Abstract
Two-directional functionally graded materials (2D-FGMs) show extraordinary physical properties which makes
them ideal candidates for designing smart micro-switches. Pull-in instability is one of the most critical challenges in the design
of electrostatically-actuated microswitches. The present research aims to bridge the gap in the static pull-in instability analysis of
microswitches composed of 2D-FGM. Euler-Bernoulli beam theory with geometrical nonlinearity effect (i.e. von-Karman
nonlinearity) in conjunction with the modified couple stress theory (MCST) are employed for mathematical formulation. The
micro-switch is subjected to electrostatic actuation with fringing field effect and Casimir force. Hamilton's principle is utilized to
derive the governing equations of the system and corresponding boundary conditions. Due to the extreme nonlinear coupling of
the governing equations and boundary conditions as well as the existence of terms with variable coefficients, it was difficult to
solve the obtained equations analytically. Therefore, differential quadrature method (DQM) is hired to discretize the obtained
nonlinear coupled equations and non-classical boundary conditions. The result is a system of nonlinear coupled algebraic
equations, which are solved via Newton-Raphson method. A parametric study is then implemented for clamped-clamped and
cantilever switches to explore the static pull-in response of the system. The influences of the FG indexes in two directions,
length scale parameter, and initial gap are discussed in detail.
Key Words
2D-FGM; DQM; length scale parameter; micro-switch; pull-in instability
Address
Rahim Vesal and Ahad Amiri:School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran
Abstract
The principal goal of the present study is to examine the aeroelastic analysis of cylindrical laminated shells with
curvilinear fibers. To attain this objective, the equations of motion are firstly extracted according to the first-order shear
deformation theory (FSDT). The linear piston theory is then implemented to estimate aerodynamic loads for various airflow
angles over the cylindrical shell area, providing the aeroelastic equations. The well-known isogeometric analysis based on the
NURBS basis functions is subsequently developed to discretize the aeroelastic equations of the considered problem. Finally, by
writing the resultant equations in the standard form of an eigenvalue problem, the panel flutter analysis of a cylindrical variable
stiffness composite laminated (VSCL) shell will be carried out. The comparison and validation of achieved results with the
results of references mentioned in the literature are made to demonstrate the accurateness of the present formulation. Also, the
influence of various parameters, including the airflow angle, fiber path orientation, radius of curvature, and converting
symmetric lay-up to unsymmetrical lay-up on the flutter threshold is studied.
Abstract
This study uses the state-space approach to study the bending behavior of Levy-type functionally graded (FG) plates
sandwiched between two piezoelectric layers. The coupled governing equations are obtained using Hamilton's principle and
Maxwell's equation based on the efficient four-variable refined plate theory. The partial differential equations (PDEs) are
converted using Levy's solution technique to ordinary differential equations (ODEs). In the context of the state-space method,
the higher-order ODEs are simplified to a system of first-order equations and then solved. The results are compared with those
reported in available references and those obtained from Abaqus FE simulations, and good agreements between results confirm
the accuracy and efficiency of the approach. Also, the effect of different parameters such as power-law index, aspect ratio, type
of boundary conditions, thickness-to-side ratio, and piezoelectric thickness are studied.
Abstract
This study examines the seismic vulnerability of vertically irregular reinforced concrete (RC) frame buildings,
focusing on the effectiveness of retrofitting techniques such as rocking walls (RWs) in mitigating soft story mechanisms.
Utilizing a seven-story residential apartment as a prototype in a high-seismicity urban area, this research performs detailed
nonlinear simulations to evaluate both regular and irregular structures, both before and after retrofitting. Pushover and nonlinear
time history analyses were conducted using OpenSees software, with a suite of nine ground motion records to capture diverse
seismic scenarios. The findings indicate that retrofitting with RWs significantly improves seismic performance: for instance, roof
displacements at the Collapse Prevention (CP) level decreased by up to 23% in the irregular structure with retrofitting compared
to its non-retrofitted counterpart. Additionally, interstory drift ratios were more uniform post-retrofit, with Drift Concentration
Factor (DCF) values approaching 1.0 across all performance levels, reflecting reduced variability in seismic response. The
global ductility of the retrofitted buildings improved, with displacement ductility ratios increasing by up to 29%. These results
underscore the effectiveness of RWs in enhancing global ductility, mitigating soft story failures, and providing a more
predictable deformation pattern during seismic events. The study thus provides valuable insights into the robustness and costeffectiveness of using rocking walls for retrofitting irregular RC buildings.
Key Words
irregular buildings; numerical simulation; rocking walls; seismic retrofit; soft story failure
Address
Tadeh Zirakian:Department of Civil Engineering and Construction Management, California State University, Northridge, U.S.A.
Omid Parvizi:Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran
Mojtaba Gorji Azandariani:Centre for Infrastructure Engineering, Western Sydney University, Penrith, NSW, Australia
David Boyajian:Department of Civil Engineering and Construction Management, California State University, Northridge, U.S.A.
Abstract
Nonlinear internal modals interactions analysis of axially functionally graded nanorods is evaluated on the basis of
nonlocal elasticity theory and Rayleigh beam model for the first time. Functionally graded materials can be determined as
nonhomogeneous composites which are obtained by combining of two various materials in order to get a new ideal material. In
this research, material properties of nanorods are supposed to be calmly varied along the axial direction. Hamilton's principle is
used to derive the equations with consideration of Von–Karman's geometrically nonlinearity. Harmonic Differential Quadrature
(HDQ) and Multiple Scale (MS) solution techniques are used to derive an approximate-analytic solution to the linear and
nonlinear free axial vibration problem of non-classical nanorods for clamped–clamped and clamped-free boundary conditions. A
parametric study is carried out to indicate the effects of index of AFG, aspect ratio, mode number, internal resonances and
nonlinear amplitude on nonlinear nonlocal frequencies of axially functionally graded nanorods. Also, the effects of nonlocal and
nonlinear coefficients and AFG index on relationships of internal resonances have been investigated. The presented theatricalsemi analytical model has the ability to predict very suitable results for extracting the internal modal interactions in the AFG
nanorod.
Key Words
AFG nanorod; non-linear vibrations; nonlocal elasticity theory; Rayleigh model; relationships of internal
resonances
Address
Somaye Jamali Shakhlavi:1)School of Engineering, Westlake University, Hangzhou, China
2) School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran
Shahrokh Hosseini Hashemi:School of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran, Iran
Reza Nazemnezhad:School of Engineering, Damghan University, Damghan, Iran
Abstract
After a disaster like the catastrophic earthquake, the government have to use rapid assessment of the condition (or
damage) of bridges, buildings and other infrastructures is mandatory for rapid feedbacks, rescue and post-event management.
This work studies the tracking control problem of a class of strict-feedback nonlinear systems with input saturation nonlinearity.
Under the framework of dynamic surface control design, RBF neural networks are introduced to approximate the unknown
nonlinear dynamics. In order to address the impact of input saturation nonlinearity in the system, an auxiliary control system is
constructed, and by introducing a class of first-order low-pass filters, the problems of large computation and computational
explosion caused by repeated differentiation are effectively solved. In response to unknown parameters, corresponding adaptive
updating control laws are designed. The goals of this paper are towards access to adequate, safe and affordable housing and basic
services, promotion of inclusive and sustainable urbanization and participation, implementation of sustainable and disasterresilient buildings, sustainable human settlement planning and manage. Simulation results of linear and nonlinear structures
show that the proposed method is able to identify structural parameters and their changes due to damage and unknown
excitations. Therefore, the goal is believed to achieved in the near future by the ongoing development of AI and control theory.
Key Words
AI Kalman filter; damage resilience; dynamic surface control; fuzzy control; input saturation; nonlinear
analysis; strict-feedback nonlinear systems
Address
ZY Chen:Sch Sci Guangdong University of Petrochem Technol, Maoming, Guangdong, China
Yahui Meng:Sch Sci Guangdong University of Petrochem Technol, Maoming, Guangdong, China
Huakun Wu:School of Computer Science, Guangdong Polytechnic Normal University, Guangzhou, Guangdong, China
ZY Gu:Sch Sci Guangdong University of Petrochem Technol, Maoming, Guangdong, China
Timothy Chen:Division of Eng App Sci, Caltech, CA 91125, U.S.A.
Abstract
The present paper deals with the dynamic analysis of cracked ceramic-reinforced aluminum composite fixed beams
by using a method based on changes in modal strain energy. Mechanical characteristics of composite materials of the beams are
predicted through Mori-Tanaka micromechanical scheme. A Comparative study and numerical simulations involve various
parameters; ceramic volume fraction, reinforcement aspect ratio, ratio of the reinforcement Young
Key Words
aluminum; ceramic; composite beam; crack; vibration
Address
Abdellatif Selmi:1)Prince Sattam Bin Abdulaziz University, College of Engineering, Department of Civil Engineering, Alkharj, 11942, Saudi Arabia
2)Ecole Nationale d'Ingénieurs de Tunis (ENIT), Civil Engineering Laboratory. B.P. 37, Le belvédère 1002, Tunis, Tunisia
Abstract
This study presents a static analysis of thin shallow cylindrical and spherical panels, as well as plates (which are a
special case of shells), under Levy-type mixed boundary conditions and various loading conditions. The study utilizes the
boundary discontinuous double Fourier series method, where displacements are expressed as trigonometric functions, to analyze
the system of partial differential equations. The panels are subjected to a simply supported type 3 (SS3) boundary condition on
two opposite edges, while the remaining two edges are subjected to clamped type 3 (C3) boundary conditions. The study
presents comprehensive tabular and graphical results that demonstrate the effects of curvature on the deflections and moments of
thin shallow shells made from symmetric and antisymmetric cross-ply laminated composites, as well as isotropic steel materials.
The proposed model is validated through comparison with existing literature, and the convergence characteristics are
demonstrated. The changing trends of displacements and moments are explained in detail by investigating the effect of various
parameters, such as stacking lamination, material types, curvature, and loading conditions.
Key Words
analytical solution; boundary discontinuous Fourier analysis; classical lamination theory; composite plates
composite shells; Levy type boundary condition
Address
Ahmet Sinan Öktem and Ιlke Algüla:Department of Mechanical Engineering, Gebze Technical University, Gebze Kocaeli, Turkey
