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RISS 인기검색어
- 검색키워드
- 저자 : Ehsanollah Zeighami (검색결과 3 건)
- 무료
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Maryam Ashouri,Ehsanollah Zeighami,Alireza Azarioon,Seyyed Mohammad Mirhosseini,Sattar Ebrahimi Yonesi Techno-Press 2024 Advances in nano research Vol.16 No.5
Microscopic defects within the microstructure of hardened cement paste are the main source of weakness in concrete. As a solution, nano-graphene oxide (GO) can be employed to improve the cement paste microstructure. However, there is a number of disadvantages, e.g., fluidity reduction and non-uniform dispersion. The present study sought to modify GO by fabricating a copolymer (PSGO) in a novel process to exploit the advantages of nano-GO while minimizing its disadvantages. Using 0.03wt% copolymerled to 38.8% higher tensile strength, 29.3% higher compressive strength and 25% higher workability. The SEM images revealed that GO and modified GO enhanced concrete by secondary hydration and bonding with C-S-H, creating a firm, integrated, and foil-like structure, and reducing the crack size and depth.
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Mojtaba Shokri,Mahmoud Edalati,S. Mohammad Mirhosseini,Ehsanollah Zeighami 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.5
Although torsion is usually considered a secondary consideration in structural design, it can lead to failures, especially in structures with irregular geometry exposed to seismic forces or in unique situations. While some studies have explored the size effect on the torsional behavior of RC beams, none have addressed the impact of reinforcement. This paper investigates the size effect on the torsional behavior of RC beams with varying reinforcement ratios, including both FRP sheets and steel rebars. In this study, the torsional behavior of reinforced concrete (RC) beams with and without FRP strengthening was investigated numerically. Modeling was carried out by Finite element (FE) software ABAQUS and validated using experimental data from literature. The torsional behavior of 24 models with differences in cross-section size and reinforcement ratio were investigated. Concrete damage plasticity, Hashin damage criteria, and von Mises stress were used to investigate the damage in concrete, FRP, and steel, respectively. The cracking torsional moment, ultimate torsional moment, and torque-twist curve of the beams were evaluated and presented. The results indicated the presence of a significant size effect in the torsional strength of beams. After reinforcing the beams with FRP fabrics, the average cracking moment increased by a range of 1.72% to 36% across different groups of beams. An 8.2% increase in ultimate strength is observed with just a 0.4% rise in the FRP strengthening ratio. Post-cracking behavior was seen in 8 models with adequate steel and FRP reinforcement ratio.
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Comparison of Hydraulic Performance of Triangular Side Weirs with a Focus on the Overhang Type
Maryam Yeganeh,Mohammadreza Jalili Ghazizadeh,Mojtaba Saneie,Ehsanollah Zeighami 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.10
This paper has studied the performance of different triangular labyrinth side weirs. To evaluate the effectiveness of the various schemes: triangulating, adding sloped floors to the cycles, apex overhanging, and changing to an asymmetry plan were experimentally investigated. Continuous improvement has been achieved in these examinations. The average increase of the discharge coefficients relative to the rectangular side weirs was 80, 82, 87, and 96% for triangular side weirs, triangular side weirs with sloped floors, triangular side weirs with sloped floors and overhangs, and asymmetric triangular side weirs with sloped floors and overhangs, respectively. Velocity components near side weirs also confirmed higher performance for the asymmetric plan. Two new equations have been presented to estimate the discharge coefficient of the two-cycle triangular side weirs and triangular side weirs with sloped floors and overhangs. The proposed equation for the triangular side weirs was supported by the present laboratory data, as well as data from other researchers covering different apex angles of 35°, 45°, 60°, 90°, 120°, and 140°. The study results can be used to design triangular side weirs for enhancing the discharge capacity where the channel bank is limited to pass the required flow rate.
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