Natural frequencies of FGM nanoplates embedded in an elastic medium

Bouafia, Halima,Chikh, Abdelbaki,Bousahla, Abdelmoumen Anis,Bourada, Fouad,Heireche, Houari,Tounsi, Abdeldjebbar,Benrahou, Kouider Halim,Tounsi, Abdelouahed,Al-Zahrani, Mesfer Mohammad,Hussain, Muzama Techno-Press 2021 Advances in nano research Vol.11 No.3

The small scale impact on the vibrational properties of "functionally graded" (FG) nanoplate embedded in an elastic medium is examined. The formulation is based on the four-unknown refined integral plate theory on aggregate with the nonlocal elasticity theory. Contrary to other theories, this one involves only four unknown variables. The solution procedure is obtained by employing the motion differential equations of physical phase that are converted into set of "linear algebraic equations". After, these are solved by a computer code. The influences of aspect ratio, material index, nonlocal parameter and elastic medium stiffness on the different modal vibrations of FG nanoplate are explored. The results demonstrate the significant impact of different physical and geometrical parameters on the vibration behavior of FG nanoplate.

A nonlocal quasi-3D theory for bending and free flexural vibration behaviors of functionally graded nanobeams

Khadra Bouafia,Abdelhakim Kaci,Mohammed Sid Ahmed Houari,Abdelnour Benzair,Abdelouahed Tounsi 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.2

In this paper, size dependent bending and free flexural vibration behaviors of functionally graded (FG) nanobeams are investigated using a nonlocal quasi-3D theory in which both shear deformation and thickness stretching effects are introduced. The nonlocal elastic behavior is described by the differential constitutive model of Eringen, which enables the present model to become effective in the analysis and design of nanostructures. The present theory incorporates the length scale parameter (nonlocal parameter) which can capture the small scale effect, and furthermore accounts for both shear deformation and thickness stretching effects by virtue of a hyperbolic variation of all displacements through the thickness without using shear correction factor. The material properties of FG nanobeams are assumed to vary through the thickness according to a power law. The neutral surface position for such FG nanobeams is determined and the present theory based on exact neutral surface position is employed here. The governing equations are derived using the principal of minimum total potential energy. The effects of nonlocal parameter, aspect ratio and various material compositions on the static and dynamic responses of the FG nanobeam are discussed in detail. A detailed numerical study is carried out to examine the effect of material gradient index, the nonlocal parameter, the beam aspect ratio on the global response of the FG nanobeam. These findings are important in mechanical design considerations of devices that use carbon nanotubes.

Bending and free vibration characteristics of various compositions of FG plates on elastic foundation via quasi 3D HSDT model

Khadidja Bouafia,Mahmoud M. Selim,Fouad Bourada,Abdelmoumen Anis Bousahla,Mohamed Bourada,Abdeldjebbar Tounsi,E.A. Adda Bedia,Abdelouahed Tounsi 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.4

In this investigation, a novel analytical model based on combined (cubic, sinusoidal and exponential) higher order quasi-3D formulation is developed to examine flexural and free vibrational response on the various FG-plate resting on elastic foundation. The presented model is simple and contains a variable number less than others quasi-three dimensional theories. The effective properties of the structure are computed using linear, cubic, quadratic and inverse quadratic formulations which represent the volume fraction of the ceramic. The elastic foundation is structured by the constant parameter of Winkler which represents the reaction of the elastic springs and Pasternak one's in the form of a shear layer of subgrade. The analytical solution of the problem is obtained on the basis of the both Hamilton’s principle and Navier’s technique. The exactness of the current combined quasi-3D HSDT which takes into account the thickness stretching effect are checked and compared with others existing analytical models. Parametric studies are performed to shows the effects of the material distribution, inhomogeneity index, elastic foundation parameters, geometry and dimension ratios on displacements, stresses and naturel frequencies of the simply supported FG-plates.

Prediction of the Rupture of Circular Sections of Reinforced Concrete and Fiber Reinforced Concrete

Adjrad, A.,Bouafia, Y.,Kachi, M.S.,Ghazi, F. Korea Concrete Institute 2016 International Journal of Concrete Structures and M Vol.10 No.3

As part of this study, has been developed a numerical method which allows to establish abacuses connecting the normal force with bending moment for a circular section and therefore to predict the rupture of this type of section. This may be for reinforced concrete (traditional steel) or concrete reinforced with steel fibers. The numerical simulation was performed in nonlinear elasticity up to exhaustion of the bearing capacity of the section. The rupture modes considered occur by plasticization of the steel or rupture of the concrete (under compressive stresses or tensile stresses). Regarding the fiber-reinforced concrete, the rupture occurs, usually, by tearing of the fibers. The behavior laws of the different materials (concrete and steel) correspond to the real behavior. The influence of several parameters was investigated, namely; diameter of the section, concrete strength, type of steel, percentage of reinforcement and contribution of concrete in tension between two successive cracks of bending. A comparison was made with the behavior of a section considering the conventional diagrams of materials; provided by the BAEL rules. A second comparative study was performed for fibers reinforced section.

Analysis of load-settlement behaviour of shallow foundations in saturated clays based on CPT and DPT tests

Mir, Mouna,Bouafia, Ali,Rahmani, Khaled,Aouali, Nawel Techno-Press 2017 Geomechanics & engineering Vol.13 No.1

Static Penetration Test (CPT) and Dynamic Penetration Test (DPT) are commonly used in-situ tests in a routine geotechnical investigation. Besides their use for qualitative investigation (lithology, homogeneity and spatial variability), they are used as practical tools of geotechnical characterization (resistance to the penetration, soil rigidity) and modern foundation design as well. The paper aims at presenting the results of an extensive research work on the evaluation of the 1D primary consolidation settlement of saturated clayey soils on the basis of the CPT or DPT tests. The work is based on an analysis of the correlations between the tip resistance to penetration measured in these tests and the parameters of compressibility measured by the compressibility oedometer test, through a local geotechnical database in the northern Algeria. Such an analysis led to the proposal of two methods of calculation of the settlement, one based on the CPT test and the other one on the DPT. The comparison between the predicted settlements and those computed on the basis of the oedometer test showed a good agreement which demonstrate the possbility to use the CPT and DPT tests as reliable tools of computation of foundation settlements in clayey soils.

Prediction of the Rupture of Circular Sections of Reinforced Concrete and Fiber Reinforced Concrete

A. Adjrad,Y. Bouafia,M. S. Kachi,F. Ghazi 한국콘크리트학회 2016 International Journal of Concrete Structures and M Vol.10 No.3

As part of this study, has been developed a numerical method which allows to establish abacuses connecting the normal force with bending moment for a circular section and therefore to predict the rupture of this type of section. This may be for reinforced concrete (traditional steel) or concrete reinforced with steel fibers. The numerical simulation was performed in nonlinear elasticity up to exhaustion of the bearing capacity of the section. The rupture modes considered occur by plasticization of the steel or rupture of the concrete (under compressive stresses or tensile stresses). Regarding the fiber-reinforced concrete, the rupture occurs, usually, by tearing of the fibers. The behavior laws of the different materials (concrete and steel) correspond to the real behavior. The influence of several parameters was investigated, namely; diameter of the section, concrete strength, type of steel, percentage of reinforcement and contribution of concrete in tension between two successive cracks of bending. A comparison was made with the behavior of a section considering the conventional diagrams of materials; provided by the BAEL rules. A second comparative study was performed for fibers reinforced section.

Numerical Procedure for the Three-Dimensional Nonlinear Modelling of Composite Steel–Concrete Beams

Karim Benyahi,Youcef Bouafia,Marc Oudjene,Salma Barboura,Mohand Said Kachi 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.3

Composite steel–concrete structures are commonly used in the fi eld of bridges, where the steel frame provides great ease of installation, and concrete provides useful strength at low cost. This construction system makes it possible to seek to use each material to the best of its ability, so as to provide the entire construction system with greater savings. The purpose of this article is to be able to perform the simulation and the non-linear elastic calculation of composite steel–concrete beams through a calculation approach based on a matrix method of displacements. The numerical calculation model developed is based on taking into account the non-linearity of materials, or a set of laws allowing the modeling of the nonlinear behaviors of materials under an instantaneous and monotonous loading increasing until the ruin; the concrete is represented in its post-elastic part by a softening branch in compression and the contribution of the concrete stretched between two successive cracks is taken into account. Steel is represented by a perfect elastoplastic law or an elastoplastic law with fi rming. The proposed approach has been implemented on the Fortran programming language, where our procedure of numerical modeling of the mechanical behavior seems capable of correctly simulating the three-dimensional nonlinear behavior of isostatic and hyperstatic composite steel–concrete beams, under monotonous (increasing) static loading until ruin. It was validated by comparing the results of our calculations to experimental results or to analytical solutions.