• International Journal of Railway
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• v.8 no.2
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• pp.35-41
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• 2015

Tilting-train is very attractive to the railroad users in the world due to the advantage of high speed in curved track using pre-existing infrastructure of railway. Tilting-train has a unique allowable speed and mechanism especially in curved track. In this work, when tilting-train is operated with the allowable speed, the behavior of roadbed is evaluated by examining its settlement and bearing capacity. Additionally, the stability of roadbed is estimated as the roadbed is in the condition of soft soil influenced by the weather effects and cyclic train loading. Numerical results show that the roadbed settlement satisfies the allowable settlement when the elastic modulus of upper roadbed should be greater than $5000t/m^2$.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.53-54
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• 2002

New lubrication mechanism for nanomachine is proposed. This mechanism utilizes the effect of diffusive double layer observed in hydrophobic colloidal solution. Basic idea of the theory is inspired by the research for possible mechanism of bacterial flagellar motor In this study, formulation of this mechanism is achieved and numerical calculation is performed. It is shown that this mechanism can produce enough load capacitance. Furthermore not only capacitance to sustain driving force of flagellar motor

• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.51-60
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• 2003

As piling works in urban area are increasing, SIP which has low noise & vibration piling method takes the place of driven pile which has good bearing charateristics and is economical. Although SIP has been used far more than 15 years and it's use is increasing year by year, accurate analysis of bearing mechanism of SIP is not enough. So the design of SIP is much more conservative than driven pile. This paper is aimed at analysing the bearing charateristics of 103 SIPs constructed in Korea to give rational design criteria. Research result shows that bearing capacity of SIP is 40% lower than that of driven pile and conservative Meyerhof(20$\bar{N}_b'A_b$) method produced closer result to load test results than any other design method. And this result shows that in order to use optimised design criteria for the economical SIP design, quality control criteria must be settled down to produce high bearing capacity.

• Geomechanics and Engineering
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• v.14 no.4
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• pp.345-354
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• 2018

Currently, layered geogrid method (LGM) is the commonly practiced technique for reinforcement of slopes. In this paper the geogrid-box method (GBM) is introduced as a new approach for reinforcement of rock-soil slopes. To achieve the objectives of this study, a laboratory setup was designed and the slopes without reinforcements and reinforced with LGM and GBM were tested under the loading of a circular footing. The effect of vertical spacing between geogrid layers and box thickness on normalized bearing capacity and failure mechanism of slopes was investigated. A series of 3D finite element analysis were also performed using ABAQUS software to supplement the results of the model tests. The results indicated that the load-settlement behavior and the ultimate bearing capacity of footing can be significantly improved by the inclusion of reinforcing geogrid in the soil. It was found that for the slopes reinforced with GBM, the displacement contours are widely distributed in the rock-soil mass underneath the footing in greater width and depth than that in the reinforced slope with LGM, which in turn results in higher bearing capacity. It was also established that by reducing the thickness of geogrid-boxes, the distribution and depth of displacement contours increases and a longer failure surface is developed, which suggests the enhanced bearing capacity of the slope. Based on the studied designs, the ultimate bearing capacity of the GBM-reinforced slope was found to be 11.16% higher than that of the slope reinforced with LGM. The results also indicated that, reinforcement of rock-soil slopes using GBM causes an improvement in the ultimate bearing capacity as high as 24.8 times more than that of the unreinforced slope.

• Steel and Composite Structures
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• v.27 no.4
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• pp.495-508
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• 2018

In this paper, cyclic loading tests on composite frame inner joints of steel-reinforced recycled concrete (SRRC) column-steel beam were conducted. The main objective of the test was to obtain the shear behavior and analyze the shear strength of the joints. The main design parameters in the test were recycled coarse aggregate (RCA) replacement percentage and axial compression ratio. The failure process, failure modes, hysteresis curves and strain characteristics of the joints were obtained, and the influences of design parameters on the shear strength of the joints have been also analysed in detail. Results show that the failure modes of the joints area are typical shear failure. The shear bearing capacity of the joints maximally decreased by 10.07% with the increase in the RCA replacement percentage, whereas the shear bearing capacity of the joints maximally increased by 16.6% with the increase in the axial compression ratio. A specific strain analysis suggests that the shear bearing capacity of the joints was mainly provided by the three shear elements of the recycled aggregate concrete (RAC) diagonal compression strut, steel webs and stirrups of the joint area. According to the shear mechanism and test results, the calculation formulas of the shear bearing capacity of the three main shear elements were deduced separately. Thus, the calculation model of the shear bearing capacity of the composite joints considering the adverse effects of the RCA replacement percentage was established through a superposition method. The calculated values of shear strength based on the calculation model were in good agreement with the test values. It indicates that the calculation method in this study can reasonably predict the shear bearing capacity of the composite frame inner joints of SRRC column-steel beam.

• Tribology and Lubricants
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• v.35 no.2
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• pp.114-122
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• 2019

High-speed rotating machinery requires low cost and reliable bearing elements with low friction, stable rotordynamic characteristics, and a simple design. This study experimentally evaluates the effects of bearing-support elements on the vibrational characteristics of a small-sized, high-speed permanent magnetic motor. A series of coast down tests from 100 krpm characterize the vibrational behaviors, rotor displacement, and housing acceleration of motors supported by ball bearings, ball bearings with a metal mesh damper, and gas foil bearings, respectively. Two eddy-current sensors installed in the horizontal and vertical directions measure the displacement of the rotor at its front nut, and a 3-axis accelerometer attached to the motor housing measures the housing acceleration. The test results reveal that synchronous (1X) vibration components most significantly affect the rotor displacement and housing acceleration, independent of the bearing-support elements. The motor supported by the deep-groove ball bearings results in the largest rotor vibrations increasing with speed; this is due to the absence of a damping mechanism. Additionally, the metal mesh damper effectively reduces the rotor displacement, housing acceleration, and sound-pressure level in the high-speed region (i.e., above 40 krpm), thus implying its substantial damping performance when installed on the outer race of the ball bearing. Lastly, the gas foil bearing supported motor yields the smallest rotor displacement, housing acceleration, and lowest sound-pressure level because of its hydrodynamic airborne operation, which does not require rolling elements that may cause mechanical friction and vibrations.

• Journal of the Korean GEO-environmental Society
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• v.4 no.4
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• pp.85-96
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• 2003

The Geocell system is the advanced system of Geo-grids, and is one of geosynthetics used for earth reinforcement of weak soil. It is the way to increase earth strength and bearing capacity by using three dimension type of geo-composite. This paper analyzed the bearing capacity mechanism of Geocell system for earth reinforcement. Plate loading tests under the model laboratory condition were performed, and the increase of bearing capacity and the decrease of settlement with shallow foundation were evaluated.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.389-396
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• 1999

In this study compressive and tensile load tests have been performed to investigate reinforcing effect and load transfer mechanism of small diameter piles installed in the foundation soil for the marine suspension bridge. Load tests were carried out on steel plate with diameters of 50cm, 100cm and 150cm varying loads starting from 39 tons up to 314 tons. Small diameter piles were proved to behavior like as friction piles and loads were not transmitted to the bottom of piles. From pull-out tests, the uplift capacity of small diameter piles was largely influenced by reinforcing materials compared to frictional resistance between piles and adjacent soils. The bearing capacity of small diameter piles appeared to be higher than the ultimate bearing capacity evaluated using static formulae. The load carrying capacity of small diameter piles was superior to the bored piles with a similar size. Thus, ultimate bearing capacity estimated from static formulae can provide conservative designs and thereby resulting in economic disadvantages. A further study to accumulate data regarding various soil conditions is recommended for an improved estimation of bearing capacity of piles with small diameter.

• Steel and Composite Structures
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• v.14 no.4
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• pp.313-333
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• 2013

The web-encased steel-concrete composite (WESCC) beam is a new developed steel-concrete composite beam. Experiments of six simply supported WESCC beam specimens were conducted. The effects of the shear-span ratio and steel section type were all investigated on the static behaviors such as failure modes, failure mechanism and bearing capacity. The experimental results denoted that all specimens failed in bending mode and the degree of combination between the bottom armor plate of steel shape and concrete were very well without any evident slippage, which demonstrated that the function of bottom armor plate and web were fully exerted in the WESCC beams. It could be concluded the WESCC beams have high stiffness, high load carrying capacity and advanced ductility. The design methods are proposed which mainly consist the bearing capacity calculation of bending and flexural rigidity. The calculation results of the bearing capacity and deflection which take the shear deflection into account are in agreement with the experimental results. The design methods are useful for design and application of the innovative composite beams.

• Geotechnical Engineering
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• v.14 no.4
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• pp.117-128
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• 1998

Solid mattress foundation using geogrid has often been used on soft grounds to increase the bearing capacity, and its effect has received much recognition. Geogrid-mattress system is the method of construction which increases the bearing capacity and the effect of controlling settlement by dispersing load to wider foundation through its stiffness. But ifs mechanism has not been examined exactly yet. considered to be influential factors in the experiments. As a result of the experiments, the characteristic of dispersing stress under mattress foundations was understood and the way of calculating the bearing capacity in designing the mattress foundations was suggested.