• Proceedings of the KSME Conference
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• 2004.11a
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• pp.934-939
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• 2004

This paper propose a study on the Feed Characteristics of Twist Friction Driver. We are using Twist Friction Driving mechanism system. The system consists of Twist Friction Driver elements such as driving shaft, driven roller, Spring for pre-load, Air bearing guide, Servo motor, and measuring devices such as Encoder of Servo motor, Laser interferometer, LVDT . The Twist Friction driver is mechanically simple and very quiet at high speed, and has low pre-load. So The Twist Friction driver can materialize an ultra precision feed-resolution. The feed characteristics of the driver is determined by slip and angular error, backlash.

• Journal of the Korean Geotechnical Society
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• v.39 no.11
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• pp.71-84
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• 2023

In accordance with Korean structural foundation design standards, dynamic or static load tests are mandated for 1 to 3% of total piles. The construction quality of the remaining 97% to 99% of piles is determined through penetration measurements. This study aims to enhance the quality control of the majority of piles by adopting a pile driving formula that considers both penetration and hammer energy. The current challenge lies in adapting existing overseas driving formulas to the domestic site conditions, characterized by shallow weathered or soft rocks, and the prevalent use of pre-bored piles. To address this, the Modified Gates formula was refined using domestic dynamic load data, thereby improving its applicability to pile management. Despite employing fewer variables, the proposed formula demonstrates a comparable accuracy to dynamic loading tests in predicting the bearing capacity of pre-bored piles. Consequently, this formula holds promise for practical use in future pile quality management.

• Advances in concrete construction
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• v.1 no.2
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• pp.163-185
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• 2013

The use of post-compressed plates (PCP) to strengthen preloaded reinforced concrete (RC) columns is an innovative approach for alleviating the effects of stress-lagging between the original column and the additional steel plates. Experimental and theoretical studies on PCP-strengthened RC columns have been presented in our companion papers. The results have demonstrated the effectiveness of this technique for improving the strength, deformability and ductility of preloaded RC columns when subjected to axial or eccentric compression loading. An original and comprehensive design procedure is presented in this paper to aid engineers in designing this new type of PCP-strengthened RC column and to ensure proper strengthening details for desirable performance. The proposed design procedure consists of five parts: (1) the estimation of the ultimate load capacity of the strengthened column, (2) the design of the initial pre-camber displacement of the steel plate, (3) the design of the vertical spacing of the bolts, (4) the design of the bearing ends of the steel plates, and (5) the calculation of the tightening force of the bolts. A worked example of the design of a PCP-strengthened RC column is shown to demonstrate the application of the proposed design procedure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.6
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• pp.825-836
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• 2022

Micropiles can be used to support additional load in extended building structures. However, their use brings about a risk of exceeding the bearing capacity of existing piles. In this study, pre-compression was applied to distribute the load of an existing building to micropiles, and an indoor loading test was performed to confirm the structural applicability of a wedge-type anchorage device designed to improve its capacity. According to the test results, the maximum strain of the anchorage device was 0.63 times that of the yield strain, and the amount of slip generated at the time of anchorage was 0.11 mm, satisfying structural standards. In addition, using MIDAS GTS, a geotechnical finite element analysis software, the effect of the size of the pre-compression, the thickness of the soil layer, and the ground conditions around the tip on the reaction force of the existing piles and micropiles were analyzed. From the numerical analysis, as the size of the pre-compression load increased, the reaction force of the existing pile decreased, resulting in a reduction rate of up to 36 %. In addition, as the soil layer increased by 5 m, the reduction rate decreased by 4 %, and when the ground condition at the tip of the micropile was weathered rock, the reduction rate increased by 14 % compared with that of weathered soil.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.199-202
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• 2014

In recent years the downtown, Top-down method has been applied in a major method to solve the complaints due to noise, vibration, dust and safety issues such as cracking due to settlement when the excavation close to the building. Until it is installed underground permanent foundation, the Pre-founded Column is a pile foundation as well as a column to bear the upper construction load. The Pre-founded Column is constructed by PRD method generally. The EnP(Enlarging Pile) method can be expanded locally boring diameter of the embedment zone as compared to the PRD method existing general. Since the bearing capacity is increased by the boring diameter is expanded, the embedment length is reduced, the construction cost is reduced.

• Structural Engineering and Mechanics
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• v.65 no.4
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• pp.477-490
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• 2018

Reinforced concrete (RC) columns, as the primary load-bearing structural components in buildings, may need to be strengthened due to material deteriorations, changes in usage, new building codes or new design requirements. The use of post compressed plates (PCP) to strengthen existing RC columns has been proven experimentally and practically to be effective in solving stress-lagging effects between the original column and the new strengthening jacket caused by the pre-existing loads. This paper presents a comprehensive summary and review of PCP strengthening techniques to strengthen preloaded RC columns. The failure mode, deformability, and ductility of the strengthened RC columns are reviewed.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.360-366
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• 2001

This paper show the designing, manufacturing and performance test procedure of a high speed, fixed ratio planetary roller type traction drive as a speed reducer. The arrangement and size design for sun roller, planetary rollers and ring roller are carried out and a proper pre-load mechanism are adopted. To improve transmitting power capacity and endurance limit, nitro-carburized bearing steel and a synthetic traction oil are used. The manufactured and assembled traction drive operated successfully under unloaded conditions. Further tests for various load and speed conditions are executing now to improve the performance of the traction drive.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.582-588
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• 2007

Since the turnout system in railroad restricts the train speed, the KNR (Korean National Railroad) provides the specification for the speed (130km/h) of the train when the train passes the turnout system. Therefore, the turnout system in pre-existing railroad is necessary to be improved to speed-up for the train. In this study, the dynamic wheel-load field tests have been performed to evaluate the track performance and the roadbed bearing capacity has been examined using numerical analysis at the turnout crossing in the conventional and improved turnout system. The impact factor is estimated using the data sets achieved from the dynamic wheel-load field tests in the conventional and improved turnout system. The stress acting on the roadbed for the improved turnout system is substantially decreased compare to that for the conventional turnout system.

• Nuclear Engineering and Technology
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• v.54 no.1
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• pp.357-373
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• 2022

The high-temperature gas-cooled reactor pebble-bed module project is the first commercial Generation-IV NPP(Nuclear Power Plant) in China. A new joint is used for the vertical support of RPV(Reactor Pressure Vessel). The steel corbel is integrally embedded into the reactor-cabin wall through eight asymmetrically arranged pre-stressed high-strength bolts, achieving the different path transmission of shear force and moment. The vertical monotonic loading test of two specimens is conducted. The results show that the failure mode of the joint is bolt fracture. There is no prominent yield stage in the whole loading process. The stress of bolts is linearly distributed along the height of corbel at initial loading. As the load increases, the height of neutral axis of bolts gradually decreases. The upper and lower edges of the wall opening contact the corbel plate to restrict the rotation of the corbel. During the loading, the pre-stress of some bolts decreases. The increase of the pre-stress strength ratio of bolts has no noticeable effect on the structure stiffness, but it reduces the ultimate bearing capacity of the joint. A simplified calculation model for the elastic stage of the joint is established, and the estimation results are in good agreement with the experimental results.

• Smart Structures and Systems
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• v.16 no.3
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• pp.555-577
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• 2015

In the work at hand, the development of a morphing flap, actuated through shape memory alloy load bearing elements, is described. Moving from aerodynamic specifications, prescribing the morphed shape enhancing the aerodynamic efficiency of the flap, a suitable actuation architecture was identified, able to affect the curvature. Each rib of the flap was split into three elastic elements, namely "cells", connected each others in serial way and providing the bending stiffness to the structure. The edges of each cell are linked to SMA elements, whose contraction induces rotation onto the cell itself with an increase of the local curvature of the flap airfoil. The cells are made of two metallic plates crossing each others to form a characteristic "X" configuration; a good flexibility and an acceptable stress concentration level was obtained non connecting the plates onto the crossing zone. After identifying the main design parameters of the structure (i.e. plates relative angle, thickness and depth, SMA length, cross section and connections to the cell) an optimization was performed, with the scope of enhancing the achievable rotation of the cell, its ability in absorbing the external aerodynamic loads and, at the same time, containing the stress level and the weight. The conceptual scheme of the architecture was then reinterpreted in view of a practical realization of the prototype. Implementation issues (SMA - cells connection and cells relative rotation to compensate the impressed inflection assuring the SMA pre-load) were considered. Through a detailed FE model the prototype morphing performance were investigated in presence of the most severe load conditions.