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CONTENTS
Volume 34, Number 4, March10 2010
 

Abstract
The purpose of this paper is to utilize the numerical assembly method (NAM) to determine the exact natural frequencies and mode shapes of a multi-step beam carrying multiple rigid bars, with each of the rigid bars possessing its own mass and rotary inertia, fixed to the beam at one point and supported by a translational spring and/or a rotational spring at another point. Where the fixed point of each rigid bar with the beam does not coincide with the center of gravity the rigid bar or the supporting point of the springs. The effects of the distance between the \"fixed point\" of each rigid bar and its center of gravity (i.e., eccentricity), and the distance between the \"fixed point\" and each linear spring (i.e., offset) are studied. For a beam carrying multiple various concentrated elements, the magnitude of each lumped mass and stiffness of each linear spring are the well-known key parameters affecting the free vibration characteristics of the (loaded) beam in the existing literature, however, the numerical results of this paper reveal that the eccentricity of each rigid bar and the offset of each linear spring are also the predominant parameters.

Key Words
rigid bar; numerical assembly method; exact solution; natural frequency; mode shape; eccentricity; offset.

Address
Hsien-Yuan Lin: Department of Mechanical Engineering, Cheng Shiu University, Kaohsiung 83347, Taiwan, R.O.C.

Abstract
The uncertainty often observed in experimental strengths of masonry constituents makes critical the selection of the appropriate inputs in finite element analysis of complex masonry buildings, as well as requires modelling the building ultimate load as a random variable. On the other hand, the utilization of expensive Monte Carlo simulations to estimate collapse load probability distributions may become computationally impractical when a single analysis of a complex building requires hours of computer calculations. To reduce the computational cost of Monte Carlo simulations, direct computer calculations can be replaced with inexpensive Response Surface (RS) models. This work investigates the use of RS models in Monte Carlo analysis of complex masonry buildings with random input parameters. The accuracy of the estimated RS models, as well as the good estimations of the collapse load cumulative distributions obtained via polynomial RS models, show how the proposed approach could be a useful tool in problems of technical interest.

Key Words
Monte Carlo method; masonry; limit analysis; homogenization; polynomial Response Surface; Latin Hypercube method; collapse load probability distribution.

Address
G. Milani: DIS, Dipartimento di Ingegneria Strutturale, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan, Italy
D. Benasciutti: DIEGM, Dipartimento di Ingegneria Elettrica Gestionale Meccanica, University of Udine, Via delle Scienze 208, 33100 Udine, Italy

Abstract
A smart hollow cylinder consisting of a host functionally graded elastic core layer and two surface homogeneous piezoelectric layers is presented in this paper. The bonding between the layers can be perfect or imperfect, depending on the parameters taken in the general linear spring-layer interface model. The effect of such weak interfaces on free vibration and steady-state response is then investigated. Piezoelectric layers at inner and outer surfaces are polarized axially or radially and act as a sensor and an actuator respectively. For a simply supported condition, the state equations with non-constant coefficients are obtained directly from the formulations of elasticity/piezoelasticity. An approximate laminated model is then introduced for the sake of solving the state equations conveniently. It is further assumed that the hollow cylinder is embedded in an elastic medium and is simultaneously filled with compressible fluid. The interaction between the structure and its surrounding media is taken into account. Numerical examples are finally given with discussions on the effect of some related parameters.

Key Words
free vibration; steady-state response; smart cylinder; interaction; imperfect interfaces; spring-layer model; state space approach.

Address
Z.G. Bian: Department of Civil Engineering, Ningbo Institute of Technology, Zhejiang University, Ningbo 315100, P.R. China
W.Q. Chen: Institute of Applied Mechanics, Zhejiang University, Hangzhou 310027, P.R. China
J. Zhao: Quzhou Highway Management Department, Quzhou 324000, P.R. China

Abstract
It is the intention of this study to synthesize the effects of double-edge cracks on the dynamic characteristics of a beam. The stiffness matrix is first determined for a Timoshenko beam containing two same-line edge cracks. The presented model is then developed for elements with two parallel double-sided cracks, considering the interaction between the stress fields of adjacent cracks. Finally, a finite element code is implemented, to examine the influence of depth and location of double cracks, on the natural frequencies of the damaged system.

Key Words
crack identification; Timoshenko beam; free vibration; flexibility matrix; double-sided cracks.

Address
M.R. Ayatollahi: Fatigue and Fracture Laboratory, Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846, Iran
R. Hashemi:Fatigue and Fracture Laboratory, Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846, Iran
H. Rokhi: Fatigue and Fracture Laboratory, Department of Mechanical Engineering, Iran University of Science and Technology, Narmak, Tehran 16846, Iran

Abstract
A computational analysis of the nonlinear free vibration of corrugated annular plates with shallow sinusoidal corrugations under uniformly static ambient temperature is examined. The governing equations based on Hamilton\'s principle and nonlinear bending theory of thin shallow shell are established for a corrugated plate with a concentric rigid mass at the center and rotational springs at the outer edges. A simple harmonic function in time is assumed and the time variable is eliminated from partial differential governing equations using the Kantorovich averaging procedure. The resulting ordinary equations, which form a nonlinear two-point boundary value problem in spatial variable, are then solved numerically by shooting method, and the temperature-dependent characteristic relations of frequency vs. amplitude for nonlinear vibration of heated corrugated annular plates are obtained. Several numerical results are presented in both tabular and graphical forms, which demonstrate the accuracy of present method and illustrate the amplitude frequency dependence for the plate under such parameters as ambient temperature, plate geometry, rigid mass and elastic constrain.

Key Words
corrugated annular plate; nonlinear vibration; temperature change; elastic constraint; central rigid mass; shooting method.

Address
Yong-Gang Wang: Department of Applied Mechanics, China Agricultural University, Beijing 100083, P.R. China
Dan Li: Department of Applied Mechanics, China Agricultural University, Beijing 100083, P.R. China
Ze-Jun Feng: Department of Applied Mechanics, China Agricultural University, Beijing 100083, P.R. China

Abstract
Parametric and forced non-linear vibrations of an axially moving rotor both in non-resonance and near-resonance cases have been investigated analytically in this paper. The axial speed is assumed to involve a mean value along with small harmonic fluctuations. Hamilton

Key Words
non-linear vibrations; multiple-scale method; axially moving rotor.

Address
Mergen H. Ghayesh: Department of Mechanical Engineering, McGill University, 817 Sherbrooke St. West, Montreal, Quebec H3A 2K6, Canada
Mohammad R. Ghazavi: Mechanical Engineering Department, School of Engineering, Tarbiat Modarres University, Tehran, Iran
Siamak E. Khadem: Mechanical Engineering Department, School of Engineering, Tarbiat Modarres University, Tehran, Iran

Abstract
Polymer matrix composites are widely used in many engineering applications as they can be customized to meet a desired performance while not only maintaining low cost but also reducing weight. Polymers can experience viscoelastic-viscoplastic response when subjected to external loadings. Various reinforcements and fillers are added to polymers which bring out more complexity in analyzing the timedependent response. This study formulates an integrated micromechanical model and finite element (FE) analysis for predicting effective viscoelastic-viscoplastic response of polymer based hybrid composites. The studied hybrid system consists of unidirectional short-fiber reinforcements and a matrix system which is composed of solid spherical particle fillers dispersed in a homogeneous polymer constituent. The goal is to predict effective performance of hybrid systems having different compositions and properties of the fiber, particle, and matrix constituents. A combined Schapery

Key Words
viscoelasticity; viscoplasticity; micromechanics; homogenization; hybrid composite.

Address
Jeongsik Kim: Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123, USA
Anastasia Muliana: Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123, USA

Abstract


Key Words


Address
K.S. Babu Narayan: Department of Civil Engineering, National Institute of Technology Karnataka Surathkal,
Srinivasnagara - 575 025, India

Abstract


Key Words


Address
S.Y. Ren: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China
Lin Tung-Yen & Li Guo-Hao Consultants Shanghai Ltd., Shanghai 200092, China
M. Gu: State Key Laboratory of Disaster Reduction in Civil Engineering, Tongji University, Shanghai 200092, China


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