Abstract in English:High speed maglev is one of the most important reformations in the ground transportation systems because of its no physical contact nature. This paper intends to study the dynamic response of the single-span guideway induced by moving maglev train. The dynamic model of the maglev train-guideway system is established. In this model, a maglev train consists of three vehicles and each vehicle is regarded as a multibody system with 34 degrees-of-freedom. The guideway is modeled as a simply supported beam. Considering the motion-dependent nature of electromagnetic forces in the maglev system, an iterative approach is presented to compute the dynamic response of a maglev train-guideway system. The histories of the train traversing the guideways are simulated and the dynamic responses of the guideway and the train vehicles are calculated. A field experiment is carried out to verify the results of the analysis. The resonant conditions of single-span guideway are analyzed. The results show that all the dynamic indexes of train-guideway system are far less than permissive values of railway and maglev system, the vertical resonant of guideways caused by periodical excitations of the train will not happen.
Abstract in English:In this paper a trigonometric shear deformation theory is presented for the free vibration of thick orthotropic square and rectangular plates. In this displacement based theory the in-plane displacement field uses sinusoidal function in terms of thickness coordinate to include the shear deformation effect. The cosine function in terms of thickness coordinate is used in transverse displacement to include the effect of transverse normal strain. The most important feature of the theory is that the transverse shear stress can be obtained directly from the constitutive relations satisfying the shear stress free surface conditions on the top and bottom surfaces of the plate. Hence the theory obviates the need of shear correction factor. Governing equations and boundary conditions of the theory are obtained using the principle of virtual work. Results obtained for frequency of bending mode, shear mode and thickness stretch mode of free vibration of simply supported orthotropic square and rectangular plates are compared with those of other refined theories and exact solution from theory of elasticity wherever applicable.
Abstract in English:In this paper, free vibration of functionally graded nonuniform straight-sided plates with circular and non-circular cutouts has been investigated. Moreover, thermal effects on free vibration analysis and the effects of various parameters on natural frequencies of these plates were evaluated. The material properties were assumed to be graded across thickness, which vary according to the linear distribution law. The investigated parameters in this study are: (1) cutout size (2) type of loading (3) different boundary conditions. It should be mentioned that the obtained results of thermal effect on free vibration of the FG nonuniform straight-sided plates (such as skew and trapezoidal plates) with cutouts have not been studied yet. Therefore, the results of this investigation can be implemented in future studies.
Abstract in English:This work presents a hybrid experimental theoretical technique for residual stresses analysis of mechanical components. It was used the blind hole technique along with the Electronic Speckle Pattern Interferometry (ESPI) method and Airy stress functions for the determination of the principal stress components. Displacement information is fitted in order to extract Airy stress function coefficients. The results demonstrate that this technique is of great utility to determine the average principal stress and local stress gradients.
Abstract in English:This paper describes an extended formulation for the coupled beam method (CBM). The method is originally developed for elastic bending response analysis of passenger ships with large multi-deck superstructures. The extension is mainly performed to enable the available method in order to study elastic bending behaviour of ships fitted with superstructures of any sizes and locations. Finite element method (FEM) is applied for solving the equilibrium equations. Both hull and superstructure of the ship are modelled using beam elements. The connection between beam elements representing hull and superstructure is made using specially developed spring box elements. The accuracy of the extended method is demonstrated using an available experimental result. Then, two simplified structures, one representing a ship with a short superstructure and the other one representing a ship with a long superstructure, are analysed in order to validate the extended coupled beam method against the finite element method. In spite of some existing simplifications in the extended formulation, it is very effective in the early stages of ship structural design owing to its advantageous capability of rapid estimation of the longitudinal stress distributions along the height of ships at different stations.
Abstract in English:This paper presents a probabilistic capacity spectrum strategy for the reliability analysis of a bridge pile shaft, accounting for uncertainties in design factors in the analysis and the soil-structure interaction (SSI). Monte Carlo simulation method (MCS) is adopted to determine the probabilities of failure by comparing the responses with defined limit states. The analysis considers the soil structure interaction together with the probabilistic application of the capacity spectrum method for different types of limit states. A cast-in-drilledhole (CIDH) extended reinforced concrete pile shaft of a bridge is analysed using the proposed strategy. The results of the analysis show that the SSI can lead to increase or decrease of the structure's probability of failure depending on the definition of the limit states.
Abstract in English:In this research, finite element and boundary element methods are coupled together to model the interaction of a piezoelectric ceramic working as an actuator with an elastic material. Piezoelectric-elastic material's interaction occurs in smart structures. This work is aimed at determining the actuation effects being transferred from the actuators to the host and the resulting overall structural response. To obtain the amount of these actuations, the system of the host structure and an actuator has been modeled by using coupled finite element boundary element method in frequency domain. The host structure, which is assumed as an isotropic elastic solid region is modeled as a half space. The piezoelectric ceramic region is modeled by the 3-D finite element method, while the elastic half space with boundary element method. Finite element model of piezoelectric ceramic and boundary element model of the elastic half space are coupled together at their interface such that the vibrations of the piezo-actuator induce vibrations in the elastic half space. A couple of examples are given to show the induced displacement field around the piezo-actuator on the surface of the elastic medium. The results show that high jump in magnitude of horizontal displacements at the corners of the actuator attached to the structure occurs, which is an indication of high stress concentration, of the shear stress type at the corners. This stress concentration sometimes causes complete debonding of the actuator from the base structure. By using the suggested BEM-FEM coupled model for actuators with different dimensions or material properties much useful information concerning the amount of actuation and load transfer can be obtained. The presented work is a step towards modeling of structural health monitoring systems.
Abstract in English:This paper presents an approach for the global optimization of truss sizing and geometry that is based on a probabilistic restart procedure coupled with a local search algorithm. The resulting algorithm is able to guarantee local optimality and provides a set of local optima which contain, with an increasing probability as the number of restarts increases, the global solution. The optimization problem searches for a truss structure of minimum volume, subject to stress constraints. The design variables are the bars cross-section areas and some nodal coordinates. Several loading conditions are also considered. Finally, four numerical examples are presented and the main aspects of the approach are discussed.
Abstract in English:This paper aims to measure natural frequencies of Profiled Steel Sheet Dry Board (PSSDB) with Concrete infill (PSSDBC) system. For this purpose, experimental tests by estimation of Frequency Response Function (FRF) and a numerical method by development of Finite Element Model (FEM) are used. The connection stiffness between Peva45 as Profiled Steel Sheet (PSS) and different concrete grades of 25 (C25), 30 (C30), and 35 (C35) are measured by push-out tests to be used in the FEM. The effect of presence of concrete in the PSSDB system on the natural frequencies such as Fundamental Natural Frequency (FNF) of the system is investigated. The variability in the FNF of the studied system under different parameters such as concrete grades, thicknesses of PSS and Dry Board (DB), and boundary conditions is determined. In a wide numerical study, the FNF of the PSSDBC system with practical dimensions is revealed for different lengths, widths, and boundary conditions. The results help designer predict serviceability and design criteria of the studied panels.