• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.753-760
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• 2006

This paper presents the procedure and results of the numerical modelling that was carried out to investigate the stability of reinforced soil slopes under dynamic railway load. The two-dimensional explicit dynamic finite element method (ABACUS) was used to carry out the numerical analyses. To simulate the railway load, the top surface of the embankment was excited by the uniform distributed load whose frequency and magnitude was estimated by the measured railway acceleration during train passing. The embankment displacements and geogrid axial forces were analyzed to evaluate the stability of reinforced soil slopes under the dynamic train load.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.6
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• pp.168-176
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• 1996

A diagnosis system which can monitor tool breakage and chipping in real time was developed using a DSP(Digital Signal Processor) board in face milling operation. AR modelling and band energy method were used to extract the feature of tool states from cutting force signals. Artificial neural network embedded on DSP board discriminates different patterns from features got after signal processing. The features extracted from AR modelling are more accurate for the malfunction of a process than those from band energy method, even though the computing speed of the former is slow. From the processed features, we can construct the real time diagnosis system which monitors malfunction by using a DSP board having a parallel processing capability.

• Journal of Convergence Society for SMB
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• v.4 no.2
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• pp.33-39
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• 2014

In this paper, basic backgrounds about capsule endoscopy are introduced, and the aims and objectives are also illustrated. Methodology and mathematical model for LuGre model were investigated to analyse system characteristics. A nonlinear friction model, the stick-slip motion system based on LuGre friction model was used to simulate the motion of capsule endoscopy inside human body. Under the different situation, LuGre friction model was simulated by Matlab Simulink software. The entire cycle of motion and the influence of parameters towards to velocity are fully simulated.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.3
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• pp.168-175
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• 1998

This study investigated the structural performance of the precast prestressed cylinder pipe having cracked under construction. The finite element formulation of PPC pipe incorporates Asoild elements using SAP90 program and the radial prestress force was transformed into the eqivalent external pressure. The analytical results were compared with the experimental results of full scale tests on PPC pipes subjected to static load. It is shown that the proposed modelling gives a realistic represention of the actual behavior. The analytical procedure is used to calculate the stresses in the PPC pipes and to check the crack opening under various situations such as bedding angle, earth pressure, and earth cover. Finally, the proposed modelling and analytical procedure should be especially usefull for the safety assessment of the PPC pipes under general loading conditions.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.3
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• pp.73-79
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• 2011

In this study, an analytical realization of end-milling system was introduced using recursive parametric modeling analysis. Also, the numerical mode analysis of end-milling system with different conditions was performed systematically. In this regard, a recursive least square modelling algorithm and the natural mode for real part and imaginary one was discussed. This recursive approach (RLSM) can be adopted for on-line end-milling identification. After experimental practice of the end-milling, the end-milling force was obtained and it was used for the calculation of FRF (Frequency response function) and mode analysis. Also the FRF was analysed for the prediction of a end-milling system using recursive algorithm.

• Computational Structural Engineering : An International Journal
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• v.1 no.1
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• pp.11-20
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• 2001

The paper describes the conceptual design, structural modelling and wind load analysis of tall buildings. The lateral stiffness of the building can be obtained economically through the interaction of core walls with peripheral frame tube and/or bundle of frame tubes and integrated design of the basement. The main structural components should be properly distributed such that the building will deflect mainly in the direction of the applied force without inducing significant response in other directions and twist. The cost effectiveness can be further enhanced through close consultation between architects and engineers at an early stage of conceptual design. Simplified structural modelling of the building and its response in three principal directions due to wind load are included. Effects of the two main structural components on the performances of a 70-story reinforced concrete building in terms of peak drift and maximum acceleration under wind load are discussed.

• Nuclear Engineering and Technology
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• v.55 no.3
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• pp.1152-1166
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• 2023

The bubbly flow of air or steam in subcooled water are investigated here in several test cases, characterized by different pipe sizes, bubble dimensions and flow rates, by means of CFD using a Eulerian-Eulerian approach. The performance of models that differ for the turbulence closure in the continuous phase, as well as for the description of the lift force on the dispersed phase, are compared in detail. When air is considered, the space of the experimental parameters leading to a reasonable performance for the selected models are identified and discussed, while the issues left in the modelling of the concurrent condensation are highlighted for the cases where steam is used.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.455-459
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• 1995

Catenary/pantograph system consists of overhead lines which have non-uniform elasticity and pantographs which move at high speed and give force to the lines, therefore happen to be failed in contacts between both from time to time. In this study, as the first step to develop a dynamic simulation program, the general theory is discussed for catenary/pantograph system and appropriate modelling. And comparison is conducted with the references after making a program which referred to the contact force equation algorithm. On this algorithm, the unknown contact force is computed by the equations which was induced as combining catenary and pantograph motion equations expressed in finite difference form. Another simulation program based on the assumed contact forces algorithm was developed. In this algorithm, numerical integraion of both the overhead line and pantograph equations, which without combining, are effected for two assumed values of contact force. The correct contact force is then obtained from these two sets of results by linear interpolation to satisfy the contact condition. Through the comparative review on the outputs from this program, it is verified that this algorithm is reliable.

• Earthquakes and Structures
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• v.6 no.4
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• pp.409-436
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• 2014

Although it is widely accepted that the interaction -between masonry infill and structural members significantly affects the seismic response of reinforced concrete (RC) frames, this interaction is generally neglected in current design-oriented seismic analyses of structures. Moreover, the role of masonry infill is expected to be even more relevant in the case of existing frames designed only for gravitational loads, as infill walls can significantly modify both lateral strength and stiffness. However, the additional contribution to both strength and stiffness is often coupled to a modification of the global collapse mechanisms possibly resulting in brittle failure modes, generally related to irregular distributions of masonry walls throughout the frame. As a matter of principle, accurate modelling of masonry infill should be at least carried out by adopting nonlinear 2D elements. However, several practice-oriented proposals are currently available for modelling masonry infill through equivalent (nonlinear) strut elements. The present paper firstly outlines some of the well-established models currently available in the scientific literature for modelling infill panels in seismic analyses of RC frames. Then, a parametric analysis is carried out in order to demonstrate the consequences of considering such models in nonlinear static and dynamic analyses of existing RC structures. Two bay-frames with two-, three- and four-storeys are considered for performing nonlinear analyses aimed at investigating some critical aspects of modelling masonry infill and their effects on the structural response. Particularly, sensitivity analyses about specific parameters involved in the definition of the equivalent strut models, such as the constitutive force-displacement law of the panel, are proposed.

• Structural Engineering and Mechanics
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• v.40 no.1
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• pp.29-48
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• 2011

Under large storm loads sections of a long pipeline on the seabed can be uplifted. Numerically this loss of contact is extremely difficult to simulate, but accounting for uplift and any subsequent recontact behaviour is a critical component in pipeline on-bottom stability analysis. A simple method numerically accounting for this uplift and reattachment, while utilising efficient force-resultant models, is provided in this paper. While force-resultant models use a plasticity framework to directly relate the resultant forces on a segment of pipe to the corresponding displacement, their historical development has concentrated on precisely modelling increasing capacity with penetration. In this paper, the emphasis is placed on the description of loss of penetration during uplifting, modelled by 'strain-softening' of the force-resultant yield surface. The proposed method employs uplift and reattachment criteria to determine the pipe uplift and recontact. The pipe node is allowed to become free, and therefore, the resistance to the applied hydrodynamic loads to be redistributed along the pipeline. Without these criteria, a localised failure will be produced and the numerical program will terminate due to singular stiffness matrix. The proposed approach is verified with geotechnical centrifuge results. To further demonstrate the practicability of the proposed method, a computational example of a 1245 m long pipeline subjected to a large storm in conditions typical of offshore North-West Australia is discussed.