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A Study on the Characteristics for the Ground Vibration Due to the Travelling Tilting Train

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Engineering（科研） 2013年第9期5卷 729-734页

作者： hee seok kim Structural Engineering Research Division Korea Institute of Construction Technology Republic of Korea

The development of the tilting train can contribute to solve the economic burden and enhance the transportation means of areas that did not share the benefits of the high speed railway. But the dynamic behavior caused by the interaction between the train and the track as well as the environmental vibrations along the railway should be evaluated to secure the safety of the train and riding comfort. In this paper a study on the characteristics for ground vibration due to the tilting train travelling in the conventional line are carried out. The transmitted load into the ground is computed through a study on the interrelation between the tilting car and the line. This load is applied into the numerical model which is one for the analysis of ground vibration due to the travelling tilting car. The far fields on the numerical model are formed by the absorbing boundary using dashpot, one of the most widely used absorbing boundary in finite element analysis. Using this numerical model, the analysis of the ground vibration characteristics caused by travelling tilting car is performed. From the analysis, it is shown that the transferred load due to the tilting train is larger than that of the conventional train.

关键词： Ground Vibration Tilting Car Absorbing Boundary

A Study on the Performance of Absorbing Boundaries Using Dashpot

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Engineering（科研） 2014年第10期6卷 593-600页

作者： hee seok kim Structural Engineering Research Division Korea Institute of Civil Engineering and Building Technology Goyang-si South Korea

In this paper an analytical study is carried out to examine the effectiveness of absorbing boundaries using dashpot. Validity of the absorbing boundary conditions suggested by Lysmer-Kuhle- meyer and White et al. is investigated by adopting the solution of Miller and Pursey. The Miller and Pursey’s problem is then numerically simulated using the finite element method. The absorption ratios are calculated by comparing the displacements at the absorbing boundary to those at the free field without the absorbing boundary. The numerical verification is carried out through comparison of displacement at the boundary.

关键词： Absorbing Boundary Dashpot Absorption Ratio

A Study on the Characteristics and the Effective Reduction Methods for the Ground Vibration Due to the Travelling Tilting Train

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Engineering（科研） 2014年第4期6卷 202-209页

作者： hee seok kim Structural Engineering Research Division Korea Institute of Construction Technology Goyang-Si Republic of Korea

In this paper, a study on the characteristics and the reduction methods of ground vibration due to the tilting train travelling in the conventional line is carried out. The load transmitted into the ground is computed considering the interaction between the tilting car and the line. This load is then applied in the numerical model for the analysis of ground vibration due to the travelling tilting car. The far-fields of the numerical model are modeled using the dashpot, as one of the most widely used absorbing boundaries in finite element analysis. Using this numerical model, the analysis of the ground vibration characteristics caused by the travelling tilting car and the analysis of the blocking effect of the ground vibration by wave barriers are performed. From the numerical analysis, it is shown that the blocking effect of the trench and the barrier filled with soft material is more effective than that of the barrier filled with hard material.

关键词： Component Ground Vibration Tilting Car Absorbing Boundary Wave Barrier

Finite Element Analysis with Paraxial &Viscous Boundary Conditions for Elastic Wave Propagation

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Engineering（科研） 2012年第12期4卷 843-849页

作者： hee seok kim Structural Engineering Research Division Korea Institute of Construction Technology Ilsan Republic of Korea

In this study, two studies are performed. One is to apply paraxial boundary conditions which are local boundary conditions based on paraxial approximations of the one-way wave equations to finite element analysis. To do this, a penalty functional is proposed and the existence and uniqueness of the extremum of the proposed functional is demonstrated. The other is to improve the capacity of viscous boundary conditions using dashpots. To do this, customary viscous boundary conditions are modified to maximize the efficiency according to angles of incidence and materials. For the numerical analysis of elasticity with paraxial boundary conditions and the modified viscous boundary conditions, the coding of the finite element models is implemented, and the efficiency of those boundary conditions is investigated.

关键词： Paraxial Boundary Local Boundary Penalty Functional Viscous Boundary

A Study on the Wave Screening Effectiveness According to Trench Dimensions Using Ultrasonic Waves

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Engineering（科研） 2014年第10期6卷 601-609页

作者： hee seok kim Won Jong Chin Structural Engineering Research Division Korea Institute of Construction Technology Goyang-si Republic of Korea

In this study numerical and experimental studies are conducted to examine the wave screening effectiveness of trenches. The numerical study relies on the finite element model of a sandbox with Lysmer-Kuhlemeyer absorbing boundaries. This model is used to examine the screening ef-fectiveness of trench studied for different trench dimensions and distances from the source and receiver to the trench. The results of the numerical analysis are compared with the results of the ultrasonic experiment performed on an acrylic block drilled with a rectangular cut. The comparison shows that the screening effectiveness of the trench is nearly equal if the depth of trench is larger than 60% of the surface wave length. It is also shown that if the distance between the trench and the source is longer than twice the surface wave length, the thickness of the trench does not affect the screening effectiveness.

关键词： Wave Screening Trench Absorbing Boundary Ultrasonic Wave

Postmortem ^(7)Li NMR analysis for assessing the reversibility of lithium metal electrodes in lithium metal batteries

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Journal of Energy Chemistry 2024年第7期94卷 430-440页

作者： Jaewon Baek Sunha kim hee-Tak kim Oc hee Han Department of Chemical&Biomolecular Engineering KAISTDaejeon 34141Republic of Korea Metropolitan Seoul Center Korea Basic Science InstituteSeoul 03759Republic of Korea Graduate School of Analytical Science&Technology Chungnam National UniversityDaejeon 34134Republic of Korea

Despite the proficiency of lithium(Li)-7 NMR spectroscopy in delineating the physical and chemical states of Li metal electrodes,challenges in specimen preparation and interpretation impede its *** this study,we conducted a comprehensive postmortem analysis utilizing ^(7)Li NMR,employing a stan-dard magic angle spinning probe to examine protective-layer coated Li metal electrodes and LiAg alloy electrodes against bare Li metal electrodes within Li metal batteries(LMBs).Our investigation explores the effects of sample burrs,alignment with the magnetic field,the existence of liquid electrolytes,and precycling on the ^(7)Li NMR *** contrasting NMR spectra before and after cycling,we identi-fied alterations in Li^(0) and Li^(+) signals attributable to the degradation of the Li metal *** NMR analyses decisively demonstrate the efficacy of the protective layer in mitigating dendrite and solid elec-trolyte interphase ***,we noted that Li*ions near the Li metal surface exhibit magnetic susceptibility anisotropy,revealing a novel approach to studying diamagnetic species on Li metal elec-trodes in *** study provides valuable insights and practical guidelines for characterizing distinct lithium states within LMBs.

关键词： NMR spectroscopy Lithium-7 Lithium metal battery Electrolyte Electrode-protective layer Solid electrolyte interface Magnetic susceptibility anisotropy Lithium-metal NMR signal Diamagnetic^(7)Li NMR signal

Experimental Study on Innovative Slip Form Method for the Construction of Tapered Concrete Pylon of Long-Span Cable Bridge

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Engineering（科研） 2014年第10期6卷 633-643页

作者： hee seok kim Young Jin kim Won Jong Chin Hyejin Yoon Structural Engineering Research Division Korea Institute of Civil Engineering and Building Technology Goyang-si South Korea

The construction of the three-dimensionally shaped pylons higher than 400 m requires a very high technological degree. It is known that the application of the tapered slip form method for the erection of the concrete pylon of long-span cable bridges offers the advantage of being significantly faster than applying the auto-climbing system (ACS) form method. Therefore, this study presents the development of an innovative slip form system for pylons with tapered cross-section. Surface wave inspection system is applied for the determination of slip-up time, wireless hydraulic control system is applied for auto rising, GPS system is used to manage the pylon configuration, and lightweight GFRP (Grass Fiber Reinforced Plastic) panels are applied in the slip form system. Small-scale tests were conducted three times to validate the performance of the developed core technologies, and full-scale tests were conducted twice to validate and verify the developed innovative slip form. The full-scale tapered concrete pylons have hollow shafts and a height of 10 m. The sectional dimensions are varied according to the construction height. The experimental constructions of the tapered pylons using the innovative slip form were conducted successfully. This system is the world’s first application of GFRP slip form panel.

关键词： Slip Form System Surface Wave Inspection System Wireless Hydraulic Control System Pylon Configuration Lightweight GFRP Panel

Development of Highly Efficient Construction Technologies for Super Long Span Bridge

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Engineering（科研） 2013年第8期5卷 629-636页

作者： hee seok kim Young Jin kim Won Jong Chin Hyejin Yoon Structural Engineering Research Division Korea Institute of Construction Technology Goyang-Si South Korea

This paper presents highly efficient cable erection equipments and methods related to the construction of super-long-span bridges, construction technology of high towers and, technology for offshore foundations currently developed through a R&D on accelerated and cost-saving construction technology for long-span cable bridges to secure our international competitiveness. In the field of cable erection technology, AS and PPWS equipments for highly efficient erection of cable longer than 2000 m, world-class clamping bolt tensioning equipment and shape control system for super-long cable are under development. The technologies developed in the domain of construction of towers are tapered slip form system for the construction of 400 m high tower, shape and erection precision control of elevated tower and, lightweight and modular formwork for slip form system. In the domain of foundation construction, remote controlled survey equipment and analysis system for water-depth of 100 m and depth of 50 m, prediction and evaluation technology of optimal load carrying capacity and settlement complying with international standard and, highly efficient hybrid foundation construction technology suitable for ground acceleration of 0.5 g and deep soft soil are currently developed.

关键词： AS Equipment PPWS Equipment Slip Form System Large Scale Foundation

Development of an Efficient Tapered Slip-Form System Applying BIM Technology

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Engineering（科研） 2013年第9期5卷 693-699页

作者： Hyejin Yoon Won Jong Chin hee seok kim Young Jin kim Global Technology Cooperation Center Korea Institute of Construction Technology Goyang South Korea Structural Engineering Research Division Korea Institute of Construction Technology Goyang South Korea

Slip-form system constitutes the latest technology for the erection of elevated concrete pylons. This paper investigates the design of slip-form system applying BIM technology for the efficient development of the slip-form system. The considered pylon has a height of 10 m and presents the rectangular hollow section generally adopted in cable-supported bridges. The slip-form was thus designed to accommodate the tapered cross-section and changing thickness considering the continuous placing of concrete. In addition, the safety of the system was examined with regard to the various loads applied on the slip form along the construction. The design results could be verified visually through BIM and the applicability of the designed slip-form was validated in advance through virtual assembly and construction.

关键词： Slip Form System Construction of Concrete Pylons BIM