• 한국항만학회지
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• 제14권4호
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• pp.441-450
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• 2000

In order to improve the water quality in semi-enclosed bays, Gug et al. (1997) have proposed a new method to activate the tidal exchange by creation and control of tidal residual current through the addition of artificial elements to creation and control of tidal residual current through the addition of artificial elements to create bottom roughness, so, ot is advisable to arrange as few of these as possible from a point of cost-benefit view. This paper attempts to develop the most suitable shape of artificial bottom roughness units with which to create and control an optimal tidal residual current. Several simple shapes were examined as fundamental cases. Subsequently 38 types of artificial bottom roughness units based on a few simple effective shapes, were examined experimentally. As a result of this research, two types to create artificial roughness.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 춘계 학술기술논문발표대회 논문집
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• pp.37-40
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• 2005

High Performance Concrete(HPC) has been widely used in high-rise building. The HPC has several benefits including high strength, high fluidity and high durability. However. spatting is susceptible to occur in HPC and HPC also tends to be deteriorated in the side of fire resistance performance at fire. This paper focuses on the analysis of the temperature history and residual compressive strength with finishing material, in order to protect HPC from sudden-high-temperature, which is one of the main reason spatting occurs. Test results show that spalling occurs in all specimens. The most serious spalling took placed in HPC covering fire enduring spray-on material, whose covering thickness is 20mm but temperature history indicates that fire enduring spray effectively protected HPC from fire for more than 2hours. In addition, residual compressive strength ratio of HPC using fire enduring paint was more than $90\%$ of original strength, thus minimizing spatting and indicating significant fire resistance performance.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.553-556
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• 2004

This paper is to investigate the spalling and fire endurance of high performance RC column member with PP fiber and lateral confinement of metal lath and non fire resistance removal type form. According to test results, combination of PP fiber and metal lath as well as use fire resistance non removal type form had favorable fire resistance by discharging internal vapour pressure and lateral confining. After fire endurance test, compressive strength decreased markedly caused by internal expansion pressure and crack. Residual strength of plain concrete was decreased to $22\%$. The use of PP fiber and lateral confinement of metal lath and non removal type form enhanced the residual strength above $40\%$. Especially, the combination of $0.1\%$ of PP fiber and lateral confinement with the level of 2.3T exhibited more than $51\%$ of residual strength. Therefore, to improve fire endurance and spalling resistance, the combination of $0.1\%$ of PP fiber and metal lath with 2.3T can be the proper measure.

• 대한조선학회논문집
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• 제59권4호
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• pp.243-250
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• 2022

In the design stage of hull forms, a fast prediction method of resistance performance is needed. In these days, large test matrix of candidate hull forms is tested using Computational Fluid Dynamics (CFD) in order to choose the best hull form before the model test. This process requires large computing times and resources. If there is a fast and reliable prediction method for hull form performance, it can be used as the first filter before applying CFD. In this paper, we suggest the offset-based performance prediction method. The hull form geometry information is applied in the form of 2D offset (non-dimensionalized by breadth and draft), and it is studied using Convolutional Neural Network (CNN) and adapted to the model test results (Residual Resistance Coefficient; C_R). Some additional variables which are not included in the offset data such as main dimensions are merged with the offset data in the process. The present model shows better performance comparing with the simple regression models.

• 한국지반환경공학회 논문집
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• 제6권1호
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• pp.45-51
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• 2005

말뚝을 설계함에 있어 극한지지력을 산정하는 것만으로는 말뚝의 장기 거동에 있어서의 하중분포를 고려할 수 없으므로 재하시험시 변형률계나 응력계를 사용하여 말뚝의 하중 재하에 따른 주면저항(the shaft resistance)의 분포를 측정하고 있다. 그러나 대부분의 재하시험시 하중이 '0'일 때를 'zero time'으로 하여 계측기의 값을 읽는 'zero reading'을 가정함으로써 현장타설말뚝이나 항타말뚝의 시공시 발생된 잔류응력(the residual stress 또는 the residual load)을 무시하고 있다. 이러한 'zero reading'의 가정은 말뚝 시공시 발생하는 말뚝 하방향으로의 부주면마찰력인 잔류응력을 고려하지 않으므로 실제 말뚝주면의 하중분포와는 다른 결과를 보이게 된다. 본 연구에서는 현장에 시험시공된 현장타설말뚝에 대하여 정재하시험을 수행하였고, 말뚝 주면의 하중분포 측정시 변형률계를 사용하여 콘크리트 타설 직후부터 계측을 실시함으로써 말뚝 시공에 따른 잔류응력을 측정하였다. 그 결과, 잔류응력이 고려된 경우는 초기에 부의 응력상태를 보이나 하중이 재하됨에 따라 부주면마찰력이 극복되면서 양의 주면마찰력으로 전환됨을 알 수 있었으나, 'zero reading'의 경우는 양의 주면마찰력 만을 보였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.419-433
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• 2009

Pressure grouting is a common technique in geotechnical engineering to increase the stiffness and strength of the ground mass and to fill boreholes or void space in a tunnel lining and so on. Recently, the pressure grouting has been applied to a soil-nailing system which is widely used to improve slope stability. The soil-nailing design has been empirically performed in most geotechnical applications because the interaction between pressurized grouting paste and the adjacent ground mass is complicated and difficult to analyze. The purpose of this study is to analyze the increase of pullout resistance induced by pressurized grouting with the aid of performing laboratory model tests and field tests. In this paper, two main causes of pullout resistance increases induced by pressurized grouting were verified: the increase of residual stress; and the increase of coefficient of pullout friction. From the laboratory tests, it was found that residual stress in borehole increases by pressurized grouting and dilatancy angle could be estimated by cavity expansion theory using the measured wall displacements. From the field test results, the pullout resistance of soil-nailing with pressurized grouting was found to be 10% larger than that of soil-nailing with gravitational grouting, mainly caused by mean normal stress increase and dilatancy effect. So, the pullout resistance could be estimated by considering these two effects. The radial displacement increases with dilatancy angle increase and the dilatancy angle decreases with injection pressure increase. The measured pullout resistance obtained from field tests is in good agreement with the estimated one from the cavity expansion theory.

• 대한조선학회지
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• 제9권1호
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• pp.15-20
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• 1972

As the technique of resistance spot welding became more and more advanced the factors hitherto considered secondary become more and more important. Among these factors the distribution of heat and temperature during resistance spot welding is particularly important in conjunction with thermal stress, strain and residual stress, strain problems. The analytical investigations upon the transient temperature due to resistance spot welding were made for the carbon steel plate and aluminum alloy plate. The numerical values obtained by the analytical investigation are nearly identical with the temperature distribution which obtained by D.J. Sullivan and some other experimental data. It was thought therefore useful to estimate the heat effect upon the material such as a residual stress and strain, metalurgical change, change in physical properties and etc.

• 대한기계학회논문집A
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• 제24권2호
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• pp.378-385
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• 2000

Fracture resistance (J-R) curves, which are used for elastic-plastic fracture mechanics analyses, decreased under tension-compression loading condition. This phenomenon was proved by several former researches, but the causes have not been clear yet. The objective of this paper is to investigate the cause of this phenomenon. On the basis of fracture resistance curve test results, strain hardening hypothesis, stress redistribution hypothesis and crack opening hypothesis were built. In this study, hardness tests, Automated Ball Indentation(ABI) tests, theoretical stress field analyses, and crack opening analyses were performed to prove the hypotheses. From this study, strain-hardening of material, generation of tensile residual stress at crack tip, and crack opening effects are proved as the causes of the decrease hypothesis.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권2호
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• pp.55-61
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• 2002

In this paper, 'lifetime-temperature rise model' based on the 'lifetime-resistance model' is theoretically Proposed, in order to find out the evaluation method of degradation and the residual lifetime by use of infrared image camera for electric connections/contacts. Two assumptions have been builded up for the 'lifetime-temperature rise model': one is associated with the linear relationship between the temperature ism ΔK and contact resistance, and the other the functional relationship between the temperature of electric connections/contacts and the operating time presenting in the 'lifetime-resistance model'. To prove the proposed model, experiments have been performed for various electric connections/contacts. From the experimental results, measured values were quite similar to the calculated values, which proved the above-mentioned two assumptions. Therefore, by use of 'lifetime-temperature rise model', it is possible to estimate the trend of degradation and the residual lifetime for electric connections/contacts through the temperature measurements .

• 한국해양공학회지
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• 제10권2호
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• pp.88-97
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• 1996

The pupose of this study is to improve the mechanical properies and to evaluate the residual stresses of flame-sprayed Alumina ceramic coating layer. The first work in this study is to investigate the effects of strengthening heat treatments on the mechanical properties of coating layer. Strengthening heat treatments for sprayed specimens were carried out in vaccum furnace. The mechanical properties such as microhardness, thermal shock resistance, adhesive strength and erosion resistance were tested for the sprayed specimens after strengthening heat treatments. And it was clear that the mechanical properties of coating layer were much improved by strengthening heat treatments. The second work in this study is to evalute the residual stresses in coating lsyer by numerical analysis. FDM and FEM were used to analyze temperature distribution and residul stresses in coating layer. It was proved that are tensile stresses in coating layer and that residual stresses can be controlled by the appropriate selection of the spraying parameters such as preheat temperature, coating thickness and bond coat thickness.