Browsing by Author "El-said, Amr"

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Crack sliding model for non-shear FRP-reinforced slender concrete elements under shear
(Frontiers Media S.A., 2023-03) El-said, Amr; Awad, Ahmed; El-Sayed, Taha A; Özkılıç, Yasin Onuralp; Deifalla, A; Tawfik, Maged
Fiber-reinforced polymer (FRP)-reinforced concrete (RC) elements fail under one-way shear in a devastating and complicated manner with no adequate warning. In recent decades, there has been pioneering research in this area; however, there is no agreement among researchers regarding mechanicallybased models. Thus, in this current study, a plasticity-based model is developed for FRP-RC elements under shear. A selected model was firstly assessed for its accuracy, consistency, and safety against an extensive experimental database. Secondly, a plasticity-based model (i.e., crack shear sliding model) was adapted, refined, and proposed for FRP-RC elements under one-way shear. The two proposed models were found to be reliable and more accurate with respect to selected existing methods. Modeling of FRP’s axial rigidity is more consistent only under Young’s modulus with respect to the experimental database. Several concluding remarks on the selected existing models are outlined and discussed to assist the future development of these models and design codes.
Effect of hybrid-fiber- reinforcement on the shear behavior of high-strength-concrete beams
(Frontiers Media S.A., 2023-01) Awad, Ahmed; Tawfik, Maged; Deifalla, A.; Ahmad, Mahmood; Sabri, Mohanad Muayad Sabri; El-said, Amr
The shear behavior of concrete beams is highly affected by the implementation of better performance concrete. Hybrid fibers addition to concrete mixture has proven to improve the performance compared to just using single type of fiber. Thus, in this current study, the shear behavior of hybrid-fiber-reinforced-high-strength- concrete beams was investigated experimentally. In addition, the effect of the span-to-depth ratio and the transverse reinforcement ratio were examined. Results showed that, when .45% of the cement weight is replaced with polypropylene fiber and 7% of the cement weight is replaced with steel fibers, the shear strength of the beam was enhanced by 18% in comparison to the control beam. The Formation and progression of cracks were also better controlled. The behavior of hybrid-polypropylene-steel-fibers-high-strength-concrete beams was observed to be comparable to that of conventional concrete ones as the shear strength increased with the decrease in span to depth ratio or the increase in transverse reinforcing ratio. A non-linear numerical model was developed and validated using the experimental results. The shear capacities of beams were calculated using ACI, which was compared to experimental and numerical results. The ACI’s calculations were conservative when compared with the experimental or numerical results. The coefficient of variance between the ACI and experimental shear capacity results was 4.8%, while it was 9.2% between the ACI and numerical shear capacity results.
The Mechanical Behavior of Sustainable Concrete Using Raw and Processed Sugarcane Bagasse Ash
(MDPI AG, 2022-09) El-said, Amr; Awad, Ahmed; Ahmad, Mahmood; Sabri, Mohanad Muayad Sabri; Deifalla, Ahmed Farouk; Tawfik, Maged
Sugarcane Bagasse Ash (SCBA) is one of the most common types of agricultural waste. By its availability and pozzolanic properties, sugarcane bagasse ash can be utilized as a partial replacement for cement in the production of sustainable concrete. This study experimentally investigated the impact of employing two types of sugarcane bagasse ash as a partial substitute for cement up to 30% on the compressive strength, flexural strength, and Young’s modulus of the concrete mixture. The first type of bagasse ash used was raw SCBA, which was used as it arrived from the plant, with the same characteristics, considering that it was exposed to a temperature of 600 ◦C in the boilers to generate energy. The second type of bagasse ash utilized, called processed SCBA, was produced by regrinding raw SCBA for an hour and then burning it again for two hours at a temperature of 600 ◦C. This was done to improve the pozzolanic activity and consequently the mechanical properties of the concrete mixture. The findings indicated that employing raw sugarcane bagasse ash had a detrimental effect on the mechanical characteristics of the concrete mixture but using processed sugarcane bagasse ash at a proportion of no more than 10% had a considerable effect on improving the properties of the concrete mixture. The utilization of processed SCBA up to 10% into the concrete mixture resulted in a 12%, 8%, and 8% increase in compressive strength, flexural strength, and Young’s modulus, respectively, compared to the normal concrete specimen. On the contrary, the inclusion of raw SCBA with varying content into the concrete mixture decreased compressive strength, flexural strength, and Young’s modulus by up to 50%, 30%, and 29%, respectively, compared to the normal concrete specimen. The experimental findings were validated by comparison with ACI predictions. ACI overestimated the flexural strength of SCBA concrete specimens, with a mean coefficient of difference between the ACI equation and experimental results of 22%, however, ACI underestimated the Young’s modulus of SCBA concrete specimens, with a mean coefficient of difference between the ACI equation and experimental results of −6%.
Mechanical Properties of Hybrid Steel-Polypropylene Fiber Reinforced High Strength Concrete Exposed to Various Temperatures
(Multidisciplinary Digital Publishing Institute (MDPI), 2022-06-12) Tawfik, Maged; El-said, Amr; Deifalla, Ahmed; Awad, Ahmed
Combining different types of fibers inside a concrete mixture was revealed to improve the strength properties of cementitious matrices by monitoring crack initiation and propagation. The contribution of hybrid fibers needs to be thoroughly investigated, taking into consideration a variety of parameters such as fibers type and content. In this paper, the impact of integrating hybrid steel-polypropylene fibers on the mechanical properties of the concrete mixture was investigated. Hybrid fiber-reinforced high-strength concrete mixtures were tested for compressive strength, tensile strength, and flexural strength. According to the results of the experiments, the addition of hybrid fibers to the concrete mixture improved the mechanical properties significantly, more than adding just one type of fiber for specimens exposed to room temperature. Using hybrid fibers in the concrete mixture increased compressive, tensile, and flexural strength by approximately 50%, 53%, and 46%, respectively, over just using one type of fiber. Furthermore, results showed that including hybrid fibers into the concrete mixture increased residual compressive strength for specimens exposed to high temperatures. When exposed to temperatures of 200 ◦C, 400 ◦C, and 600 ◦C, the hybrid fiber reinforced concrete specimens maintained 87%, 65%, and 42% of their initial compressive strength, respectively. In comparison, the control specimens, which were devoid of fibers, would be unable to tolerate temperatures beyond 200 ◦C, and an explosive thermal spalling occurred during the heating process.