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CONTENTS
Volume 5, Number 4, December 2012
 

Abstract
Cable-stayed bridges are often used in modern bridge engineering for connecting two geographical points of long distance. A special load case to cable-stayed bridges is earthquake, which can produce horizontal as well as vertical movements on the pylons of the bridge. These movements may be transient in nature, i.e., only resulting in the transient vibration of the bridge, but causing no damage consequences. In some extreme cases, they may cause permanent subsidence on one or more pylons of the bridge. In this paper, the effect of pylons

Key Words
cable-stayed bridges; pylon displacements; fault; pylon dynamic subsidence.

Address
I.G. Raftoyiannis, G.T. Michaltsos and T.G. Konstantakopoulos: Department of Civil Engineering, National Technical University of Athens, Greece

Abstract
Measuring the bridge frequencies indirectly from an instrumented test vehicle is a potentially powerful technique for its mobility and economy, compared with the conventional direct technique that requires vibration sensors to be installed on the bridge. However, road surface roughness may pollute the vehicle spectrum and render the bridge frequencies unidentifiable. The objective of this paper is to study such an effect. First, a numerical simulation is conducted using the vehicle-bridge interaction element to demonstrate how the surface roughness affects the vehicle response. Then, an approximate theory in closed form is presented, for physically interpreting the role and range of influence of surface roughness on the identification of bridge frequencies. The latter is then expanded to include the action of an accompanying vehicle. Finally, measures are proposed for reducing the roughness effect, while enhancing the identifiability of bridge frequencies from the passing vehicle response.

Key Words
bridge; frequency; identification; surface roughness; vehicle; vehicle-bridge interaction.

Address
Y.B. Yang, Y.C. Li and K.C. Chang: Department of Civil Engineering, National Taiwan University, Taipei, Taiwan

Abstract
In this paper, soil-structure interaction analysis has been presented for beams resting on multilayered geosynthetic-reinforced granular fill-soft soil system. The soft soil and geosynthetic reinforcements are idealized as nonlinear springs and elastic membranes, respectively. The governing differential equations are solved by finite difference technique and the results are presented in nondimensional form. It is observed from the study that use of geosynthetic reinforcement is not very effective for maximum settlement reduction in case of very rigid beam. Similarly the reinforcements are not effective for shear force reduction if the granular fill has very high shear modulus value. However, multilayered reinforced system is very effective for bending moment and differential settlement reduction.

Key Words
beams; flexural rigidity; multilayered geosynthetic reinforcement; soft soil; soil-structure interaction.

Address
Kousik Deb: Department of Civil Engineering, Indian Institute of Technology Kharagpur, Kharagpur - 721302, India

Abstract
In this paper the dynamic stiffness matrix method was used for the free vibration analysis of axially moving micro beam with constant velocity. The extended Hamilton\'s principle was employed to derive the governing differential equation of the problem using the modified couple stress theory. The dynamic stiffness matrix of the moving micro beam was evaluated using appropriate expressions of the shear force and bending moment according to the Euler-Bernoulli beam theory. The effects of the beam size and axial velocity on the dynamic characteristic of the moving beam were investigated. The natural frequencies and critical velocity of the axially moving micro beam were also computed for two different end conditions.

Key Words
dynamic stiffness matrix method; free vibration; axially moving micro-beam; modified couple stress theory.

Address
Bashir Movahedian: Department of Civil Engineering, Isfahan University of Technology, Isfahan 84156-83111, Iran

Abstract
A dissipative particle dynamics (DPD) simulation was presented to analyze surface wettability and contact angles of a droplet on a solid platform. The many-body DPD, capable of modeling vapor-liquid coexistence, was used to resolve the vapor-liquid interface of a droplet. We found a constant density inside a droplet with a transition along the droplet boundary where the density decreased rapidly. The contact angle of a droplet was extracted from the isosurfaces of the density generated by the marching cube and a spline interpolation of 2D cutting planes of the isosurfaces. A wide range of contact angles from 55o to 165o predicted by the normalized parameter (|ASL|/BSL) were reported. Droplet with the parameters |ASL| > 5.84BSL0.297 was found to be hydrophilic. If |ASL| was much smaller than 5.84BSL0.297, the droplet was found to be superhydrophobic.

Key Words
dissipative particle dynamics; contact angle; surface wettability; hydrophilic; hydrophobic.

Address
Tzung-Han Lin and Wen-Pin Shih: Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan; Chuin-Shan Chen: Department of Civil Engineering, National Taiwan University, Taipei, Taiwan


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