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CONTENTS
Volume 26, Number 2, May30 2007
 

Abstract
Dynamic responses of the bridge for a straddle-type monorail subjected to the ground motion of high probability to occur are investigated by means of a three-dimensional traffic-induced vibration analysis to clarify the effect of a train?s dynamic system on seismic responses of a monorail bridge. A 15DOFs model is assumed for a car in the monorail train. The validity of developed equations of motion for a monorail train-bridge interaction system is verified by comparison with the field-test data. The inertia effect due to a ground motion is combined with the monorail train-bridge interaction system to investigate the seismic response of the monorail bridge under a moving train. An interesting result is that the dynamic system of the train on monorail bridges can act as a damper during earthquakes. The observation of numerical results also points out that the damper effect due to the dynamic system of the monorail train tends to decrease with increasing speed of the train.

Key Words
seismic response; damper effect; monorail train-bridge interaction; straddle-type monorail

Address
Department of Civil Engineering, Osaka University, Osaka 565-0871, Japan

Abstract
The objective of this paper is to develop a finite element procedure for predicting the compressive strength and ultimate axial strain of Carbon Fiber Reinforced Plastics (CFRP) confined circular concrete columns and to study the effective parameters of confinement efficiency for helping design of CFRP retrofit technology. The behavior of concrete confined with CFRP is studied using the nonlinear finite element method. In this paper, effects of column size, CFRP volumetric ratio and plain concrete strength are studied. The confined concrete nonlinear constitutive relation, concrete failure criterion and stiffness reduction methodology after concrete cracking or crushing are adopted. First, the finite element model is verified by comparing the numerical solutions of confined concrete with experimental results. Then the effects of column size, CFRP volumetric ratio and plain concrete strength on the peak strength and ductility of the confined concrete are considered. The results of parametric study indicate that the normalized column axial strength increases with increasing CFRP volumetric ratio, but without size effect for columns with the same CFRP volumetric ratio. As the same, the increase in column ductility depends on CFRP volumetric ratio but without size effect for columns with the same CFRP volumetric ratio

Key Words
FRP; strength of confined concrete; ductility; confinement efficiency; size effect

Address
Fang-Yao Yeh; Photovoltaic Technology Center, Industrial Technology Research Institute, Taiwan, 310, R.O.C.
Kuo-Chun Chang; Dept. of Civil Engineering, National Taiwan University, Taipei, Taiwan, 10617, R.O.C.

Abstract
Rigorous analytical solutions are obtained for the plane stress problem of a rectangular plate subjected to non-linearly distributed bending loads on two opposite edges. They are then used in a Galerkin type solution to obtain the corresponding convergent buckling loads. It is shown that the critical bending moment depends significantly on the actual edge load distribution and further the number of nodal lines of the buckled configuration can also be different from that corresponding to a linear antisymmetric distribution of the bending stresses. Results are tabulated for future use while judging approximate numerical solutions.

Key Words
buckling; rectangular plates; in-plane bending; non-linear edge stress distribution; two-dimensional elasticity; analytical solutions

Address
Aerospace Engineering Department, IIT, Madras, Chennai – 600 036, India

Abstract
In practical engineering, the uncertain concept plays an important role in the control problems of the vibration structures. In this paper, based on matrix perturbation theory and interval finite element method, the closed-loop vibration control system with uncertain parameters is discussed. A new method is presented to develop an algorithm to estimate the upper and lower bounds of the real parts and imaginary parts of the complex eigenvalues of vibration control systems. The results are derived in terms of physical parameters. The present method is implemented for a vibration control system of the frame structure. To show the validity and effectiveness, we compare the numerical results obtained by the present method with those obtained by the classical random perturbation.

Key Words
matrix perturbation method; interval finite element; stability robustness; random perturbation; uncertain closed-loop system

Address
School of Mechanical Engineering, Shanghai Jiao Tong University, Huashan Road, Shanghai, 200030, P. R. China

Abstract
Damage detection based on measured vibration data has received intensive studies recently. Frequently, the damage to a structure may be reflected by a change of some system parameters, such as a degradation of the stiffness. In this paper, we apply a method to nondestructively locate and estimate the severity of damage in corrosion pipeline for which a few natural frequencies or mode shapes are available. The method is based on the strain modal sensitivity ratio (SMSR) and the orthogonality conditions sensitivities (OCS) applied to vibration features identified during the monitoring of the pipeline. The advantage of these methods is that it only requires measuring few modal parameters. The SMSR-based and OCS-based damage detection methods are illustrated using computer-simulated and laboratory testing data. The results show that the current method provides a precise indication of both the location and the extent of corrosion pipeline

Key Words
damage identification; corrosion pipeline; the strain modal sensitivity ratio; the orthogonality conditions sensitivities; mode shape

Address
Zhi-Rong Yang, Hong-Sheng Li and Xing-Lin Guo; Dept. of Engineering Mechanics, Dalian University of Technology, Dalian, 116024, P.R. China
Hong-Yan Li; Dalian Inspection Institute of Boiler Pressure Container, Dalian, 116013, P.R. China

Abstract
The three different approaches (reformulations) of evolution strategies (ESs) have been proposed in the literature as extensions of the technique for solving discrete problems. This study implements an extensive research on application, evaluation and comparison of them in discrete optimum design of steel frames. A unified formulation is first developed to explain these approaches, so that differences and similarities between their inherent search mechanisms can clearly be identified. Two examples from practical design of steel frames are studied next to measure their performances in locating the optimum. Extensive numerical experimentations are performed in both examples to facilitate a statistical analysis of their convergence characteristics. The results obtained are presented in the histograms demonstrating the distribution of the best designs located by each approach. In addition, an average improvement of the best design during the course of evolution is plotted in each case to compare their relative convergence rates.

Key Words
structural optimization; evolution strategies; discrete optimization; steel frames

Address
Department of Civil Engineering, Middle East Technical University, 06531 Ankara, Turkey

Abstract
An experimental investigation to determine the transfer length of a seven-wire prestressing strand in different concretes is presented in this paper. A testing technique based on the analysis of bond behaviour by means of measuring the force supported by the prestressing strand on a series of specimens with different embedment lengths has been used. An analytical bond model to calculate the transfer length from an inelastic bond stress distribution along the transfer length has been obtained. A relationship between the plastic bond stress for transfer length and the concrete compressive strength at the time of prestress transfer has been found. An equation to predict the average and both the lower bound and the upper bound values of transfer length is proposed. The experimental results have not only been compared with the theoretical prediction from proposed equations in the literature, but also with experimental results obtained by several researchers.

Key Words
bond; concrete; pretensioning; prestress; transfer length; strand; model

Address
Dept. of Construction Engineering and Civil Engineering Projects, School of Civil Engineering,
Polytechnic University of Valencia, Camino de Vera s/n 46071 Valencia, Spain


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