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CONTENTS
Volume 33, Number 5, November30 2009
 

Abstract
The rotating Rayleigh-Timoshenko beam element based on B-spline wavelet on the interval (BSWI) is constructed to discrete short shaft and stiffness disc. The crack is represented by nondimensional linear spring using linear fracture mechanics theory. The wavelet-based finite element model of rotor system is constructed to solve the first three natural frequencies functions of normalized crack location and depth. The normalized crack location, normalized crack depth and the first three natural frequencies are then employed as the training samples to achieve the neural networks for crack diagnosis. Measured natural frequencies are served as inputs of the trained neural networks and the normalized crack location and depth can be identified. The experimental results of fatigue crack in short shaft is also given.

Key Words
short shaft; wavelet-based element; neural networks; crack identification.

Address
Jiawei Xiang: School of Mechantronic Engineering, Guilin University of Electronic Technology, Guilin, 541004, P.R. China, State Key Laboratory for Manufacturing Systems Engineering (Xi

Abstract
Nowadays, Eurocodes have become the reference standards for silo design within the European Union. They include new procedures for load assessment and structural verifications aiming to design safer silos. However, many silo manufacturers are still reluctant to use them (or at least all their prescriptions) because of the loss of competitiveness they are experiencing in comparison with former standards. This paper shows how steel cost of flat-bottomed circular silos varies when different silo geometries and stored materials are considered. The influence of critical structural verifications on steel costs, such as buckling of the silo wall, were also analyzed and some conclusions and practical recommendations for silo designers were proposed.

Key Words
Eurocodes; silo; costs; steel; buckling.

Address
Carlos Gonzalez-Montellano, Alvaro Ramirez, Eutiquio Gallego and Francisco Ayuga: BIPREE Research Group (Buildings, Infrastructures and Projects for Rural and Environmental Engineering), Universidad Politecnica de Madrid. Avda. Complutense S/N, 28040 Madrid. Spain

Abstract
In this paper a four-node hybrid stress element is proposed for analysing arbitrarily shaped plates on a two parameter elastic foundation. The element is developed by combining a hybrid plate stress element and a soil element. The formulation is based on Hellinger-Reissner variational principle in which both inter element compatible boundary displacement and equilibrated stress fields for the plate as well as the foundation are chosen separately. This formulation also allows a low order polynomial interpolation functions. Numerical examples are presented to show that the validity and efficiency of the present element for the plate analysis resting on an elastic foundation. In these examples the effect of soil depth, interaction between closed plates on soil parameters, comparison with Winkler hypothesis is investigated.

Key Words
plate; elastic foundation; assumed stress hybrid formulation; finite element.

Address
Kutlu Darilmaz: Department of Civil Engineering, Istanbul Technical University 34469, Maslak, Istanbul, Turkey

Abstract
In the field of predicting structural safety and reliability the operating conditions play an essential role. Since the time and cost limitations are a significant factors in engineering it is important to predict the future operating conditions as close to the actual state as possible from small amount of available data. Because of the randomness of the environment the shape of measured load spectra can vary considerably and therefore simple distribution functions are frequently not sufficient for their modelling. Thus mixed distribution functions have to be used. In general their major weakness is the complicated calculation of unknown parameters. The scope of the paper is to investigate the load spectra growth for actual operating conditions and to investigate the modelling and extrapolation of load spectra with algorithm for mixed distribution estimation, REBMIX. The data obtained from the measurements of wheel forces and the braking moment on proving ground is used to generate load spectra.

Key Words
load spectra growth; extrapolation; reliability; mixed distribution function; alternative algorithm.

Address
Matej Volk, Matija Fajdiga and Marko Nagode: University of Ljubljana, Faculty of Mechanical Engineering, A

Abstract
This paper presents the details of finite element (FE) modeling and analysis of an external prestressing technique to strengthen a prestressed concrete (PSC) end block. Various methods of external prestressing techniques have been discussed. In the proposed technique, transfer of external force is in shear mode on the end block creating a complex stress distribution. The proposed technique is useful when the ends of the PSC girders are not accessible. Finite element modeling issues have been outlined. Brief description about material nonlinearity including key aspects in modeling inelastic behaviour has been provided. Finite element (FE) modeling including material, loading has been explained in depth. FE analysis for linear and nonlinear static analysis has been conducted for varying external loadings. Various responses such as out-of-plane deformation and slip have been computed and compared with the corresponding experimental observations. From the study, it has been observed that the computed slope and slip of the steel bracket under external loading is in good agreement with the corresponding experimental observations.

Key Words
concrete; external prestressing; finite element analysis; material nonlinearity.

Address
A. Rama Chandra Murthy, S. Chitra Ganapathi, S. Saibabu, N. Lakshmanan and R. Jayaraman: Structural Engineering Research Centre, CSIR, CSIR Campus, Taramani, Chennai, India-600 113
R. Senthil: Structural Engineering Department, Anna University, Chennai,India-600 025

Abstract
In this paper we compare the solution of the one-dimensional beam model and the numerical solution of the two-dimensional linearized elasticity problem for rectangular domain of the beam-like form. We first derive the beam model starting from the two-dimensional linearized elasticity, the same way it is derived from the three-dimensional linearized elasticity. Then we present the numerical solution of the two-dimensional problem by finite element method. As expected the difference of two approximations becomes smaller as the thickness of the beam tends to zero. We then analyze the applicability of the one-dimensional model and verify the main properties of the beam modeling for thin beams.

Key Words
linearized elasticity; asymptotic expansion; beam model; numerical solution; finite elements.

Address
Eva Fabijanic: Pliva d.d.,10000 Zagreb, Croatia
Josip Tambaca: Depat. of Mathematics, University of Zagreb, Bijenicka 30,10000 Zagreb, Croatia

Abstract
For the calculation of foundation settlement it is recommended to take into account so called influence zone inside the subsoil bellow the foundation structure. Influence zone inside the subsoil is the region where the load has a substantial influence on the deformation of the soil skeleton. The soil skeleton is pre-consolidated or over consolidated due to the original geostatic stress state. An excavation changes the original geostatic stress state and it creates the space for the load transferred from upper structure. The theory of elastic layer in Westergard manner is selected for the vertical stress calculation. The depth of influence zone is calculated from the equality of the original geostatic stress and the new geostatic stress due to excavation combined with the vertical stress from the upper structure. Two close formulas are presented for the influence zone calculation. Using ADINA code we carried out several numerical examples to verify the proposed analytical formulas and to enhance their use in civil engineering practice. Otherwise, the FEM code accuracy can be control.

Key Words
pre-consolidation pressure; influence zone; Kantorovich method; fundamental solution layered subsoil; geostatic stress state; FEM.

Address
Pavel Kuklik: Faculty of Civil Engineering, Czech Technical University in Prague, Czech Republic
Miroslav Broucek: Faculty of Civil Engineering, Czech Technical University in Prague, Czech Republic
Marie Kopackova: Faculty of Civil Engineering, Czech Technical University in Prague, Czech Republic

Abstract
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Key Words
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Address
M.Z. Kabir and R. Vasheghani-Farahani: Dept. of Civil and Environmental Engineering, Amirkabir University of Technology, Iran

Abstract
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Key Words
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Address
Guojun Zhang: College of Architecture Engineering, Shanghai Normal University, Shanghai 201418, China
Boquan Liu: School of Civil Engineering, Chang\'an University, Xi\'an 710061, China
Guoliang Bai: College of Civil Engineering, Xi\'an University of Architecture and Technology, Xi\'an 710055, China
Jianxin Liu: College of Architecture Engineering, Shanghai Normal University, Shanghai 201418, China


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