• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.755-761
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• 2017

In railways powered by AC power, the main circuit breaker (MCB) is used for supplying the electric power to the catenary of the vehicle. Generally, the main circuit breaker is located between the pantograph and the main transformer, and the phase of the power applied to the vehicle changes according to the operation timing of the main circuit breaker. The operation of the main circuit breaker should be actively controlled according to the phase of the power source, since the phase of the power causes unintended transient states in the vehicle's electrical system in the form of an inrush current and surge voltage. However, the MCB has a delay time when it operates which is not constant. Therefore, an intelligent controller is needed to predict the operation delay time and control the opening and closing of the MCB.

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.7-13
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• 2014

Stiffness variations and wave propagation/reflection in railway catenaries are the primary sources of contact loss between a pantograph and a railway contact wire. This paper analyzes which design parameter is more important for 200km/h conventional rail and 300km/h high-speed rail, in order to effectively reduce the contact loss. For the high-speed rail, the wave propagation and reflection in the overhead contact lines are more influential than the stiffness variation over a span. When the high-speed rail needs to speed-up, it is necessary to develop higher strength contact wires in order to increase the wave propagation speed. In addition, the dropper clamp mass should be reduced in order to alleviate the wave reflection. However, it is noted that the increase in the tension to a messenger wire could deteriorate the current collection quality, which contrasts with expectations. For the 200km/h conventional rail, the stiffness variation over a span is more influential than the wave propagation and reflection. Therefore, shortening span length, increasing the tension in the contact wire and optimizing the location of the droppers are recommended for a smoother stiffness variation over the span.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.1 no.1
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• pp.93-101
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• 1989

A geometrically nonlinear cable finite element is presented to use in the static or dynamic modeling of offshore and onshore structures such as guyed tower, tension leg platform or mooring buoy, submarine cable, cable-stayed bridge, suspension bridge, cable roof and so on. The cable finite element is derived directly from the compatibility equations and flexibility matrix of elastic catenary cable theory for the arbitary plane loading and geome try. A general and virsatile computer program has been developed to perform the analyses of cable member itself or cable guyed or suspened structures, in which Newmark-$\beta$ method is used to obtain a time domain solution and Newton-Raphson iteration method is used to solve the nonlinear system of compatibility equations of cable and algebraic static or dynamic equations at each time step. The results from the static and dynamic analysis of a cable member by the computer program are summarized and presented.

• Journal of the Korean Society for Railway
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• v.12 no.5
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• pp.732-737
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• 2009

Wind tunnel testing on the real-scale pantograph for high-speed train has been conducted to investigate the aerodynamic characteristic of the pantograph at high-speed. The mid-scale subsonic wind tunnel of Korea Airforce Acamedy with 3.5m width, 2.45m height, and 8.8m length test section has been employed. The test model has been supported above 50cm height from the bottom of test section using vertical strut to eliminate the boundary layer generated from the bottom of the test section. The height of the pantograph has been varied in three cases, in both of the normal running and reverse running modes. The resultant lift forces of the pantograph to catenary system in all the cases have been measured and the relation between the test conditions and the lift forces have been extensively analyzed.

• Journal of the Korean Geotechnical Society
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• v.29 no.11
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• pp.85-97
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• 2013

Electric pole foundations for overhead catenary system of railroad should be designed so that they may resist significant overturning moment but relatively small vertical forces. Also they should have proper shapes to be installed at restricted narrow areas adjacent to railroad track. In this paper the moment responses of rectangular pole foundations according to their shapes were investigated numerically. A three-dimensional finite element method was developed and verified so that the numerical behaviors of the foundation resisting the overturning moments were compared reasonably well with those from an existing real-scale load test. The influences of aspect ratio, varying section with depth and loading directions for rectangular section were investigated using the developed numerical method. From the numerical results, the optimized shapes of pole foundation for more effective and economic installation adjacent to railroad track are proposed.

• Proceedings of the KIEE Conference
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• 1998.07c
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• pp.1166-1169
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• 1998

The Load characteristic of electric railway requires the power demand of the high capacity which amplitude is spacial-temporally fluctuated due to frequent starting and stopping with large tractive force. The conventional electric railway mainly consists of the resistance controlled and the thyristor controlled locomotives, are compensated for their bad characteristics of the power factor$(70\sim80%)$ with installation of another capacitor improving power factor at the substation. Since 1994, VVVF train car with good characteristics of power factor(100%) have been introduced and operated in Kwa-Chon Line. From the present technical tendency, it is judged that introduction of the locomotive with various controlled methods is necessary. The protective equipments installed at the substation are complicated and various aspects to detect faults and reduce their extension, so the universal countermeasures are required. Specially in the case of the fault occurrence it is difficult to calculate the fault location because of the change in the contactline constant according to modifying the characteristics of the contactline (the dualized catenary wire and extension, etc), so much time is required for the detection of fault location. In BT-fed method distance-relays and fault-locators are not installed, we have so many difficulties in the quick accident recovery.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.540-545
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• 2007

The tilting train is able to tilt its body towards the center of the turning radius, preventing roll-over of the train as it runs on a curved rail at high-speed. This train, widely accepted for commercial purpose internationally, is very beneficial in that the operating time is shortened without much capital investment to the infrastructure where there are many curved rails. Over several years, the Korea Railroad Research Institute (KRRI) has developed such a train. In this paper, the safety of the Korean tilting train express (TTX) is investigated using a dynamic simulation model. Since proper safety standards have not been established for the TTX, those for the Korean train express (KTX) is employed to analyze the safety and ride comfort of the TTX. This study is useful in predicting the behavior of the TTX and ride comfort, and conforms that designed TTX is stable enough to satisfy the safety standards. It would be useful to recommend proper normal operating speed and determine the maximum safety speed, according to the result. Furthermore, it would be possible to provide basic reference data when analyzing the dynamic effect of the catenary system and the fatigue of the bogie.

• International Journal of High-Rise Buildings
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• v.7 no.4
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• pp.375-387
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• 2018

This paper presents a review on progressive collapse mechanism of steel framed buildings exposed to fire. The influence of load ratios, strength of structural members (beam, column, slab, connection), fire scenarios, bracing systems, fire protections on the collapse mode and collapse time of structures is comprehensively reviewed. It is found that the key influencing factors include load ratio, fire scenario, bracing layout and fire protection. The application of strong beams, high load ratios, multi-compartment fires will lead to global downward collapse which is undesirable. The catenary action in beams and tensile membrane action in slabs contribute to the enhancement of structural collapse resistance, leading to a ductile collapse mechanism. It is recommended to increase the reinforcement ratio in the sagging and hogging region of slabs to not only enhance the tensile membrane action in the slab, but to prevent the failure of beam-to-column connections. It is also found that a frame may collapse in the cooling phase of compartment fires or under travelling fires. This is because that the steel members may experience maximum temperatures and maximum displacements under these two fire scenarios. An edge bay fire is more prone to induce the collapse of structures than a central bay fire. The progressive collapse of buildings can be effectively prevented by using bracing systems and fire protections. A combination of horizontal and vertical bracing systems as well as increasing the strength and stiffness of bracing members is recommended to enhance the collapse resistance. A protected frame dose not collapse immediately after the local failure but experiences a relatively long withstanding period of at least 60 mins. It is suggested to use three-dimensional models for accurate predictions of whether, when and how a structure collapses under various fire scenarios.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.58 no.3
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• pp.230-240
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• 2022

In general, a high tension on the anchor and chain is placed when a ship at anchor is subjected to heavy weather. Mariners have to pay attention to whether dragging anchor occurs to keep the safety of the ship at anchorage since it is difficult to maintain the stable motion of ship and it causes collisions with other ships nearby. In this paper, the ship motion against the external forces was shown to obtain the fundamental data about characteristic of holding power due to nature of seabed at anchor, so practical trials were carried out in rocky area and muddy area using a trial ship around coastal area of South Korea. In muddy seabed, holding power showed reasonable tension values depending on the distance from anchor position of continuing swing motions of a ship corresponding to wind force. Meanwhile in rocky seabed, tension values on the chain appeared very high occasionally regardless of the distance from the anchor position and seemed to exceed its holding power to be the breaking strain of the chain although weather was not in a severe condition. Therefore, some of the cables laid on the seabed were presumed to be caught in a crack on the rock. It is assumed that even a small amount of external force may cause the chain to break in a moment in rocky seabed. Additionally, wind and current forces had a somewhat contradictory effect on holding power of the ship between them.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.692-700
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• 2007

A trial run of locally-developed tilting train has been in process on Chungbuk line since the test vehicle was first produced. For the system stabilization, interface verification among the systems including track, structure, catenary and signaling system, not to mention the rolling stock, is very crucial. In the area of wayside structure, the stability of track structure and train run shall be evaluated through the review of impact by increased speed by developed train on track structure. The study thus was intended to evaluate the impact on track while a tilting train is running the curve section, which is vulnerable to accelerated train speed. The analysis of tilting train test running the part of Chungbuk line and Honam line was conducted to identify the impact on existing track performance by tilting train. To identify the movement behavior of each part of track while tilting train, high speed train and traditional train (Mugunghwa and freight train) were running the existing line, wheel load, lateral wheel load, rail bending stress, vertical and lateral displacement of rail and vertical displacement of sleeper were compared and analyzed so as to evaluate the expected impact by tilting train for improving the train speed.