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In this research, the structural behavior of reinforced concrete brackets cast with concrete containing different types of fibers was studied. Seven samples of reinforced concrete corbels were cast and tested. One specimen was cast without fiber as a reference, and the other samples were made with six different types of fibers at a constant volume...
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... along the column-corbel interface, tension tie yielding, compression strut crushing or splitting, and localized bearing or shearing failure under the loading plate are all possible failure modes for corbel. A corbel is a shear-critical structure and is dominated by disturbed regions (D-regions), as shown in Figure 1. ACI 318-19 [1] provides a typical steel reinforcement distribution (Figure 2) for resisting the customary disturbed stress distribution that is compatible with the strut-tie model ( Figure 3). ...
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... the applied load increases, the inclined cracks propagate, leading to a new sudden inclined cracks formation. The principal diagonal shear crack grows increasingly wider as the corbel fails, and in all specimens, this crack separate between the supports and the column-corbel intersection at the inclined face, break one of the double corbels from the withstanding column, as seen in Figure 10. All the corbels fail with the same pattern, but the corbels with fibers are more ductile than the control corbel Table 8 shows incline cracking and ultimate loads. ...
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... the tested corbels fail in inclined shear; the comparison is performed with the first cracking load for the control C1, fiber-reinforced concrete corbels made with steel fibers of different lengths and shapes C2, C3, C4, C5 and C6 , furthermore, corbel made with concrete containing polyolefin fiber C7. Figure 11 demonstrates the load-deflection curves for the tested RC corbels. The load-deflection curve can be divided into two stages, the first of which appears to be a straight line and begins at the initial points and ends at the developed crack, representing the linear behavior of the tested specimens. ...
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... second segment is usually represented by a curve that depicts the nonlinear behavior of the concrete corbels and runs from the developed first visible crack to the final failure stage. From Figure 11, it is clear that the addition of fiber to concrete increases the stiffness in the elastic stage and the ductility in the plastic stage. Additionally, it can be innovated that the corbel, which contains steel fibers sizes 50 mm and 60 mm in length exhibits high stiffness in the pre-cracking phase and after cracking. ...
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In this study, the performance of short fibers to improve resistance against shear loading is evaluated. The hook-end steel fiber with length of 50 mm (aspect ratio of 67) and the 30-mm long straight aramid fiber with the aspect ratio of 50 was tested and compared. The splitting tensile strength and ductility of concrete was substantially improved...
Citations
... Research shows that an effective method to improve the performance of concrete is the addition of fiber materials into concrete [10][11][12][13], such as glass fiber [14], polypropylene fiber [15], carbon fiber [16], and steel fiber [17]. Limited by cost performance and fiber properties [18,19], some kinds of fibers are difficult to use widely in the large-scale production its performance met the requirements of Chinese standard JGJ/T283-2012. ...
The mechanical properties and impact resistance of conventional self-compacting concrete (SCC) need to be further improved. In order to explore the dynamic and static mechanical properties of copper-plated steel-fiber-reinforced self-compacting concrete (CPSFRSCC), the static mechanical properties and dynamic mechanical properties of CPSFRSCC with a different volume fraction of copper-plated steel fiber (CPSF) are tested, and a numerical experiment is carried out to analyze the experimental results. The results show that the mechanical properties of self-compacting concrete (SCC) can be effectively improved by adding CPSF, especially for the tensile mechanical properties. The static tensile strength of CPSFRSCC shows a trend that increases with the increase in the volume fraction of CPSF and then reaches the maximum when the volume fraction of CPSF is 3%. The dynamic tensile strength of CPSFRSCC shows a trend that increases first and then decrease with the increase in the volume fraction of CPSF, and then reaches the maximum when the volume fraction of CPSF is 2%. The results of the numerical simulation show that the failure morphology of CPSFRSCC is closely related to the content of CPSF; with the increase in the volume fraction of CPSF, the fracture morphology of the specimen gradually evolves from complete fracture to incomplete fracture.
... Moreover, results showed that the use of SFR affect the load-carrying capacity and ductility of RC corbels both before and after exposure to elevated temperatures (Abdulhaleem et al. 2018). It was also revealed that steel and polyolefin fiber can improve the cracking loads, and the shape of the steel fiber clearly affects the ultimate load (Saleh et al. 2022). Using fiber-reinforced polymer (FRP) systems for strengthening has received a lot of attention from researchers in the last decade. ...
Reinforced concrete corbels in precast structures are the most popular type of connection between beams and columns. Nonetheless, corbels collapse in most cases in a catastrophic and sudden way due to a variety of factors. Despite the fact that numerous studies have been conducted to strengthen the damaged concrete elements with external reinforcement techniques, there are only a few studies have been conducted specifically to investigate the effects of external reinforcement by fiber-reinforced polymer on the shear response. The present paper aims to simulate the nonlinear structural behavior of reinforced concrete corbels externally strengthened with carbon fiber-reinforced polymer strips. Therefore, a case study of corbel was chosen in order to elaborate a several three-dimensional finite element models by varying in amount, direction, and thickness of the carbon strips. The reliability of the numerical models was validated by comparing the numerical results to the data of experimental campaign of previous published studies. The validated model was then used in a parametric study to investigate the major parameters that significantly influence corbel behavior, such as the influence of the compressive strength of concrete and the effect of the secondary reinforcements. The results showed that the diagonal reinforcement limited shear crack propagation and widening, resulting in a gain in load capacity of up to 66%. In addition, the increase of the ratio of shear span-to-effective depth a/d from 0.5 to 1.0 decreased load capacity by up to 40%, which confirmed that the corbel strength is much affected by increasing span–depth ratio. Moreover, the thickness of the carbon strips has more effect on the ultimate load, ductility, and toughness of the corbels, especially in inclined configuration resulting in an increase in shear capacity up to 123%. The increase in the compressive strength of concrete leads to improve the shear capacity by up to 57%. Furthermore, the incorporation of horizontal secondary reinforcement contributed along the depth of the corbels to an additional strength gain of up to 16%. The numerical behavior results are rather well-matched to those found experimentally in the term of load–deflection curves.
In this research, five experimental samples of reinforced concrete moment-resisting frames were constructed and tested. The first sample has been tested as a control sample, two samples had polypropylene and metal fibers. In the next two samples, a deliberate manufacturing error was created by using air-entraining admixture materials at the connection of the beam and the column, in order to check the effect of the additive fibers on the frames with manufacturing errors. The parameters of ultimate strength, stiffness ductility, energy dissipation capacity, and strength reduction factor were evaluated. The results showed that the use of additive fibers improves the overall performance of the frame. It was also concluded that if these additive fibers are used, the effect of manufacturing error on the moment-resisting reinforced concrete frames will be resolved to a great extent. The results show that all seismic parameters increase significantly if the optimal ratio of fibers is used in concrete material. Improving the performance of experimental frames in the presence of porosity in connections with additive fibers was also studied. It can be said that the use of fibers has been able to increase the ultimate strength, stiffness, ductility, and strength reduction factor in samples with porosity in the range of the control sample. However, the capacity of energy dissipation in these samples has suffered a noticeable drop. In the end, the numerical models were made in ABAQUS software to verify the validity of the experiments and compared with the results of the experimental models.
