Shear strengthening of reinforced concrete beams with rectangular web openings by FRP Composites

Abdel-Kareem, Ahmed H. Techno-Press 2014 Advances in concrete construction Vol.2 No.4

This study presents the experimental results of twenty three reinforced concrete beams with rectangular web openings externally strengthened with Fiber Reinforced Polymers (FRP) composites bonded around openings. All tested beams had the same geometry and reinforcement details. At openings locations, the stirrups intercepted the openings were cut during fabrication of reinforcement cage to simulate the condition of inclusion of an opening in an existing beam. Several design parameters are considered including the opening dimensions and location in the shear zone, the wrapping configurations, and the amount and the type of the FRP composites in the vicinity of the openings. The wrapping configurations of FRP included: sheets, strips, U-shape strips, and U-shape strips with bundles of FRP strands placed at the top and sides of the beam forming a fan under the strips to achieve closed wrapping. The effect of these parameters on the failure modes, the ultimate load, and the beam stiffness were investigated. The shear contribution of FRP on the shear capacity of tested beams with web openings was estimated according to ACI Committee 440-08, Canadian Standards S6-06, and Khalifa et al. model and examined against the test results. A modification factor to account for the dimensions of opening chords was applied to the predicted gain in the shear capacity according to ACI 440-08 and CSA S6-06 for bonded Glass Fiber Reinforced Polymers (GFRP) around openings. The analytical results after incorporating the modification factor into the codes guidelines showed good agreement with the test results.

Shear strengthening of reinforced concrete beams using NSM/EBR techniques

Abdel-kareem, Ahmed H.,Debaiky, Ahmed S.,Makhlouf, Mohamed H.,Abdel-baset, M. Techno-Press 2021 Advances in concrete construction Vol.12 No.1

This paper presents the experimental results of research into the behavior of shear-enhanced reinforced concrete R.C beams using steel stirrups, Fiber Reinforced Polymers FRP rods, and Fiber Reinforced Polymers FRP strips. This enhancement was accomplished by the Near Surface Mounted technique NSM. The NSM technique contains a groove on the outside surface of the concrete member to adjust the depth to be less than the cover of the member. After cleaning, the epoxy paste was used to fill half of the groove's depth. In the groove, the particular FRP element is then installed. Finally, the groove is filled with epoxy and the outside surface of the concrete is levelled with so much epoxy. This method enables the fiber reinforcement polymer FRP materials is covered completely by epoxy. The objective of this research is to study the effect of NSM technique on shear resistance for stressed beam. 13 experimental studies of half-scale R.C beams were involved in this paper. The experimental program included two specimens strengthened with steel stirrups, eight specimens strengthened with stirrups of Glass Fiber Reinforced Polymer GFRP rods with the shape of deferent end anchorage and angle, two specimens strengthened with externally bonded GFRP strips. The remaining un-strengthened specimen was allocated for comparison as a control one. The test results included ultimate load of capacity, deflection, cracking, and failure mode. All beams enhanced with GFRP rods showed a capacity improvement ranging from 14% to 85% compared to the reference beam, and compared to the reference beam, beams enhanced with GFRP strips showed a capacity improvement ranging from 7% to 22%.

Study of the characteristics of forced homogeneous turbulence using band-pass Fourier filtering

Waleed Abdel Kareem 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.3

Simulations of forced homogeneous isotropic turbulence with resolutions of 1283 and 2563 using the Lattice Boltzmann method are carried out. The multi-scale vortical structures are identified using the band-pass Fourier cutoff filtering. Three fields at each simulation are extracted and their characteristics are studied. The vortical structures are visualized using the Q-identification method. A new lattice segmentation scheme to identify the central axes of the vortical structures is introduced. The central points of each vortex are identified and they are connected using the direction cosines technique. Results show that the Q-spectrum of the fine scale field survives at low and high wave-numbers. However, the large and intermediate Q-spectra survives till wave-numbers less than or equal to twice the used velocity cutoff wave-numbers. It is found that the extracted central axes clearly resemble the corresponding vortical structures at each scale. Using the central axes scheme, the radii and lengths of the vortical structures at each scale are determined and compared. It is also found that the radii of the identified vortical structures at each scale in both simulations are of the order of several times the Kolmogorov microscales.

Bending analysis of the multi-phase nanocomposite reinforced circular plate via 3D-elasticity theory

Feng Shao,Yanshang Wang,Abdel Kareem Alzo’ubi,Mamdooh Alwetaishi,Mohamed Amine Khadimallah 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.4

In this article bending response of multi-phase nanocomposite (MPC) filled by circular plates (MPCCP) in the framework of the three-dimensional elasticity model under bi-directional initially stressed (BDIS) resting on non-polynomial elastic foundation for a broad range of boundary conditions is presented. The discrete singular convolution (SS-DSC) based on state-space is provided to evaluate the bending characteristics of MPCCP by considering various boundary conditions. Halpin– Tsai model and micro-scaled fibers have been applied in the hierarchy to anticipate the properties of bulk material of the multiscaled composites. In order to model a disk, singular point has been analyzed. The graphene platelets (GPLs) are assumed to be oriented in random directions and distributed in uniform pattern in the epoxy resin matrix. Then, to provide the influences of primary stressed, elastic substrate and a range of pressure types on the bending behavior of the MPCCP, a parametric analysis has been conducted. Computational outcomes disclose that sinusoidal load is the best pressure for improving the deformation resistances and stress of the nanocomposite circular/annular plates.

On the numerical solutions of integral equation of mixed type

Mohamed A. Abdou,Khamis I. Mohamed,Abdel-Kareem S. Ismail 한국전산응용수학회 2003 Journal of applied mathematics & informatics Vol.12 No.1-2

Protective effect of vitamin C against ivermectin induced nephrotoxicity in different age groups of male wistar rats: bio-histopathological study

Shereen E. Tawfeek,Ayat M. Domouky,Reham H. Abdel-Kareem 대한해부학회 2021 Anatomy & Cell Biology Vol.54 No.4

Ivermectin (Ive) has exceedingly efficient against several microorganisms including viruses; therefore, it could help as a potential treatment of COVID-19. Because of increasing consumption of ivermectin and vitamin C (Vit.C) in hope to treat COVID-19, and because of ivermectin nephrotoxic effects have not been fully clarified especially in juvenile age, it was conducted to examine the histopathological and biochemical effects of ivermectin on adult and juvenile kidneys, and to assess the possible protective role of Vit.C against this potential toxicity. Rats were divided to 4 subgroups (Control subgroup, Vit.C subgroup, Ive subgroup, and Vit.C+Ive subgroup), 1 week after 4 doses of ivermectin (0.4 mg/kg Ive±1.25 mg/kg Vit.C), blood samples obtained for assessment of kidney function test, part of kidneys prepared for determination of matrix metalloproteinase-9 and antioxidant enzymes essay. Other parts prepared for histopathological and ultrastructural examination. Results showed that administration of ivermectin led to attenuation in kidney function and in activities of the antioxidant enzymes and increase in matrix metalloproteinase-9 activity. In addition, there were histological damages (shrunken glomeruli, widened urinary space, cytoplasmic vacuolation and pyknotic nuclei with epithelial exfoliation, extravasated blood, and mononuclear cell infiltration) and immunohistochemistry revealed increase in percentage of Bax proapoptotic protein expression. Also, ultrastructure examination showed alteration in cell architecture. All these changes were more obvious in juvenile group while co-administration of Vit.C led to significant protection more in adult group. In conclusion, Ivermectin should be used cautiously especially in juvenile age, and co-administration of Vit.C is highly recommended.