concrete (UHPC). Twenty-eight 100 × 200 mm cylindrical specimens with 0%, 0.2%, 0.4%, and 0.6% volumetric percentage of short steel fibers and polypropylene fibers were fabricated, which were at the lowest predicted percentages with respect to fiber content recommended in the literature. To assess the flexural performance of fiber-reinforced concrete panels, specimens with dimensions of 200 × 600 × 20 mm were made with the same steel and polypropylene fiber contents as cylindrical specimens. For each fiber percentage in flexural panels, two steel fiber and two polypropylene fiber specimens were tested under a three-point bending procedure. Results demonstrated the lowest fiber amount for compressive specimens and flexural panels. Fiber content as low as 0.2% for steel and 0.4% for PP can enhance both the strength and energy absorption capacity of the flexural panels. In addition, a formulation was proposed for estimating the concrete modulus of rupture based on experimental data. In the end, panels were modeled using ABAQUS software, and results were compared with test results. In the end, panels were modeled using ABAQUS software and results were compared with test results. The numerical predictions were in compliance with experimental observations and showed the stress distribution variations with respect to change in fiber type and percentage.

Behavior of Steel Fiber Reinforced Concrete Panels under Surface Pressure

In this study, it is aimed to investigate the importance of the affecting parameters on the pressure–displacement relationship of steel fiber reinforced concrete panels. Among these parameters, panel thickness, panel dimensions, material type, and boundary conditions of the panels are the parameters that were examined. In this context, the effects of surface pressure on the steel fiber reinforced concrete panels were investigated. It was observed that as the thickness and the fiber ratio increased, the ultimate bearing capacity increased. It was determined that it may not be enough to support the panels only at the corner points, and intermediate supports are needed. As the support spacing decreased, the absorbed surface pressure increased. In addition, it was concluded that the increase in the amount of steel fiber in the concrete material increased the strength, deflection, and ductility values.

การพัฒนาผนังคอนกรีตเสริมเส้นใยเหล็กสำหรับการต้านทานแรงกระแทกของกระสุนขนาด 7.62 x 51 มิลลิเมตร

การพัฒนาผนังคอนกรีตเสริมเส้นใยเหล็กสำหรับการต้านทานแรงกระแทกของกระสุนขนาด 7.62 x 51 มิลลิเมตร

Strengthening of Masonry Walls Produced from Two Different Materials with Steel Fiber-Reinforced Concrete Panels

The use of steel fiber-reinforced concrete panels to strengthen masonry walls is examined. Within the scope of this study, 18 of a total of 24 specimens are manufactured by using concrete panels containing steel fibers at specific ratios to strengthen hollow brick and clay brick walls, while the remainder serve as reference specimens. The shear strength, deformation and energy consumption capacities are then evaluated for each of the different strengthening methods.

Strengthening of Masonry Walls Produced from Two Different Materials with Steel Fiber-Reinforced Concrete Panels

Strengthening of Masonry Walls Produced from Two Different Materials with Steel Fiber-Reinforced Concrete Panels

Impact Resistance of Steel Fiber-Reinforced Concrete Panels Using Genetic Algorithm Optimization

Abstract In designing protective concrete structures, optimum response against projectile impact is achieved by minimizing damage and, more importantly, controlling its failure mode to ensure life safety. Recently, steel fiber–reinforced concrete (SFRC) has gained attention for its superior toughness and damage control against impact loads. However, in designing SFRC panels to protect against projectile impact, a knowledge gap exists in the selection of optimum parameters, such as steel fiber volumetric fraction, maximum aggregate size, and panel thickness. To fill this gap, this article proposes a model that is capable of predicting SFRC response to impact loading using an artificial neural network. This model has been introduced to a multiobjective genetic algorithm to optimize the SFRC panel design against a given impact energy. Simple guidelines for the selection of optimum thickness, steel fiber volumetric fraction, and aggregate size are developed.

Shear behavior of aerated concrete and hollow brick walls strengthened with steel fiber-reinforced concrete panels

Walls are the main carrying units of masonry buildings. They have certain advantages, like being economical and easily constructed. Therefore, many experimental studies have been performed. In this study, walls produced from aerated concrete (AC) and hollow brick (HB) strengthened with steel fiber-reinforced concrete panels were tested. Eighteen of 24 walls were strengthened with concrete panels that were produced by using steel fibers at certain ratios. The other six ones were reference specimens. The results obtained were expressed as mean values. The strengthening method significantly increased energy consumption capacities and shear strengths.

Strain Behavior of Concrete Panels Subjected to Different Nose Shapes of Projectile Impact.

This study evaluates the fracture properties and rear-face strain distribution of nonreinforced and hooked steel fiber-reinforced concrete panels penetrated by projectiles of three different nose shapes: sharp, hemispherical, and flat. The sharp projectile nose resulted in a deeper penetration because of the concentration of the impact force. Conversely, the flat projectile nose resulted in shallower penetrations. The penetration based on different projectile nose shapes is directly related to the impact force transmitted to the rear face. Scabbing can be more accurately predicted by the tensile strain on the rear face of concrete due to the projectile nose shape. The tensile strain on the rear face of the concrete was reduced by the hooked steel fiber reinforcement because the hooked steel fiber absorbed some of the impact stress transmitted to the rear face of the concrete. Consequently, the strain behavior on the rear face of concrete according to the projectile nose shape was confirmed.

A method for evaluating the local failure of ultra-high-performance short polyvinyl alcohol fiber-reinforced concrete panels subjected to a projectile impact

This study investigated local failure characteristics and failure limit thicknesses of an ultra-high-performance fiber-reinforced concrete panel reinforced with polyvinyl alcohol by conducting impact tests. In a series of tests, steel hemispherical projectiles with a mass of 46 g collided with ultra-high-performance fiber-reinforced concrete panels reinforced with polyvinyl alcohol. The ultra-high-performance fiber-reinforced concrete panels reinforced with polyvinyl alcohol with thicknesses in the range of 30–90 mm were tested at the impact velocities of 170–500 m/s. The experimental results revealed that the penetration depth or scabbing damage induced by the impact was significantly suppressed for the ultra-high-performance fiber-reinforced concrete panel reinforced with polyvinyl alcohol compared to that of a plain concrete panel. The experimental results demonstrated that local failure intensity for the panels was similar at equivalent impact energies, regardless of the combination of projectile mass and impact velocity. Based on the test results, we proposed a method for evaluating the penetration depth and scabbing limit thicknesses by the impact energy.

Evaluation of Impact Resistance of Steel Fiber-Reinforced Concrete Panels Using Design Equations

Evaluation of Impact Resistance of Steel Fiber-Reinforced Concrete Panels Using Design Equations

Comparative Biaxial Flexural Behavior of Ultra-High-Performance Fiber-Reinforced Concrete Panels Using Two Different Test and Placement Methods

Abstract In order to investigate the effects of fiber length, placement method, and test method on the biaxial flexural behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC), several UHPFRC panels with two different fiber lengths (Lf of 13 and 19.5 mm) were fabricated using two different placement methods (placing concrete at the center and the edge) and were then tested by two different test methods (ASTM C1550-12a and a novel biaxial flexure test (BFT)). Image analysis was also performed to quantitatively investigate the fiber distribution characteristics according to the fiber length and placement method and to thoroughly analyze the experimental results. The first cracking strength and corresponding toughness were found to be insignificantly influenced by the fiber length, placement method, and test method, but the panels with longer fibers and with concrete placed at the center (in the maximum moment region) were found to have higher biaxial flexural strength, deflection capacity, and toughness after a deflection of 2.5 mm (d2.5). The panels tested by the BFT method showed lower flexural strength, more cracks with a random distribution, and higher deviation in flexural performances than those tested by ASTM C1550. These test results were verified by evaluating the fiber distribution characteristics (i.e., the number of fibers per unit area, fiber orientation, and fiber dispersion) at localized crack surfaces by using the image analysis technique.

Shear Behavior and Crack Control Characteristics of Hybrid Steel Fiber-Reinforced Concrete Panels

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Development of an inverse analysis procedure for the characterisation of softening diagrams for FRC beams and panels

The flexural performance of fibre reinforced concrete (FRC) materials is directly related to the stress-crack opening diagram (COD). This diagram is needed for structural design applications because it represents the energy change in the fracture process zone at the material level. In this paper, a novel inverse analysis procedure for the determination of the COD for FRC standard beams (EN14651) and round panels (ASTM C1550) is presented and validated. This procedure is based on a data fitting algorithm, for which the shape of the COD is not fixed a priori (free to vary). The efficiency of this procedure is demonstrated through experimental results for the three-points notched beam and the round panel standardised FRC characterisation tests. It is worthy to mention that inverse analysis procedures for panels are, to author’s knowledge, very scarce, and this procedure can be easily extended to cover several kinds of beams and panels.

Shear strengthening of RC beams using ultra-high-strength fibre-reinforced concrete panels

This paper proposes a new shear strengthening method for reinforced concrete (RC) beams, in which ultra-high-strength fibre-reinforced concrete (UFC) panels are bonded to existing structural members, and studies the strengthening effects of the method. The experimental design and results showing the shear resisting capacity and bond-slip properties are presented. To apply the proposed strengthening method to existing RC structures, the size effect on the strengthening performance is also studied. In the experiments, two sizes of RC beams (one-quarter and half the depth of real bridge girders) are used. The proposed shear strengthening method achieves great strengthening effects on both sizes of beams and beneficial effects on shear strength and failure mode. In order to propose a proper design for the shear strengthening method, numerical methods are also used to estimate the shear force carried by UFC panels. The estimated shear force carried by the UFC panels agrees well with the experimental results.

Relationship between Fiber Orientation and Flexural Strength in Ultra-High-Performance Fiber-Reinforced Concrete Panels

In this study, the influence of fiber orientation on the flexural strength of ultra-high-performance fiber-reinforced concrete (UHPFRC) was examined. To this end, a circular UHPFRC panel measuring φ1,200 × 50 mm was cast from its center, and test specimens measuring 50 × 50 × 200 mm with 10 mm notches for three-point bending tests were cut from it with angles of 0, 30, 60 and 90° between the specimen axis and the radial direction of the panel. After the bending test, fiber orientation on the ruptured surfaces of the specimens was observed. The flexural strengths of the specimens cut at angles of 60, 30 and 0° were 80, 40 and 10% of that for the specimen cut at an angle of 90°. It was also found that the flexural strength of specimens cut from a rectangular panel cast from its center point depended on their original positions and orientation within the panel. Similar fiber orientation characteristics were found in the circular and rectangular panels.

Reinforced concrete and fiber reinforced concrete panels subjected to blast detonations and post-blast static tests

Results of an experimental study of reinforced concrete panels under blast detonations are presented. The primary purpose of the tests was to collect data for validating simulation methods for blast loads. The scaled distance ranged from 0.41m/(kg)1/3 to 0.57m/(kg)1/3 and hence the tests are close-in detonations. Four types of 1.2m square panels were subjected to blast to investigate the performance of new walls: reinforced concrete (RC) panels; fiber reinforced concrete (FRC) panels without additional reinforcement; FRC panels reinforced with steel bars; and RC panels reinforced with glass fiber reinforced polymer (GFRP) bars. Another RC panel type was built which was retrofitted with external GFRP laminates on both faces. The performance of the panels is classified into three categories as medium protection, very low protection, and protection below antiterrorism standards. FRC panels reinforced with steel bars had the best performance for new construction. Panels that survived the blast detonation without sustaining a breach were tested under monotonic static loads to determine their static post-blast load resistance.

Influence of Test Machine Control Method on Apparent Performance of ASTM C1550 Fiber Reinforced Concrete Panels

Abstract The ASTM C1550 round panel test is used to assess the post-crack performance of fiber reinforced concrete (FRC) and fiber reinforced shotcrete (FRS) and has become firmly established as the most repeatable means of post-crack performance assessment available for these materials. When the test method was first published, two methods of test machine control were permitted: displacement control, in which the displacement of the loading actuator is used as the control parameter in the test, and strain control, in which the central deflection of the specimen is used as the controlling parameter. Both these methods of control, however, require expensive testing machines, with the result that some operators have used cheaper open-loop machines to test ASTM C1550 round panels. Doubts have arisen among specifiers of FRC and FRS in tunneling and mining projects as to whether specimens tested using open-loop machines result in the same apparent performance as would be expected using displacement- or strain-controlled testing machines. This investigation has established that under certain circumstances, an open-loop testing machine can produce results for ASTM C1550 panels that are similar to results obtained using a strain- or displacement-controlled testing machine. It was also found that the measurement of specimen deflection on the underside of the panel is problematic at large deformations and can lead to substantial variations in apparent performance.