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CONTENTS
Volume 30, Number 5, November30 2008
 

Abstract
This paper examines local vibrations in the stay cables of a cable-stayed bridge subjected to wind gusts. The wind loads, including the self-excited load and the buffeting load, are converted into
time-domain values using the rational function approximation and the multidimensional autoregressive process, respectively. The global motion of the girder, which is generated by the wind gusts, is analyzed using the modal analysis method. The local vibration of stay cables is calculated using a model in which an inclined cable is subjected to time-varying displacement at one support under global vibration. This model can consider both forced vibration and parametric vibration. The response characteristics of the local vibrations in the stay cables under wind gusts are described using an existing cable-stayed bridge. The results of the numerical analysis show a significant difference between the combined parametric and forced vibrations and the forced vibration.

Key Words
cable-stayed bridge; stay cables; parametric vibration; wind gust response.

Address
Qingxiong Wu: College of Civil Engineering, Fuzhou University, No. 2 Xueyuan Road, University Town City, Fuzhou, Fujian, China
Kazuo Takahashi: Dept. of Civil Engineering, Faculty of Engineering, Nagasaki University, 1-14, Bunkyo-machi, Nagasaki, Japan
Baochun Chen: College of Civil Engineering, Fuzhou University, No. 2 Xueyuan Road, University Town City, Fuzhou, Fujian, China

Abstract
This study evaluates seismic performance of the school buildings with the selected template designs in Turkey considering nonlinear behavior of reinforced concrete components. Six school buildings
with template designs were selected to represent major percentage of school buildings in medium-size cities located in high seismic region of Turkey. Selection of template designed buildings and material properties were based on field investigation on government owned school buildings in several cities in western part of Turkey. Capacity curves of investigated buildings were determined by pushover analyses conducted in two principal directions. The inelastic dynamic characteristics were represented by equivalent single-degree-offreedom (SDOF) systems and their seismic displacement demands were calculated under selected ground motions. Seismic performance evaluation was carried out in accordance with recently published Turkish Earthquake Code that has similarities with FEMA-356 guidelines. Reasons of building damages in past earthquakes are examined using the results of performance assessment of investigated buildings. The effects of material quality on seismic performance of school buildings were investigated. The detailed examination
of capacity curves and performance evaluation identified deficiencies and possible solutions for template designs.

Key Words
Seismic performance evaluation; pushover analysis; reinforced concrete structure; school buildings.

Address
Mehmet Inel and Hayri Baytan Ozmen: Dept. of Civil Engineering, Pamukkale University, 20070 Denizli, Turkey
Huseyin Bilgin: Dept. of Civil Engineering, Epoka University, Rruga e Durresit, Tirana, Albania

Abstract
Having established the initial geometry and cable force of a typical three span suspension bridge under permanent load, the additional maximum response of the cable and the stiffening girder due to live load are determined, by means of an analytic procedure, considering the girder first hinged at its ends and then continuous through the main towers. The problem of interaction between the cable and the stiffening girder is examined taking under due consideration the second order effects, whereby, through the analogy to a fictitious tensioned beam under transverse load, a closed .form solution is achieved by means of a simple quadratic equation. It is found that the behavior of the whole system is governed by five simple dimensionless parameters which enable a quick determination of all the relevant design magnitudes of the bridge. Moreover, by introducing these parameters, a set of diagrams is presented, which enable the estimation of the influence of the geometric and loading data on the response and
permit its immediate evaluation for preliminary design purposes.

Key Words
suspension bridge; stiffening girder; static analysis; design.

Address
Leonidas T. Stavridis: Structural Engineering, National Technical University of Athens, Vas. Sofias 100-11528, Athens, Greece

Abstract
Laplace-Fourier transform techniques are used to investigate the interaction caused by mechanical, thermal and microstress sources in a generalized thermomicrostretch elastic medium with temperature-dependent mechanical properties. The modulus of elasticity is taken as a linear function of reference temperature. The integral transforms are inverted using a numerical technique to obtain the normal stress, tangential stress, tangential couple stress, microstress and temperature distribution. Effect of temperature dependent modulus of elasticity and thermal relaxation times have been depicted graphically on the resulting quantities. Comparisons are made with the results predicted by the theories of generalized thermoelasticity. Some particular cases are also deduced from the present investigation.

Key Words
Microstretch generalized thermoelastic solid, Integral transforms, Concentrated source, Microstress force

Address
Rajneesh Kumar and Rajani Rani Gupta: Dept. of Mathematics, Kurukshetra University, Kurukshetra-136 119, India

Abstract
This paper presents a new linearization algorithm to find the periodic solutions of the Duffing equation, under harmonic loads. Since the Duffing equation models a single degree of freedom system with a cubic nonlinear term in the restoring force, finding its periodic solutions using classical harmonic balance (HB) approach requires numerical integration. The algorithm developed in this paper replaces the integrals appearing in the classical HB method with triangular matrices that are evaluated algebraically. The computational cost of using increased number of frequency components in the matrixbased linearization approach is much smaller than its integration-based counterpart. The algorithm is computationally efficient; it only takes a few iterations within the region of convergence. An example comparing the results of the linearization algorithm with the ?exact? solutions from a 4th order Runge-Kutta method are presented. The accuracy and speed of the algorithm is compared to the classical HB method, and the limitations of the algorithm are discussed.

Key Words
duffing equation; harmonic balance method; nonlinear oscillator; linearization.

Address
Jale Tezcan and J. Kent Hsiao: Dept. of Civil & Environmental Engineering, Southern Illinois University, Carbondale, IL 62901, USA

Abstract
Three dimensional coupled bending-torsion dynamic vibrations of thin-walled open section beam subjected to moving vehicle are investigated by transfer matrix method. Through adopting the idea of Newmark-? method, the partial differential equations of structural vibration can be transformed to the differential equations. Then, those differential equations are solved by transfer matrix method. An iterative scheme is proposed to deal with the coupled bending-torsion terms in the governing vibration equations. The accuracy of the presented method is verified through two numerical examples. Finally, with different eccentricities of vehicle, the torsional vibration of thin-walled open section beam and vertical and rolling vibration of truck body are investigated. It can be concluded from the numerical results that the torsional vibration of beam and rolling vibration of vehicle increase with the eccentricity of vehicle. Moreover, it can be observed that the torsional vibration of thin-walled open section beam may have a significant nonlinear influence on vertical vibration of truck body.

Key Words
thin-walled beam; dynamic response; vehicle; transfer matrix method; Newmark-? method.

Address
Tianyu Xiang, Tengfei Xu, Xinpeng Yuan and Renda Zhao: Dept. of Bridge Engineering, Southwest Jiaotong University, Chengdu, 610031, P. R. China
Yuqiang Tong: China Highway Planning and Design Institute, Beijing, 100010, P. R. China

Abstract
This study presents the efficiency of simulating structural systems using a method that combines a simplified component model (SCM) and rigorous component model (RCM). To achieve a realistic simulation of structural systems, a numerical model must be adequately capturing the detailed behaviors of real systems at various scales. However, capturing all details represented within an entire structural system by very fine meshes is practically impossible due to technological limitations on computational engineering. Therefore, this research develops an approach to simulate large-scale structural systems that combines a simplified global model with multiple detailed component models adjusted to various scales. Each correlated multi-scale simulation model is linked to others using a multi-level hierarchical modeling simulation method. Simulations are performed using nonlinear finite element analysis. The proposed method is applied in an analysis of a simple reinforced concrete structure and the Reuipu Elementary School (an existing structure), with analysis results then compared to actual onsite observations. The proposed method obtained results very close to onsite observations, indicating the
efficiency of the proposed model in simulating structural system behavior.

Key Words
structural engineering; realistic simulation; multi-level hierarchical modeling; finite element analysis; simplified component model; rigorous component model.

Address
Hung-Ming Chen and Data Iranata: Dept. of Construction Engineering, National Taiwan University of Science and Technology, 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan

Abstract
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Key Words
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Address
Y. Z. Chen and X. Y. Lin: Division of Engineering Mechanics, Jiangsu University, Zhenjiang, Jiangsu, 212013 P.R. China


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