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CONTENTS
Volume 4, Number 4, December 2011
 

Abstract
Understanding the structural stability of carbon nanostructure under heat treatment is critical for tailoring the thermal properties of carbon-based material at small length scales. We investigate the heat resistance of the single carbon nanoball (C60) and carbon nanoonions (C20@C80, C20@C80@C180, C20@C80@C180C320) by performing molecular dynamics simulations. An empirical many-body potential function, Tersoff potential, for carbon is employed to calculate the interaction force among carbon atoms. Simulation results shows that carbon nanoonions are less resistive against heat treatment than single carbon nanoballs. Single carbon nanoballs such C60 can resist heat treatment up to 5600 K, however, carbon nanoonions break down after 5100 K. This intriguing result offers insights into understanding the thermal-mechanical coupling phenomena of nanodevices and the complex process of fullerenes

Key Words
molecular dynamics; carbon nanoballs; carbon nanoonions; heat resistance; tersoff potential.

Address
Xianqiao Wang and James D. Lee: Department of Mechanical and Aerospace Engineering, The George Washington University,
Washington, DC 20052, USA

Abstract
The analysis of interfacial stresses in structural component has been the subject of several investigations but it still requires more effort and studies. In this study a general three-dimensional interface element has been formulated for stress and displacement analyses in the interfacial area between two adjacent plate bending element and brick element. Interface element has 16 nodes with 5 degrees of freedom (DOF) in each node adjacent to plate bending element and 3 DOF in each node adjacent to brick element. The interface element has ability to transfer three translations from each side of interface element and two rotations in the side adjacent to the plate element. Stiffness matrix of this element was formulated and implemented in three-dimensional finite element code. Application of this element to the reinforced concrete (RC) beam strengthened with fiber reinforced polymer (FRP) including variation of deflection, slip between plate and concrete, normal and shear stresses distributions in FRP plates have been verified using experimental and numerical work of strengthened RC beams carried out by some researchers. The results show that this interface element is effective and can be used for structural component with these types of interface elements.

Key Words
interface element; bond; plate bending element; three dimensional; FRP.

Address
O. Kohnehpooshi: Department of Civil Engineering, Universiti Putra Malaysia, 43400-Serdang, Malaysia
J. Noorzaei: Institute of Advance Technology, Universiti Putra Malaysia, 43400-Serdang, Malaysia
M.S. Jaafar and M.R.R. Saifulnaz: Department of Civil Engineering, Universiti Putra Malaysia, 43400-Serdang, Malaysia

Abstract
The vibration response of the bridges under the moving vehicular load is of importance for engineers to estimate the serviceability of existing bridges and to design new bridges. This paper deals with the three dimensional vibration analysis of prestressed concrete bridges under moving vehicles. The prestressed bridges are modeled by four-node isoparametric flat shell elements with the transverse shearing deformation taken into account. The usual five degrees-of-freedom (DOFs) per node of the element are appended with a drilling DOF to accommodate the transformation of the local stiffness and mass matrices to the global coordinates. The vehicle is modeled as a single or two-DOF system. A single-span prestressed Tee beam and two-span prestressed box-girder bridge are studied as the two numerical examples. The effects of prestress forces on the natural frequencies and dynamic responses of the bridges are investigated.

Key Words
prestressed concrete bridge; flat shell element; drilling degree-of-freedom; box-girder; vehicle-bridge interaction.

Address
M. Huang: Research Center of Intelligent Transportation System, Sun Yat-sen University, Guangzhou, Guangdong Province, 510006, P.R.China
J.K. Liu: Department of Applied Mechanics and Engineering, Sun Yat-sen University, Guangzhou, Guangdong Province, 510006, P.R. China
S.S. Law: Civil and Structural Engineering Department, Hong Kong Polytechnic University, Hunghom, Kowloon, Hong Kong, P.R. China
Z.R. Lu: Department of Applied Mechanics and Engineering, Sun Yat-sen University, Guangzhou, Guangdong Province, 510006, P.R. China

Abstract
To simulate the self excited torsional vibrations of rotating drill strings (DSs) in vertical bore-holes, the nonlinear wave models of homogeneous and sectional torsional pendulums are formulated. The stated problem is shown to be of singularly perturbed type because the coefficient appearing before the second derivative of the constitutive nonlinear differential equation is small. The diapasons

Key Words
drill strings; multiscale dynamics; relaxation vibration; singularly perturbed problem; torsional vibration.

Address
V.I. Gulyayev and O.V. Glushakova: Department of Mathematics, National Transport University, Suvorov str., 1 Kiev, 01010, Ukraine

Abstract
This paper proposes an approximate formulation to estimate the bifurcation buckling loads of cylindrical shells with soft elastic cores under the conditions of axial compression. In general, thin-walled, axially compressed cylindrical shells buckle into a diamond pattern in the elastic range. However, buckling symmetrical with respect to the axis of the cylinder may occur when the cylindrical shell is supported by an elastic medium. By considering this characteristic, we introduce the simplified approximate formulation that can give sufficiently accurate results for the bifurcation buckling loads of cylindrical shells. Moreover the results are compared with the exact buckling loads in order to confirm the accuracy of the proposed approximate formulation.

Key Words
cylindrical shell; bifurcation buckling; elastic medium.

Address
Motohiro Sato and Kenta Shimazaki: Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan

Abstract
This paper presents the results of static vertical load tests carried out on a model building frame supported by pile groups embedded in cohesionless soil (sand). The effect of soil interaction on displacements and rotation at the column base and also the shears and bending moments in the columns of the building frame were investigated. The experimental results have been compared with those obtained from the finite element analysis and conventional method of analysis. Soil nonlinearity in the lateral direction is characterized by the p-y curves and in the axial direction by nonlinear vertical springs along the length of the piles (

Key Words
soil interaction; experimental analysis; pile group; building frame; cohesionless soil.

Address
C. Ravi Kumar Reddy and T.D. Gunneswara Rao: Department of Civil Engineering, National Institute of Technology,
Warangal, India - 506004


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