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Thermal buckling analysis of cross-ply laminated plates using a simplified HSDT
Abdelbaki Chikh,Abdelouahed Tounsi,Habib Hebali,S. R. Mahmoud 국제구조공학회 2017 Smart Structures and Systems, An International Jou Vol.19 No.3
This work presents a simplified higher order shear deformation theory (HSDT) for thermal buckling analysis of cross-ply laminated composite plates. Unlike the existing HSDT, the present one has a new displacement field which introduces undetermined integral terms and contains only four unknowns. Governing equations are derived from the principle of the minimum total potential energy. The validity of the proposed theory is evaluated by comparing the obtained results with their counterparts reported in literature. It can be concluded that the proposed HSDT is accurate and simple in solving the thermal buckling behavior of laminated composite plates.
Simplified procedure for seismic demands assessment of structures
Benazouz Chikh,Youcef Mehani,Moussa Leblouba 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.59 No.3
Methods for the seismic demands evaluation of structures require iterative procedures. Many studies dealt with the development of different inelastic spectra with the aim to simplify the evaluation of inelastic deformations and performance of structures. Recently, the concept of inelastic spectra has been adopted in the global scheme of the Performance-Based Seismic Design (PBSD) through Capacity- Spectrum Method (CSM). For instance, the Modal Pushover Analysis (MPA) has been proved to provide accurate results for inelastic buildings to a similar degree of accuracy than the Response Spectrum Analysis (RSA) in estimating peak response for elastic buildings. In this paper, a simplified nonlinear procedure for evaluation of the seismic demand of structures is proposed with its applicability to multi-degree-of-freedom (MDOF) systems. The basic concept is to write the equation of motion of (MDOF) system into series of normal modes based on an inelastic modal decomposition in terms of ductility factor. The accuracy of the proposed procedure is verified against the Nonlinear Time History Analysis (NL-THA) results and Uncoupled Modal Response History Analysis (UMRHA) of a 9-story steel building subjected to El-Centro 1940 (N/S) as a first application. The comparison shows that the new theoretical approach is capable to provide accurate peak response with those obtained when using the NL-THA analysis. After that, a simplified nonlinear spectral analysis is proposed and illustrated by examples in order to describe inelastic response spectra and to relate it to the capacity curve (Pushover curve) by a new parameter of control, called normalized yield strength coefficient (η). In the second application, the proposed procedure is verified against the NL-THA analysis results of two buildings for 80 selected real ground motions.
CHARACTERIZATIONS OF RAPIDLY DECREASING GENERALIZED FUNCTIONS
Bouzar, Chikh,Saidi, Tayeb Korean Mathematical Society 2010 대한수학회논문집 Vol.25 No.3
The well-known characterizations of the Schwartz space of rapidly decreasing functions is extended to new algebras of rapidly decreasing generalized functions.
Abdelmounaim Mechaala,Chikh Benazouz,Hamma Zedira,Youcef Mehani,Samy Guezouli 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.2
In order to estimate the seismic demand by using the nonlinear static procedure, different approximate methods have been developed. One of the most useful methods is called displacement coefficient method (DCM), which is based on some modification factors. One of these coefficients denoted 1 C , concerns the inelastic deformation ratio and usually depends on either the yield-strength reduction factor or the ductility factor. In general the evaluation of the inelastic deformation ratio is based on the response of single degree of freedom (SDOF) systems, where the response of the structure is mainly controlled by the fundamental mode, knowing that the inelastic deformation ratio will not capture the contribution of higher modes in the overall structural response. A developed theoretical approach with the aim of estimating the inelastic deformation ratio for structures, considering contribution of higher modes of vibration, is introduced. In this assessment, the normalized yield strength coefficient (η) and the post-to-preyield stiffness ratio (α) are key factors. The results are compared to the uncoupled modal response history analysis (UMRHA) procedure and some existing formulations for a nine story building subjected to the El Centro 1940 ground motion. It appears that the new theoretical approach leads to enough accurate estimation of the inelastic deformation ratio compared to the UMRHA one.
Nonlinear thermoelastic analysis of FGM thick plates
Bouhlali, Malika,Chikh, Abdelbaki,Bouremana, Mohammed,Kaci, Abdelhakim,Bourada, Fouad,Belakhdar, Khalil,Tounsi, Abdelouahed Techno-Press 2019 Coupled systems mechanics Vol.8 No.5
In this paper, a new application of a four variable refined plate theory to analyze the nonlinear bending of functionally graded plates exposed to thermo-mechanical loadings, is presented. This recent theory is based on the assumption that the transverse displacements consist of bending and shear components in which the bending components do not contribute toward shear forces, and similarly, the shear components do not contribute toward bending moments. The derived transverse shear strains has a quadratic variation across the thickness that satisfies the zero traction boundary conditions on the top and bottom surfaces of the plate without using shear correction factors. The material properties are assumed to vary continuously through the thickness of the plate according to a power-law distribution of the volume fraction of the constituents. The solutions are achieved by minimizing the total potential energy. The non-linear strain-displacement relations in the von Karman sense are used to derive the effect of geometric non-linearity. It is concluded that the proposed theory is accurate and simple in solving the nonlinear bending behavior of functionally graded plates.
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.
Abdelkrim Rouabhia,Abdelbaki Chikh,Abdelmoumen Anis Bousahla,Fouad Bourada,Houari Heireche,Abdeldjebbar Tounsi,Kouider Halim Benrahou,Abdelouahed Tounsi,Mesfer Mohammad Al-Zahrani 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.6
The buckling properties of a single-layered graphene sheet (SLGS) are examined using nonlocal integral first shear deformation theory (FSDT) by incorporating the influence of visco-Pasternak’s medium. This model contains only four variables, which is even less than the conventional FSDT. The visco-Pasternak’s medium is introduced by considering the damping influence to the conventional foundation model which modeled by the linear Winkler’s coefficient and Pasternak’s (shear) foundation coefficient. The nanoplate under consideration is subjected to compressive in- plane edge loads per unit length. The impacts of many parameters such as scale parameter, aspect ratio, the visco-Pasternak’s coefficients, damping parameter, and mode numbers on the stability investigation of the SLGSs are examined in detail. The obtained results are compared with the corresponding available in the literature
Abdelouahed Tounsi,Abdelbaki Chikh,Houari Heireche,Mohammed Sid Ahmed Houari,E.A. Adda Bedia,Ahmed Bakora 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.57 No.4
In this work, an analytical formulation based on both hyperbolic shear deformation theory and stress function, is presented to study the nonlinear post-buckling response of symmetric functionally graded plates supported by elastic foundations and subjected to in-plane compressive, thermal and thermo-mechanical loads. Elastic properties of material are based on sigmoid power law and varying across the thickness of the plate (S-FGM). In the present formulation, Von Karman nonlinearity and initial geometrical imperfection of plate are also taken into account. By utilizing Galerkin procedure, closed-form expressions of buckling loads and post-buckling equilibrium paths for simply supported plates are obtained. The effects of different parameters such as material and geometrical characteristics, temperature, boundary conditions, foundation stiffness and imperfection on the mechanical and thermal buckling and post-buckling loading capacity of the S-FGM plates are investigated.
Ismail M. Mudhaffar,Abdelbaki Chikh,Abdelouahed Tounsi,Mohammed A. Al-Osta,Mesfer M. Al-Zahrani,Salah U. Al-Dulaijan 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.86 No.2
This work applies a four-known quasi-3D shear deformation theory to investigate the bending behavior of a functionally graded plate resting on a viscoelastic foundation and subjected to hygro-thermo-mechanical loading. The theory utilizes a hyperbolic shape function to predict the transverse shear stress, and the transverse stretching effect of the plate is considered. The principle of virtual displacement is applied to obtain the governing differential equations, and the Navier method, which comprises an exponential term, is used to obtain the solution. Novel to the current study, the impact of the viscoelastic foundation model, which includes a time-dependent viscosity parameter in addition to Winkler’s and Pasternak parameters, is carefully investigated. Numerical examples are presented to validate the theory. A parametric study is conducted to study the effect of the damping coefficient, the linear and nonlinear loadings, the power-law index, and the plate width-tothickness ratio on the plate bending response. The results show that the presence of the viscoelastic foundation causes an 18% decrease in the plate deflection and about a 10% increase in transverse shear stresses under both linear and nonlinear loading conditions. Additionally, nonlinear loading causes a one-and-a-half times increase in horizontal stresses and a nearly two-times increase in normal transverse stresses compared to linear loading. Based on the article’s findings, it can be concluded that the viscosity effect plays a significant role in the bending response of plates in hygrothermal environments. Hence it shall be considered in the design.