• The Journal of the Korea Contents Association
• /
• v.20 no.11
• /
• pp.669-675
• /
• 2020

This research has focused on comparing the capacity predicted by the theoretical formula with the one measured by field load tests to examine characteristics of the bearing capacity of a helical pile. The helical pile is featured by a central shaft with one or more helical-shaped bearing plates. Being established by a small rotary attached to an excavator that applies toque, the helical piles can be readily constructed at narrow sites, especially in an urban area with relatively less noise than the others requiring driving and excavation. Although many cases of the helical pile constructions can be recently found, the bearing capacity of the pile has been limitedly studied. To this end, this contribution analyzes and presents comprehensive results of the ten field loading tests with an application of different parameters depending on joint condition and specification of the helical piles, and types of tests and grouting.

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

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.5C
• /
• pp.343-350
• /
• 2006

The resistance bias factors for driven steel pipe piles are evaluated as a part of study to develop the LRFD(Load and Resistance Factor Design) for foundation structures in Korea. The 43 data sets of static load tests and soil property tests performed in the whole domestic area were collected and analyzed to determine the representative bearing capacities of the piles using various methods. Based on the statistical analysis of the data, the Davisson's criterion is proved to be the most reasonable method for estimation of pile bearing capacity among the methods used. The static bearing capacity formulas and the Meyerhof method using N values are applied to calculate the design bearing capacity of the piles. The resistance bias factors of the driven steel pipe piles are evaluated respectively as 0.98 and 1.46 by comparison of the bearing capacities for both of the static bearing capacity formulas and the Meyerhof method. It is also shown that uncertainty of the static bearing capacity formulas is relatively less than that of the Meyerhof method.

• Journal of the Korean Geotechnical Society
• /
• v.37 no.2
• /
• pp.19-31
• /
• 2021

Micropiles are cast-in-place piles with small diameters. The advantage of micropile is low construction expense and simple procedures, so it is widely applied to existing buildings and structures for the reinforcement of foundation and seismic performances. The base expansion structure has been developed following the original mechanism of horizontal expansion steps under compressive loading. This kind of structure can be installed at the pile end to improve the bearing capacity by tip area enlargement and horizontal force increment to the pile surface area. However, 'Micropile with base expansion structure' cannot be put into practical use, because detailed verification for the developed technique has not been conducted so far. In this research, 3-D numerical analysis was conducted to figure out the bearing mechanism of base expansion micropile and to verify the bearing capacity improvement compared to the general micropiles. 3-D modelling of micropile with base expansion structure was carried out and input parameter was determined. Bearing mechanism induced by base expansion structure was analyzed by lab-scale modelling, and bearing capacity improvement was verified by field-scale analysis.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2000.06a
• /
• pp.134-141
• /
• 2000

The real area of contacts, average film thickness, mean real pressure, and mean hydrodynamic pressure are investigated numerically in this study, especially for the parallel thrust bearing. Model surface is generated numerically with given autocorrelation function and some surface profile parameters. Then the average Reynolds equation contained flow factors and contact factor is applied to predict the effects of surface roughness in mixed lubrication regimes. In this equation, flow factors are defined as correction terms to smooth out high frequency surface roughness and contact factor is introduced to relieve from obtaining the average film thickness. Therefore the computation time to obtain h can be reduced.

• Transactions of Materials Processing
• /
• v.8 no.4
• /
• pp.331-339
• /
• 1999

In this study, to analyze the shaped drawing process from round bar, the practical conical die with considering die radius and bearing was defined by a mathematical expression, and also a simple technique for initial mesh generation to the shaped drawing process was proposed. The drawing of rectangular section from round bar, one of the shaped drawing process, has been simulated by using non-steady state 3D rigid plastic finite element method in order to evaluate the influence of semi-die angle and reduction in area to corner filling. Other process variables such as friction constant, rectangular ratio, die radius and bearing length were fixed during the simulation. An artificial neural network has been introduced to obtain the optimal process conditions which gave rise to a fast simulation.

• Tribology and Lubricants
• /
• v.16 no.6
• /
• pp.455-460
• /
• 2000

The real area of contacts, average film thickness, mean real pressure, and mean hydrodynamic pressure are investigated numerically in this study, especially for the parallel thrust bearing. Model surface is generated numerically with given autocorrelation function and some surface profile parameters. Then the average Reynolds equation contained flow factors and contact factor is applied to predict the effects of surface roughness in mixed lubrication regimes. In this equation, flow factors are defined as correction terms to smooth out high frequency surface roughness and contact factor is introduced to relieve from obtaining the average film thickness. Therefore the computation time to obtain barh h can be reduced.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2004.05a
• /
• pp.112-115
• /
• 2004

Bond between reinforcing bar and surrounding concrete is supposed to transfer load safely in the process of design of reinforced concrete structures. Bond failure of reinforcing bar generally take place by splitting of the concrete cover as bond force between concrete and reinforcing bars exceeds the confinement of the concrete cover and reinforcement. However, the confinement force has a limitation. Thus, the only variable is the bearing angle corresponding to the change of bond force. Higher rib height bars possessing higher shearing resistance can maintain higher bearing angle and higher splitting resistance when bars are highly confined, and consequently higher bond strength, than lower rib higher bars. In this study, from the evaluate bond strength of high Relative Rib Area Bars Using beam-end test specimens are compared with the current provisions for development of reinforcement, and the improved design method of bond strength is proposed.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.43-47
• /
• 1995

The ball screw is one of the important mechanical parts for the linear motion feeding systems. The usage of the ball screw has been growing in various industrial fields such as CNC machine tool, industrial robot and automated systems. Because of ever increasing demand for ball screws, increased accuracy and quality of the ball screw is needed,especially the surface roughness of the ball contact area in order to diminish noise and vibration. Therefore to improve the surface roughness of the area,we introduced magnetic assisted polishing which is one of the new potential polishing methods. In this study, diamond slurry and iron powder was used for magnetic assisted polishing of the ball bearing surface. This polishing process was experimentally confirmed to improve the surface roughness of the ball bearing.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.8
• /
• pp.27-37
• /
• 2010

Downdrag force develops when a pile is driven through a soil layer which will settle more than a pile. There is no obvious criterion for application of the current pile design method considering the negative skin friction. Therefore, in this study, numerical analyses were performed to investigate the behavior of a single pile subjected to negative skin friction and their results were used to determine the applicability of the current design method. Including three different sites in Song-do area and two different cases with friction pile and end bearing pile conditions, total six cases were considered. The load-settlement relationships and the neutral points were estimated for different end bearing conditions and the allowable bearing capacity of piles with negative skin friction was investigated through parametric studies. Based on the results showed that the negative skin friction made a major influence on the settlement of a pile and its stress. However the allowable bearing capacity may not be influenced by the negative skin friction. Compared with the allowable bearing capacity obtained from the ultimate bearing capacity with the safety factor of 3, the current design method with the safety factor of 3 underestimated the allowable bearing capacities regardless of the end bearing conditions. On the other hand, the current design method with the safety factor of 2 yielded reasonable results depending on the end bearing conditions.