• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.257-269
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• 2024

Purpose: The purpose of this study is to explain the pivotal role of the travel forecasting process in urban transportation planning. This study emphasizes the use of travel forecasting models to anticipate future traffic. Method: This study examines the methodology used in urban travel demand modeling within transportation planning, specifically focusing on the Urban Transportation Modeling System (UTMS). UTMS is designed to predict various aspects of urban transportation, including quantities, temporal patterns, origin-destination pairs, modal preferences, and optimal routes in metropolitan areas. By analyzing UTMS and its operational framework, this research aims to enhance an understanding of contemporary urban travel demand modeling practices and their implications for transportation planning and urban mobility management. Result: The result of this study provides a nuanced understanding of travel dynamics, emphasizing the influence of variables such as average income, household size, and vehicle ownership on travel patterns. Furthermore, the attraction model highlights specific areas of significance, elucidating the role of retail locations, non-retail areas, and other locales in shaping the observed dynamics of transportation. Conclusion: The study methodically addressed urban travel dynamics in a four-ward area, employing a comprehensive modeling approach involving trip generation, attraction, distribution, modal split, and assignment. The findings, such as the prevalence of motorbikes as the primary mode of transportation and the impact of adjusted traffic patterns on reduced travel times, offer valuable insights for urban planners and policymakers in optimizing transportation networks. These insights can inform strategic decisions to enhance efficiency and sustainability in urban mobility planning.

• Structural Engineering and Mechanics
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• v.28 no.1
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• pp.53-67
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• 2008

Anisotropic materials are increasingly required in modern technological applications. Certainly, civil, mechanical and naval engineers frequently deal with the situation of analyzing the dynamical behaviour of structural elements being composed of such materials. For example, panels of anisotropic materials must sometimes support electromechanical engines, and besides, holes are performed in them for operational reasons e.g., conduits, ducts or electrical connections. This study is concerned with the natural frequencies and normal modes of vibration of rectangular anisotropic plates supported by different combinations of the classical boundary conditions: clamped, simply - supported and free, and with additional complexities such holes of free boundaries and attached concentrated masses. A variational approach (the well known Ritz method) is used, where the displacement amplitude is approximated by a set of beam functions in each coordinate direction corresponding to the sides of the rectangular plate. Consequently each coordinate function satisfies the essential boundary conditions at the outer edge of the plate. The influence of the position and magnitude of both hole and mass, on the natural frequencies and modal shapes of vibration are studied for a generic anisotropic material. The classical Ritz method with beam functions as spatial approximation proved to be a suitable procedure to solve a problem of such analytical complexity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.4
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• pp.413-422
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• 2001

In this study, the effect of hydrodynamic masses is investigated in the dynamic characteristics and earthquake response analyses of the submerged HANARO flow tubes. First, the consistent hydrodynamic masses of the surrounding water are obtained by finite element method. Then, modal analyses and response spectrum analyses are performed and verified by comparing the results with those measured from an experiment. Arbitrary cross-sections of submerged structures and boundary conditions of the surrounding fluid can be considered by using the general benefits of a finite element method comparing with the conventional analytical methods. Practical criteria based on parametric studies are proposed to evaluate the dynamic characteristics of HANARO flow tubes including the hydrodynamic masses.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.950-967
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• 1995

Acoustic holography makes it possible to reconstruct the acoustic field based on the measurement of the pressure distribution on the hologram surface. Because of the merit that one can obtain an entire three-dimensional wave field from the data recorded on a two-dimensional surface, the holographic method has been widely studied. Being an experimental method, holography has an unavoidable error which is generate by sampling in space and frequency domain and finite aperture size. Its magnitude is dependent on the space and frequency domain and finite aperture size. Its magnitude is dependent on the shape of hologram surface, acoustic holography may be classified into four types of holography : rectangular type planeholography, circular type plane holography, cylindrical holography and spherical holography. In this paper, four types of holography are studied by modal summation method. Numerical simulation is performed using a monopole source with varying parameters to find out effects to the estimation error in each holography. Experiments of circular type plane holography and cylindrical holography explain strong relation between the shape of hologram surface and the acoustic field.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.3
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• pp.423-429
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• 1997

A simplified method for determining the mode components of the strain energy release rate of free-edge delaminations in laminated composite is proposed. The interlaminar stresses are evaluated as an interface moment and interface shear forces that are obtained from the equilibrium equations at the interface between the adjacent layers. Deformation of an edge-delaminated laminate is calculated by using a generalized quasi-three dimensional classical laminated plate theory developed by the authors. The analysis provides closed-form expression for the three components of the strain energy release rate. Comparison of results with a finite element solution using the virtual crack closure technique shows good agreement. In the present study, laminated composite with stacking sequences of [30/-30/90]$_{s}$ were examined. The simple nature of the method makes it suitable for primary design analysis for the delaminations of laminated composite.e.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.6
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• pp.1897-1907
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• 1991

An analysis is presented for the primary resonance of a clamped-hinged beam, which occurs when the frequency of excitation is near one of the natural frequencies, .omega.$_{n}$. Three mode interactions, .omega.$_{2}$=3.omega.$_{1}$, and .omega.$_{3}$=.omega.$_{1}$+2.omega.$_{2}$, are considered and their influence on the response is studied. The case of two mode interaction, .omega.$_{2}$=3.omega.$_{1}$, is also considered in order to compare it with the case of three mode interactions. The straight beam experiencing mid-plane stretching is governed by a nonlinear partial differential equation. By using Galerkin's method the governing equation is reduced to a system of nonautonomous nonlinear ordinary differential equations. The method of multiple scales is applied to obtain steady-state responses of the system. Results of numerical investions show that there exists no significant difference between both modal interactions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.591-596
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• 2006

This study is base on the fault detection and diagnosis when a crack is happened a structure. A crack in a structure will affect the modal parameters. We are searched a percentage of changes in the natural frequencies according to changes of location and propagation of the crack using the Rayleigh's energy method. This method is presented to identify the presence of a crack and its location. The study is carried out both theoretically and experimentally and the results are presented in this paper. The location of the crack is also moved from the fixed end to the free end along its length. The changes in natural frequencies are observed from theoretically study, due to the presence of the crack at different locations and depths, and the percentage change in frequency values are calculated. These results are confirmed by the experiments. And then, a difference between a cracked beam and uncracked beam observed using the bispectrum as high-order spectrum.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.914-920
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• 2002

Nonlinear flow-induced vibration characteristics of a generic missile wing (or control surface) are investigated in this study. The wing model has freeplay structural nonlinearity at its pitch axis. Nonlinear aerodynamic flows with unsteady shock waves are considered in the transonic flow region. To practically consider the effects of freeplay structural nonlinearity, the fictitious mass method (FMM) is applied to structural vibration analysis based on a finite element method (FEM). A computational fluid dynamics (CFD) technique is used for computing the nonlinear unsteady aerodynamics of all-movable wings. The aerodynamic analysis is based on the efficient transonic small-disturbance aerodynamic equations of motion using the potential-flow theory. To solve the nonlinear aeroelastic governing equations including the freeplay effect, a modal-based computational structural dynamic (CSD) analysis technique based on fictitious mass method (FMM) is used in time-domain. In addition, CSD and unsteady CFD techniques are simultaneously coupled to give accurate computational results. Various aeroelastic computations have been performed for a generic missile wing model. Linear and nonlinear aeroelastic computations have been conducted and the characteristics of flow-induced vibration are introduced.

• Wind and Structures
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• v.20 no.3
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• pp.363-388
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• 2015

For controlling the vibration of specific building structure with large span, a practical method for the design of MTMD was developed according to the characteristics of structures subjected to wind loads. Based on the model of analyzing wind-induced response of large-span structure with MTMD, the optimization method of multiple tuned mass dampers for large-span roof structures subjected to wind loads was established, in which the applicable requirements for strength and fatigue life of TMD spring were considered. According to the method, the controlled modes and placements of TMDs in MTMD were determined through the quantitative analysis on modal contribution to the wind-induced dynamic response of structure. To explore the characteristics of MTMD, the parametric analysis on the effects of mass ratio, damping ratio, central tuning frequency ratio and frequency range of MTMD, was performed in the study. Then the parameters of MTMD were optimized through genetic algorithm and the optimized MTMD showed good dynamic characteristics. The robustness of the optimized MTMD was also investigated.

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.709-717
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• 2017

This paper develops a two-stage method for structural damage identification by using modal data. First, the Residual Force Vector (RFV) is introduced to detect any potentially damaged elements of structures. Second, data of the frequency domain are used to build up the objective function, and then the Imperialist Competitive Algorithm (ICA) is utilized to estimate damaged extents. ICA is a heuristic algorithm with simple structure, which is easy to be implemented and it is effective to deal with high-dimension nonlinear optimization problem. The advantages of this present method are: (1) Calculation complexity can be decreased greatly after eliminating many intact elements in the first step. (2) Robustness, ICA ensures the robustness of the proposed method. Various damaged cases and different structures are investigated in numerical simulations. From these results, anyone can point out that the present algorithm is effective and robust for structural damage identification and is also better than many other heuristic algorithms.