Techno Press
Tp_Editing System.E (TES.E)
Login Search


sem
 
CONTENTS
Volume 35, Number 4, July10 2010
 

Abstract
In this paper, using perturbation and Galerkin method, the response of a resonant viscoelastic microbeam to an electric actuation is obtained. The microbeam is under axial load and electrical load. It is assumed that midplane is stretched, when the beam is deflected. The equation of motion is derived using the Newton\'s second law. The viscoelastic model is taken to be the Kelvin-Voigt model. In the first section, the static deflection is obtained using the Galerkin method. Exact linear symmetric mode shape of a straight beam and its deflection function under constant transverse load are used as admissible functions. So, an analytical expression that describes the static deflection at all points is obtained. Comparing the result with previous research show that using deflection function as admissible function decreases the computation errors and previous calculations volume. In the second section, the response of a microbeam resonator system under primary and secondary resonance excitation has been obtained by analytical multiple scale perturbation method combined with the Galerkin method. It is shown, that a small amount of viscoelastic damping has an important effect and causes to decrease the maximum amplitude of response, and to shift the resonance frequency. Also, it shown, that an increase of the DC voltage, ratio of the air gap to the microbeam thickness, tensile axial load, would increase the effect of viscoelastic damping, and an increase of the compressive axial load would decrease the effect of viscoelastic damping.

Key Words
viscoelastic damping; static deflection; mode shape; resonance excitation; perturbation methods; Galerkin method.

Address
M. Zamanian: Mechanical & Aerospace Engineering Department, Tarbiat Modares University, Tehran, Iran
S.E. Khadem: Mechanical & Aerospace Engineering Department, Tarbiat Modares University, Tehran, Iran
S.N. Mahmoodi: Center for Vehicle Systems & Safety, Department of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, USA

Abstract
The present paper will be concerned to the investigation of the stress-strain field around the cavity that is loaded or partially loaded at the inner surface by the rotationally symmetric loading. The cavity of the spherical, cylindrical or elliptical shape is situated in a stressed elastic continuum, subjected to the gravitation field. As the contribution to the similar investigations, the paper introduces the new function of loading in the form of the infinite sine series. Besides, in this paper the solution of stresses around an oblong ellipsoid cavity, has been obtained using appropriate curvilinear elliptical coordinates. This analytical approach avoids the solutions of the same problem that lead to expressions that contain rather complex integrations. Thus the presented solutions provide the applicable and explicit expressions for stresses and strains developed in infinite series with easily determinable coefficients by the use of contemporary mathematical packages. The numerical examples are also included to confirm the convergence of the obtained solutions.

Key Words
continuum; cavity; partially supported boundary; loading function.

Address
D. Lukic: Faculty of Civil Engineering Subotica, University of Novi Sad, Subotica 24000, Serbia
A. Prokic: Faculty of Civil Engineering Subotica, University of Novi Sad, Subotica 24000, Serbia
P. Anagnosti: Faculty of Civil Engineering Belgrade, University of Belgrade, Belgrade 11000, Serbia

Abstract
This article provides a discussion of the mathematic modeling of connections for designing and qualifying structures, systems, and components subject to monotonic or cyclic loading. To characterize the force-deformation behavior of connections under monotonic loading, a review of the Ramberg-Osgood, Richard-Abbott, and Menegotto-Pinto models is conducted, and it is shown that these nonlinear functions can be mathematically derived by scaling up or down a linear force-deformation function. A generalized four-parameter model for simulating connection behavior is investigated to facilitate nonlinear regression analysis. In order to perform seismic analysis of frameworks, a hysteretic model accounting for loading, unloading, and reloading is described using the established monotonic model. For preliminary analysis, a method is provided to quickly determine the model parameters that fit approximately with the observed data. To reach more accurate values of the parameters, the methods of nonlinear regression analysis are investigated and the modified Levenberg-Marquardt and separable nonlinear least-square algorithms are applied in determining the model parameters. Example case studies illustrate the procedure for the computation through the use of experimental/analytical data taken form the literature. Transformation of connection curves from the three-parameter model to the four-parameter model for structural analysis is conducted based on the modeling of connections subject to fire.

Key Words
connection models; monotonic/cyclic loading; force-deformation relation; observed data; nonlinear regression analysis.

Address
Yuxin Liu: ACR Civil & Layout, Atomic Energy of Canada Limited (AECL), Ontario L5K 1B2, Canada

Abstract
This paper contains detailed descriptions of a dynamic time-history modal analysis to calculate deflection, inter-storey drift and storey shear demand in single-storey and multi-storey buildings using an EXCEL spreadsheet. The developed spreadsheets can be used to obtain estimates of the dynamic response parameters with minimum input information, and is therefore ideal for supporting the conceptual design of tall building structures, or any other structures, in the early stages of the design process. No commercial packages, when customised, could compete with spreadsheets in terms of simplicity, portability, versatility and transparency. An innovative method for developing the stiffness matrix for the lateral load resistant elements in medium-rise and high-rise buildings is also introduced. The method involves minimal use of memory space and computational time, and yet allows for variations in the sectional properties of the lateral load resisting elements up the height of the building and the coupling of moment frames with structural walls by diaphragm action. Numerical examples are used throughout the paper to illustrate the development and use of the spreadsheet programs.

Key Words
seismic; storey drift; EXCEL; dynamic modal analysis; tall buildings.

Address
Nelson Lam: Department of Civil & Environmental Engineering, University of Melbourne, Parkville, Victoria, Australia
John Wilson: Faculty of Engineering and Industrial Science, Swinburne University of Technology, Hawthorn, Victoria, Australia
Elisa Lumantarna: Department of Civil & Environmental Engineering, University of Melbourne, Parkville, Victoria, Australia

Abstract
Advances in geological studies, have identified increased seismic activity in the world\'s ocean once believed to be far from seismic hazards. The increase in demand of oil and other hydrocarbons leaves no option but to install a suitable offshore platform on these seismically sensitive offshore basins. Therefore, earthquake based design criteria for offshore structures are essential. The focus of the present review is on various computational techniques involved for seismic response study. The structural and load modeling approaches, the disturbed fluid-structure and soil-structure interaction as well as hydrodynamic damping due to earthquake excitation are also discussed. A brief description on the reliability-based seismic design approach is also presented.

Key Words
response spectrum; hydrodynamic damping; soil-structure interaction; reliability.

Address
Syed Danish Hasan: Civil Engineering Section, University Polytechnic, AMU Aligarh, India
Nazrul Islam: Civil Engineering Department, Jamia Millia Islamia, New Delhi, India
Khalid Moin: Civil Engineering Department, Jamia Millia Islamia, New Delhi, India

Abstract
This paper presents effects of anisotropy and curvature on free vibration characteristics of cross-ply laminated composite cylindrical shallow shells. Shallow shells have been considered for different lamination thickness, radius of curvature and elasticity ratio. First, kinematic relations of strains and deformation have been showed. Then, using Hamilton\'s principle, governing differential equations have been obtained for a general curved shell. In the next step, stress-strain relation for laminated, cross-ply composite shells has been given. By using some simplifications and assuming Fourier series as a displacement field, differential equations are solved by matrix algebra for shallow shells. The results obtained by this solution have been given tables and graphs. The comparisons made with the literature and finite element program (ANSYS).

Key Words
structural composites; vibration; anisotropy; shell theory; finite element method (FEM).

Address
Ali Dogan: Department of Civil Engineering, Cukurova University, 01330 Adana, Turkey
H. Murat Arslan: Department of Civil Engineering, Cukurova University, 01330 Adana, Turkey
Huseyin R. Yerli: Department of Civil Engineering, Cukurova University, 01330 Adana, Turkey

Abstract
As a truly meshfree method, meshless equilibrium on line method (MELM), for 2D elasticity problems is presented. In MELM, the problem domain is represented by a set of distributed nodes, and equilibrium is satisfied on lines for any node within this domain. In contrary to conventional meshfree methods, test domains are lines in this method, and all integrals can be easily evaluated over straight lines along x and y directions. Proposed weak formulation has the same concept as the equilibrium on line method which was previously used by the authors for enforcement of the Neumann boundary conditions in the strong-form meshless methods. In this paper, the idea of the equilibrium on line method is developed to use as the weak forms of the governing equations at inner nodes of the problem domain. The moving least squares (MLS) approximation is used to interpolate solution variables in this paper. Numerical studies have shown that this method is simple to implement, while leading to accurate results.

Key Words
computational mechanics; meshfree methods; equilibrium on line method (MELM); moving least squares (MLS) approximation; elasticity.

Address
A. Sadeghirad: School of Civil Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, Iran
S. Mohammadi: School of Civil Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, Iran
I. Mahmoudzadeh Kani: School of Civil Engineering, University of Tehran, P.O. Box 11365-4563, Tehran, Iran

Abstract


Key Words


Address
Bretislav Teply: Brno University of Technology, Faculty of Civil Engineering, CIDEAS Research Centre, Veve i 95, 602 00 Brno, Czech Republic
Dita Vorechovska: Brno University of Technology, Faculty of Civil Engineering, CIDEAS Research Centre, Veve i 95, 602 00 Brno, Czech Republic
Zbynek Kersner: Brno University of Technology, Faculty of Civil Engineering, CIDEAS Research Centre, Veve i 95, 602 00 Brno, Czech Republic


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com