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CONTENTS
Volume 24, Number 5, November30 2006
 

Abstract
This article presents a unified analytical solution for the analysis of thermal deformations and stresses in elastic annular disks with arbitrary cross-sections of continuously variable thickness. The annular disk is assumed to be under steady heat flow conditions, in which the inner surface of the annular disk is at an initial temperature and the outer surface at zero temperature. The governing second-order differential equation is derived from the basic equations of the thermal annular disks and solved with the aid of some hypergeometric functions. Numerical results for thermal stresses and displacement are given for various annular disks. These disks include annular disks of thickness profiles in the form of general parabolic and exponential functions. Additional annular disks with nonlinearly variable thickness and uniform thickness are also included.

Key Words
annular disks; steady heat flow; variable thickness; different profiles.

Address
Department of Mathematics, Faculty of Science, King AbdulAziz University,
P.O. Box 80203, Jeddah 21589, Saudi Arabia

Abstract
This work gives an application of stochastic techniques for the optimization of stiffened plates in vibration. The search strategy consists of substituting, for finite element calculations in the optimization process, an approximate response from a Rayleigh-Ritz method. More precisely, the paper describes the use of a Rayleigh-Ritz method in creating function approximations for use in computationally intensive design optimization based on genetic algorithms. Two applications are presented; their deal with the optimization of stiffeners on plates by varying their positions, in order to maximize some natural frequencies, while having well defined dimensions. In other words, this work gives the fundamental idea of using a Ritz approximation to the response of a plate in vibration instead of finite element analysis.

Key Words
optimization; stiffened plates; genetic algorithms; Rayleigh-Ritz method; vibrations.

Address
Laboratorie Sols Solides Structures 3S, UMR CNRS C5521, Domaine Universitaire, BP n

Abstract
In this paper, first, the equations of motion for a rectangular isotropic plate have been derived. This derivation is based on the Von Karmann theory and the effects of shear deformation have been considered. Introducing an Airy stress function, the equations of motion have been transformed to a nonlinear coupled equation. Using Galerkin method, this equation has been separated into position and time functions. By means of the dimensional analysis, it is shown that the orders of magnitude for nonlinear terms are small with respect to linear terms. The Multiple Scales Method has been applied to the equation of motion in the forced vibration and free vibration cases and closed-form relations for the nonlinear natural frequencies, displacement and frequency response of the plate have been derived. The obtained results in comparison with numerical methods are in good agreements. Using the obtained relation, the effects of initial displacement, thickness and dimensions of the plate on the nonlinear natural frequencies and displacements have been investigated. These results are valid for a special range of the ratio of thickness to dimensions of the plate, which is a characteristic of the Multiple Scales Method. In the forced vibration case, the frequency response equation for the primary resonance condition is calculated and the effects of various parameters on the frequency response of system have been studied.

Key Words
multiple scales method; plate; nonlinear vibration; free vibration; force vibration; frequency response.

Address
Mechanical Engineering Department, Tarbiat Modares University, P.O. Box 14115-177, Tehran, Iran

Abstract
The paper presents results of parametric studies, and an overall approach for the design of a modular bridge system which incorporates a steel-reinforcement free concrete slab cast on top of carbon FRP stiffened deck panels which act as both structural formwork and flexural reinforcement, spanning between hollow box type FRP girders. Results of the parametric studies are highlighted to elucidate important relationships between critical configurational parameters and empirical equations based on numerical studies are presented. Results are discussed at the level of the individual deck and girder components, and as a slab-on-girder bridge system. An overall design methodology for the components and bridge system including critical performance checks is also presented.

Key Words
steel-free; fiber reinforced polymer; structural formwork; parametric study; design approach; modular bridge system.

Address
Lijuan Cheng; Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, USA
Vistasp M. Karbhari; Department of Structural Engineering, University of California, San Diego, La Jolla, CA 92093-0085, USA

Abstract
This paper describes a series of laboratory tests carried out to evaluate the influence of bed joint orientation on interlocking grouted stabilised mud-flyash brick masonry under uniaxial cyclic compressive loading. Five cases of loading at 0o, 22.5o, 45o, 67.5o and 90o with the bed joints were considered. The brick units and masonry system developed by Prof. S.N. Sinha were used in present investigation. Eighteen specimens of size 500 mm

Key Words
interlocking brick; grout; uniaxial; cyclic loading; envelope curve; common point; stability point; stress-strain hysteresis.

Address
Maqsud E. Nazar; Power Grid Corporation of India Ltd., Sector 29, Gurgaon (Haryana)-122001, India
S. N. Sinha; Civil Engineering Department, Indian Institute of Technology Delhi, New Delhi-110016, India

Abstract
The paper presents an effective stiffness model for deformational analysis of reinforced concrete cracked members in bending throughout the short-term loading up to the near failure. The method generally involves the analytical derivation of an effective moment of inertia based on the smeared crack technique. The method, in a simplified way, enables us to take into account the non linear properties of concrete, the effects of cracking and tension stiffening. A statistical analysis has shown that proposed technique is of adequate accuracy of calculated and experimental deflections data provided for beams with small, average and normal reinforcement ratios.

Key Words
RC cross section; effective moment of inertia; cracking; tension stiffening.

Address
Laboratory of Numerical Modelling, Vilnius Gediminas Technical University,
Sauletekio av. 11, LT-10223 Vilnius, Lithuania

Abstract
Stability of a cylindrical shell subject to a uniform axial compression, which is a power function of time, is examined within the framework of small strain elasto-plasticity. The material of the shell is incompressible and the effect of the elastic unloading is considered. Initially, employing the infinitesimal elastic-plastic deformation theory, the fundamental relations and Donnell type stability equations for a cylindrical shell have been obtained. Then, employing Galerkin

Key Words
elasto-plastic stability; cylindrical shell; time dependent compressive axial load; critical parameters.

Address
A. H. Sofiyev; Department of Civil Engineering, Suleyman Demirel University, Isparta, Turkey
E. Schnack; Institute of Solid Mechanics, Karlsruhe University, Karlsruhe, Germany
F. Demir; Department of Civil Engineering, Suleyman Demirel University, Isparta, Turkey

Abstract
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Key Words
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Address
M. Nakhaei; Environmental and Civil Engineering Department, Southern Methodist University, Dallas, TX 75275, USA
M. A. Ghannad; Department of Civil Engineering, Sharif University of Technology, P.O. Box 11365-9313, Tehran, Iran


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