• Structural Engineering and Mechanics
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• v.59 no.3
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• pp.403-430
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• 2016

This paper studies the dynamics of the lineal-located time-harmonic moving-with-constant-velocity load which acts on the hydro-elastic system consisting of the elastic plate, compressible viscous fluid - strip and rigid wall. The plane-strain state in the plate is considered and its motion is described by employing the exact equations of elastodynamics but the plane-parallel flow of the fluid is described by the linearized Navier-Stokes equations. It is assumed that the velocity and force vectors of the constituents are continuous on the contact plane between the plate and fluid, and impermeability conditions on the rigid wall are satisfied. Numerical results on the velocity and stress distributions on the interface plane are presented and discussed and the focus is on the influence of the effect caused by the interaction between oscillation and moving of the external load. During these discussions, the corresponding earlier results by the authors are used which were obtained in the cases where, on the system under consideration, only the oscillating or moving load acts. In particular, it is established that the magnitude of the aforementioned interaction depends significantly on the vibration phase of the system.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.493-499
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• 2003

Railroad, a superior mode of public transportation provides safe, efficient, speedy, comfortable and economical service, has fundamentally different characteristics from airplanes, ships and cars. Among the unique characteristics of a railroad is the fact that it operates on fixed track with multiple car trains. The subway system was first selected as the best solution to difficult automobile traffic conditions and environmental problems. Seoul subway no.1line (Jongno line) was opened for service on August 15, 1974. Seoul city has completed and now operates eight subway lines (286.7km) since 1974. At present the subways operate in Busan, Daegu and Incheon city, and are under construction in Gwangju and Daejeon city. The power source for subway trains has been electricity since 1896, and power supply systems are the third rail type and/or the catenary system. The typical catenary system is the rigid bar type. R-bar and T-bar are used in the rigid bar type of catenary system, and the two types of R-bar and T-bar are uesd in Korea also. R-bar is used only for AC 25kV power supply and T-bar for DC 1,500V. From 30 years of subway experience I would like to suggest the most economic catenary system to ensure of safety, reliability and expediency for the railway lines to be constructed and the forthcoming replacement due to the life cycle after studying and analysing the characteristics, advantages and disadvantages of R-bar and T-bar.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2467-2474
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• 1993

This paper deals with the cantilever subjected to a follower force which is generated by real rocket motor which has linearly decreasing thrust. The cantilever is assumed to be uniform and elastic one, In the theoretical analysis, the tip mass of rocket motor is considered as a rigid body and effects of its dynamic parameters are shown and compared with the experimental results. Particularly, the variation of the 2nd natural frequency due to the decreasing thrust is measured in the experiments and compared with the theoretical estimations. Approximate method is adopted in the theoretical analysis using Galerkin method by introducing 3-element modified operator and modified variable which represent eqation of motion and natural boundary conditions. In general, structural damping effects can be neglected and all the rigid body parameters must be taken into account in case of the short action time of the follower force and the relatively big tip mass like the system of this paper according to the experiment. Good agreement was obtained between the theoretical estimations and the experimental results by neglecting structural damping and considering all the rigid bidy parameters of the tip mass.

• Structural Engineering and Mechanics
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• v.61 no.5
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• pp.645-655
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• 2017

To determine the seismic applicability of a long-span railway concrete upper-deck arch bridge with concrete-filled steel-tube (CFST) rigid skeleton ribs, some fundamental principles and seismic approaches for long-span bridges are investigated to update the design methods in the current Code for Seismic Design of Railway Engineering of China. Ductile and mixed isolation design are investigated respectively to compare the structural seismic performances. The flexural moment and plastic rotation demands and capacities are quantified to assess the seismic status of the ductile components. A kind of triple friction pendulum (TFP) system and lead-plug rubber bearing are applied simultaneously to regularize the structural seismic demands. The numerical analysis shows that the current ductile layout with continuous rigid frame approaching spans should be strengthened to satisfy the demands of rare earthquakes. However, the mixed isolation design embodies excellent seismic performances for the continuous girder approaching span of this railway arch bridge.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.707-716
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• 2006

The optimization of the direct design system of semi-rigid steel frames using advanced analysis and genetic algorithm was presented. Advanced analysis can predict the combined nonlinear effects of connection, geometry, and material on the behavior and strength of semi-rigid frames. Geometric nonlinearity was determined using stability functions. On the other hand, material nonlinearity was determined using the Column Research Council (CRC) tangent modulus and parabolic function. The Kishi-Chen power model was used to describe the nonlinear behavior of semi-rigid connections. The genetic algorithm was used as the optimization technique. The objective function was assumed as the weight of the steel frame, with the constraint functions accounting for load-carrying capacities, deflections, inter-story drifts and ductility requirement. Member sizes determined by the proposed method were compared with those derived using the conventional method.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.2
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• pp.20-24
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• 2010

High speed cutting processes of rigid flexible printed circuit board by making use of high power UV laser with nano-second pulse width have been proposed and investigated experimentally. Also robust laser cutting system has been designed and developed in order to obtain a good cutting quality of rigid and flexible PCB with multi-layers (2-6 layers). Power controller module developed for ourselves is adapted to control the laser output power in the range less than 1%. The systems show the good performance of cutting speed, cutting width and cutting accuracy, respectively. Especially we have confirmed that the short circuit problem due to the carbonized contamination occurred in cross section of multi-layers by thermal effect of high power laser has been improved largely by using multi-pass cutting process with low power and high speed.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.37-44
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• 2013

This study is about the connector of the floating platform in order to ensure safety due to various climate changes. The purpose of this study is to recommend the connector model of floating platform based on concrete structures after reviewing the literatures related in establishing floating structure in case of various climate changes in domestic coast. This study introduces the concept generation, existing model, detailed design and evaluation including current and future development of the technologies of marina floating platform connector based on concrete structures. The results from the research show that the analysed connector design (Rigid Pontoon Connector) provides a highly efficient and practical solution to facilitate connection of stable floating platform.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.1
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• pp.1-8
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• 2019

The optimal design parameters of a dynamic absorber (DA) in a machine body (that is considered as a rigid body) are discussed in this paper. The bounce and rotation motions of the rigid body have been controlled passively by a DA, which consists of a mass and a spring. The rigid body is subjected to a harmonically excited force and supported by linear springs at both ends. To define the motion of a rigid body with a DA, the equation of motion was expressed in the third-order matrix form. To define the optimal design conditions of a DA, the reduction of dynamic characteristics, represented by the amplitudes of bounce and rotation, and the transmitted powers, were evaluated and discussed. The level of reduction was found to be highly dependent on the location and spring stiffness of the DA.

• Structural Engineering and Mechanics
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• v.2 no.4
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• pp.327-343
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• 1994

This is the second part of the paper (Rojek and Kleiber 1993) devoted to nonlinear dynamic analysis of structures consisting of rigid and deformable parts. The first part contains a theoretical formulation of nonlinear equations of motion for the coupled system as well as a solution algorithm. The second part presents the computer implementation of the equations derived in the first part with a short review of the capabilities of the computer program used and the library of finite elements. Details of material nonlinearity treatment are also given. The paper is illustrated by discussing a practical problem of a safety cab analysis for an agricultural tractor.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.295-302
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• 1999

This paper is the experimental and analytic of reinforced concrete hemisphere dome under vertical load. It is described that when the reinforced concrete hemispherical dome supported on cylindrical wall is loaded vertically, how the opening part of dome will behave mechanically The experimental and analytic model is a Hemispherical dome with opening and the meridian angle of opening is 76$^{\circ}$at the center of sphere under concentrated load around the opening, but this is reinforced by a ring is sufficient stiffness. The diagrams of crack development are represented to understand the behavior of the reinforced concrete hemispherical dome. The method of crack analysis will be applied the rigid element spring model. The rigid element spring model is a new discrete element analysis, each divided element is assumed by rigid elements without deformation which is interconnected with elasto-plastic spring system.