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Dynamic characteristics of viscoelastic nanobeams including cutouts
Rabab A. Shanab,Norhan A. Mohamed,Mohamed A. Eltaher,Alaa A. Abdelrahman Techno-Press 2023 Advances in nano research Vol.14 No.1
This paper aimed to investigate the nonclassical size dependent free vibration behavior of regularly squared cutout viscoelastic nanobeams. The nonlocal strain gradient elasticity theory is modified and adopted to incorporate the viscoelasticity effect. The Kelvin Voigt viscoelastic model is adopted to model the linear viscoelastic constitutive response. To explore the influence of shear deformation effect due to cutout, both Euler Bernoulli and Timoshenko beams theories are considered. The Hamilton principle is utilized to derive the dynamic equations of motion incorporating viscoelasticity and size dependent effects. Closed form solutions for the resonant frequencies for both perforated Euler Bernoulli nanobeams (PEBNB) and perforated Timoshenko nanobeams (PTNB) are derived considering different boundary conditions. The developed procedure is verified by comparing the obtained results with the available results in the literature. Parametric studies are conducted to show the influence of the material damping, the perforation, the material and the geometrical parameters as well as the boundary and loading conditions on the dynamic behavior of viscoelastic perforated nanobeams. The proposed procedure and the obtained results are supportive in the analysis and design of perforated viscoelastic NEMS structures.
Buckling of 2D FG Porous unified shear plates resting on elastic foundation based on neutral axis
Rabab Shanab,Salwa Mohamed,Mohammed Y. Tharwan,Amr E. Assie,Mohamed A Eltaher 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.45 No.5
The critical buckling loads and buckling modes of bi-directional functionally graded porous unified higher order shear plate with elastic foundation are investigated. A mathematical model based on neutral axis rather than midplane is developed in comprehensive way for the first time in this article. The material constituents form ceramic and metal are graded through thickness and axial direction by the power function distribution. The voids and cavities inside the material are proposed by three different porosity models through the thickness of plate. The constitutive parameters and force resultants are evaluated relative to the neutral axis. Unified higher order shear plate theories are used to satisfy the zero-shear strain/stress at the top and bottom surfaces. The governing equilibrium equations of bi-directional functionally graded porous unified plate (BDFGPUP) are derived by Hamilton’s principle. The equilibrium equations in the form of coupled variable coefficients partial differential equations is solved by using numerical differential integral quadrature method (DIQM). The validation of the present model is presented and compared with previous works for bucking. Deviation in buckling loads for both mid-plane and neutral plane are developed and discussed. The numerical results prove that the shear functions, distribution indices, boundary conditions, elastic foundation and porosity type have significant influence on buckling stability of BDFGPUP. The current mathematical model may be used in design and analysis of BDFGPU used in nuclear, mechanical, aerospace, and naval application.
Effect of Adding Zeolitic Tuff on Geotechnical Properties of Lime-Stabilized Expansive Soil
Samer R. Rabab'ah,Madhar M. Taamneh,Hussein M. Abdallah,Osama K. Nusier,Laith Ibdah 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.12
This study aims to evaluate experimentally the potential of expansive soil stabilization using different additives: zeolitic tuff (ZT), lime, and a combination of lime and ZT. Four different percentages of ZT (10%, 20%, 25%, and 30%), three percentages of lime (2%, 4%, and 6%), and variable percentages of their combinations were used to stabilize the soil for pavement subbase application. Atterberg limits, pH, compaction, linear shrinkage, swelling, unconfined compressive strength (UCS), and California bearing ratio (CBR) tests were performed on treated and untreated soil specimens at different curing times. Results showed that ZT additives effectively reduced the plasticity, linear shrinkage, and swell potential in addition to increase the maximum dry unit weight, UCS, and CBR. The results of this study were supported by a microstructural analysis using scanning electron microscopy (SEM) associated with the energy-dispersive X-ray spectroscopy (SEM/EDX) technique. It was determined that the UCS and CBR values for the 4% lime stabilized soil increased by 22% and 70%, respectively, after the addition of 25% ZT. Based on evaluation of the results, an optimum mixture of 25% ZT and 4% lime stabilized soil can be used in pavement subbase applications as it achieved the minimum strength target.
Mehrbakhsh Nilashi,Rabab Ali Abumalloh,Ahmed Almulihi,Mesfer Alrizq,Abdullah Alghamdi,Muhammed Yousoof Ismail,Abul Bashar,Waleed Abdu Zogaan,Shahla Asadi 한국통신학회 2023 ICT Express Vol.9 No.2
Revealing customer satisfaction through big social data has been an interesting research topic in tourism and hospitality. Big data analysis is an effective way to detect customers’ behaviors in their decision-making. This study aims to perform big social data analysis to reveal whether food quality impacts the relationship between hotel performance criteria and travelers’ satisfaction. A two-stage methodology is developed to address the objectives of this study. The findings demonstrated that there is a positive relationship between eco-friendly hotels’ performance criteria and satisfaction. The results and implications for managers and future research directions are discussed.
Ola A. Siam,Rabab A. Shanab,Mohamed A. Eltaher,Norhan A. Mohamed Techno-Press 2023 Advances in aircraft and spacecraft science Vol.10 No.3
This manuscript is dedicated to deriving the closed form solutions of free vibration of viscoelastic nanobeam embedded in an elastic medium using nonlocal differential Eringen elasticity theory that not considered before. The kinematic displacements of Euler-Bernoulli and Timoshenko theories are developed to consider the thin nanobeam structure (i.e., zero shear strain/stress) and moderated thick nanobeam (with constant shear strain/stress). To consider the internal damping viscoelastic effect of the structure, Kelvin/Voigt constitutive relation is proposed. The perforation geometry is intended by uniform symmetric squared holes arranged array with equal space. The partial differential equations of motion and boundary conditions of viscoelastic perforated nonlocal nanobeam with elastic foundation are derived by Hamilton principle. Closed form solutions of damped and natural frequencies are evaluated explicitly and verified with prestigious studies. Parametric studies are performed to signify the impact of elastic foundation parameters, viscoelastic coefficients, nanoscale, supporting boundary conditions, and perforation geometry on the dynamic behavior. The closed form solutions can be implemented in the analysis of viscoelastic NEMS/MEMS with perforations and embedded in elastic medium.
Alaa A. Abdelrahman,Rabab A. Shanab,Ismail Esen,Mohamed A Eltaher 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.2
This manuscript illustrates the dynamic response of nanoscale carbon nanotubes (CNTs) embedded in an elastic media under moving load using doublet mechanics theory, which not considered before. CNTs are modelled by Timoshenko beam theory (TBT) and a bottom to up modelling nano-mechanics is simulated by doublet mechanics theory to capture the size effect of CNTs. To explore the influence of the CNTs configurations on the dynamic behaviour, both armchair and zigzag configurations are considered. The governing equations of motion and the associated boundary conditions are obtained using the Hamiltonian principle. The Navier solution methodology is applied to obtain the solutions for both orientations. Free vibration and forced response under moving loads are considered. The accuracy of the developed procedure is verified by comparing the obtained results with available previous algorithms and good agreement is observed. Parametric studies are conducted to demonstrate effects of doublet length scale, CNTs configurations, moving load velocities as well as the elastic media parameters on the dynamic behaviours of CNTs. The developed procedure is supportive in the design and manufacturing of MEMS/NEMS made from CNTs.
Awni Abu-Shamah,Rabab Allouzi 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.5
Recently, Concrete-filled double skin steel tubular (CFDST) columns have proven an exceptional structural resistance in terms of strength, stiffness, and ductility. However, the resistance of these column members can be severely affected by the type of loading in which bending stresses increase in direct proportion with axial load and eccentricity value. This paper presents a non-linear finite element based modeling approach that studies the behavior of slender CFDST columns under biaxial loading. Finite element models were calibrated based on the outcomes of experimental work done by other researchers. Results from simulations of slender CFDST columns under axial loading eccentric in one direction showed good agreement with the experimental response. The calibrated models are expanded to a total of thirty models that studies the behavior of slender CFDST columns under combined compression and biaxial bending. The influences of parameters that are usually found in practice are taken into consideration in this paper, namely, eccentricity-to-diameter (e/D) ratios, slenderness ratios, diameter-to-thickness (D/t) ratios, and steel contribution ratios. Finally, an analytical study based on current code provisions is conducted. It is concluded that South African national standards (2011) provided the most accurate results contrasted with the Eurocode 4 (2004) and American Institute of Steel Construction (2016) that are found to be conservative. Accordingly, correction factors are proposed to the current design guidelines to provide more satisfactory results.