• Proceedings of the KSR Conference
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• 2003.05a
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• pp.68-81
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• 2003

Rockfall protection fence is one of the most common rockfall protection methods in Korea. If rockfall protection fences are required along the road or railway, their location, height and capacity, in terms of the maximum kinetic energy that they can absorb, should be specified. Within this paper, the best practice of rockfall barrier is introduced. Modern rockfall simulations as a means to define risks, protection requirements, dynamic loading and height of potential structures and selection of appropriate placement is presented. Technical possibilities of rockfall barriers and their actual limits are presented. Safety concepts based on probabilities approaches are proposed. Recent studies performed in other countries show that Flexible Barriers are also a feasible system to stop and retain debris flows. Finally an outlook onto further development is given.

• Journal of the Korean Society for Railway
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• v.10 no.4
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• pp.444-450
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• 2007

The bi-modal tram guided by the magnetic guidance system has two car-bodies and three axles. Each axle of the vehicle has an independent suspension to lower the floor of the car and improve ride quality. The turning radius of the vehicle may increase as a consequence of the long wheel base. Therefore, the vehicle is equipped with the All-Wheel-Steering(AWS) system for safe driving on a curved road. Front and rear axles should be steered in opposite directions, which means a negative mode, to minimize the turning radius. On the other hand, they also should be steered in the same direction, which means a positive mode, for the stopping mode. Moreover, only the front axle is steered for stability of the vehicle upon high-speed driving. In summary, steering angles and directions of the each axle should be changed according to the driving environment and steering mode. This paper proposes an appropriate AWS control algorithm for stable driving of the bi-modal tram. Furthermore, a multi-body model of the vehicle is simulated to verify the suitability of the algorithm. This model can also analyze the different dynamic characteristics between 2WS and AWS.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.830-835
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• 2011

DMT Freight is judged that economic performance is good because can increase cargoes than existing freight. However, the existing freight cars, each with a different balance to the body structure is bogie because the vibrations may occur. Thus, by minimizing vibration over the existing freight securing the safety of the driving if you will not have major problems in cargoes. In this study, multi-body dynamic analysis tool, VI-Rail using the actually Gyeongbu Railroad line and an empty, full freight condition include curve radius, track irregularity, cent. DMT freight of the derailed wagons were assessed for safety analysis. Full and empty freight conditions for parity in the Gyeongbu Railroad line(Dongdaegoo ${\leftrightarrow}$Gyungsan) derailment safety analysis, such as derailment safety coefficient and the radius wheel road decrement, echoing the curve and the orbit is affected by the irregularity was found. Full freight condition than the empty conditions showed a significant derailment safety. Overall, the limits of derailment coefficient (Q/P=0.8) and wheel road decrement limits (${\Delta}P/P=0.6$) is less safe with me confirmed that the derailment safety.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1736-1746
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• 2008

Because present road traffic reaches to the limitation of its faculty, Korean tilting train was developed to find the solution by increasing the speed of rail road. A tilting train can run on a curved rail at high speed so it improves a speed of a rail transit without constructing a new line. Only minimum modification is necessary for a existing line. According to above requirement, Korean tilting train was developed in 2007 and the try run has been executing since April, 2007 in order to validate its safety and reliability in a service lines. And this test and estimation will be completed in 2009. After completing a try run, main parts of tilting train will be studied again to commercialize and localize including a bogie and its commercial model design will be finalized by 2012. In order to achieve the development target as mentioned above, the study have been done to improve the bogie system. As the first step to design commercialized bogie system, measurements from the try run and a dynamic analysis were used to find problems of present bogie system well. So this project is performed to decide what parts of the bogie should be modified in basis of this result.

• Structural Monitoring and Maintenance
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• v.5 no.4
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• pp.463-488
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• 2018

In the last decades, research efforts have been spent to investigate the effect of prestressing on the dynamic behaviour of prestressed concrete (PSC) beams. Whereas no agreement has been reached among the achievements obtained by different Researchers and among the theoretical and the experimental results for simply supported beams, very few researches have addressed this problem in continuous PSC beams. This topic is, indeed, worthy of consideration bearing in mind that many relevant bridges and viaducts in the road and railway networks have been designed and constructed with this structural scheme. In this paper the attention is, thus, focused on the dynamic features of continuous PSC bridges taking into account the effect of prestressing. This latter, in fact, contributes to the modification of the distribution of the bending stress along the beam, also by means of the secondary moments, and influences the flexural stiffness of the beam itself. The dynamic properties of a continuous, two spans bridge connected by a nonlinear spring have been extracted by solving an eigenvalue problem in different linearized configurations corresponding to different values of the prestress force. The stiffness of the nonlinear spring has been calculated considering the mechanical behaviour of the PSC beam in the uncracked and in the cracked stage. The application of the proposed methodology to several case studies indicates that the shift from the uncracked to the cracked stage due to an excessive prestress loss is clearly detectable looking at the variation of the dynamic properties of the beam. In service conditions, this shift happens for low values of the prestress losses (up to 20%) for structure with a high value of the ratio between the permanent load and the total load, as happens for instance in long span, continuous box bridges. In such conditions, the detection of the dynamic properties can provide meaningful information regarding the structural state of the PSC beam.

• Wind and Structures
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• v.20 no.2
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• pp.213-236
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• 2015

For high-speed railways (HSR) in wind prone regions, wind barriers are often installed on bridges to ensure the running safety of trains. This paper analyzes the effect of wind barriers on the running safety of a high-speed train to cross winds when it passes on a bridge. Two simply-supported (S-S) PC bridges in China, one with 32 m box beams and the other with 16 m trough beams, are selected to perform the dynamic analyses. The bridges are modeled by 3-D finite elements and each vehicle in a train by a multi-rigid-body system connected with suspension springs and dashpots. The wind excitations on the train vehicles and the bridges are numerically simulated, using the static tri-component coefficients obtained from a wind tunnel test, taking into account the effects of wind barriers, train speed and the spatial correlation with wind forces on the deck. The whole histories of a train passing over the two bridges under strong cross winds are simulated and compared, considering variations of wind velocities, train speeds and without or with wind barriers. The threshold curves of wind velocity for train running safety on the two bridges are compared, from which the windbreak effect of the wind barrier are evaluated, based on which a beam structure with better performance is recommended.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.640-649
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• 2010

Coarse granular materials such as gravel and crushed stone have been used as an important fill materials to large soil structure of railway, road, dam and so on. Although much studies for general soil materials have been carried out domestically, the studies for coarse materials were insufficient. Particularly, it is the level in which the study for dynamic properties(Elastic modulus and damping ratio) of coarse materials, applies the foreign country literature. This is due to the lack of large equipment for element test. But large soil structures made of coarse granular materials are generally important infrastructures. Therefore, the reliable design parameters for coarse materials should be obtained for safe and economic design, construction and maintenance. Triaxial test is the laboratory test method that is capable of controlling a confining pressure and boundary condition. In this project, we made a multi-purpose large triaxial testing system. This testing system is able to test coarse granular materials with maximum particle diameter of 100mm and support both the load control and displacement control. The load cell is installed inside of triaxial cell and the axial displacement is measured locally in order to control and measure more accurately in the small strain level. The verification test of this testing system was carried out with urethane verification specimens. So, from now on the useful information for coarse granular materials are expected to suggested by performing many tests with various material and condition.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.336-341
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• 2014

The articulated structures seen in train or tram applications are being applied in road transportation systems, for use in mass passenger transit. When articulated vehicles are driven on public roads, they no longer follow a guided track. Therefore, there are a lot of control elements that need to be considered, such as turning radius, swept path width, off-tracking, and swing-out. Some of the currently available articulated vehicles on roads are equipped with an independent drive system; a system that has one motor at each wheel. Through this drive system, each wheel can be independently controlled, making precise and quick dynamic stability control possible. In this paper, we propose a torque distribution algorithm that can reduce the overall turning radius of the articulated vehicle, which has been verified through dynamic simulation.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.06a
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• pp.103-116
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• 2003

Rockfall Protection fence is one of the most common rockfall Protection methods in Korea. If rockfall protection fences are required along the road or railway, their location, height and capacity, in terms of the maximum kinetic energy that they can absorb, should be specified. Within this paper, the best practice of rockfall barrier is introduced. Modern rockfall simulations as a means to define risks, protection requirements, dynamic loading and height of potential structures and selection of appropriate placement is presented. Technical possibilities of rockfall barriers and their actual limits are presented. Safety concepts based on probabilistic approaches are proposed. Recent studies peformed in other countries show that Flexible Barriers are also a feasible system to stop and retain debris flows. Finally an outlook onto further development is given.

• Smart Structures and Systems
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• v.14 no.3
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• pp.267-284
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• 2014

This paper aims to present the analytical solutions of 2-2 cement based piezoelectric transducers in series electrically based on the theory of piezo-elastic dynamics. The solutions of two different kinds of 2-2 cement based piezoelectric transducers under external harmonic load are obtained by using the displacement method. The effects of electrical connection of piezoelectric layers, loading frequency, thickness and distance of piezoelectric layers on the characteristics of the transducers are discussed. Comparisons with other related experimental investigations are also given, and good agreement is found. The proposed 2-2 cement based piezoelectric transducers have a great potential application in monitoring structural health in civil engineering and capturing mechanical energy or monitoring train-running safety in railway system and traffic safety in road system.