• 한국주조공학회지
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• 제10권4호
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• pp.332-341
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• 1990

The structure and tensile properties of the unidirectionally solidified Al-33wt.%Cu alloy have been investigated. Casted Al-33wt.%Cu alloy was unidirectionally solidified with rates (R) between 1㎝/hr and 24cm/hr maintaining the thermal gradient(G) at solid-liquid interface, $32^{\circ}C/cm$ and $21^{\circ}C/cm$. The entectic struture was varied according to the growth condition(G/R radio). When G/R ratio was larger than $8.5{\times}10^3$ $^{\circ}C/cm^2/sec$ the lamellar structure was formed, and colony structure was formed when G/R ratio was smaller than $8.5{\times}10^3$ $^{\circ}C/cm^2/sec$. The interlamellar spacing(${\gamma}$) in the above alloy system was vaired with the growth rate(R) According to "${\gamma}^2{\cdot}R＝8.8{\times}10＾{-11}cm^2/sec$" relationship. The yield stress (${\sigma}$0.001) and UTS for samples in the as-grown condition increased with the interlamellar spacing decrease and the values corresponding to colony structure are lower than those corresponding to amellar structure with the same lamellar spacing. The yield stress for samples in aged condition did not change with the interlamellar spacing.

• 한국지반공학회논문집
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• 제27권4호
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• pp.77-87
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• 2011

이 연구에서는 실내에서 스미어가 발생한 지반을 모사하고 배수재 간격에 따른 스미어의 영향이 차후의 압밀거동에 미치는 영향을 분석하기 위하여 대형압밀챔버와 모형 맨드렐 관입 장비를 이용하여 다양한 압밀시험을 실시하였고 연직배수공법의 효율을 분석하였다. 실험결과 과압밀 영역에서는 스미어의 영향범위가 증가함에 따라 침하량도 증가하였으나, 정규압밀영역에서 스미어에 의한 침하량의 차이는 나타나지 않았다. 일반적으로 연직배수재를 설치한 경우 압밀속도를 향상시킬 수 있지만, 배수재 간격비가 감소하고 배수거리가 짧아지더라도 짧아진 배수거리만큼 압밀속도가 빨라지지는 않으며 오히려 압밀효율은 감소한다.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.609-615
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• 2016

Measuring similarity between two signals is a key element of the location template matching (LTM) method which is one of impact source localization technique. As a measure of similarity, the correlation coefficient is most widely used, and the group delay based method is recently proposed to improve the accuracy of finding the impact source. In practice, the LTM method assumes that the similarity between two signals decreases as the distance between two corresponding impact points increases, where the distance between two neighboring impact points defines the grid spacing. In this paper, it is shown that this assumption is not always true but the correlation coefficients fluctuate forming a main robe and many side robes as the distance between two neighboring impact points increases. On the other hand, the standard deviation of group delay sharply increases with a small increase of the grid spacing. These are demonstrated by using a simple cantilever beam. Based on these findings, an optimal way of implementing the LTM method may be suggested by combining the correlation coefficient and the group delay based approaches.

• Advances in concrete construction
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• 제10권2호
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• pp.151-159
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• 2020

An experimental study on the stress-strain relation of PVC-CFRP confined reinforced concrete columns subjected to eccentric compression was carried out. Two parameters, such as the CFRP strips spacing and eccentricity of axial load, were considered. The experimental results showed that all specimens failed by compressive yield of longitudinal steel bar and rupture of CFRP strips. The bearing capacity of specimen decreases as the eccentricity or the CFRP strips spacing increases. The stress-strain relation of specimens undergoes two stages: parabolic and linear stages. In the parabolic stage, the slope of stress-strain curve decreases gradually as the eccentricity of axial loading increases while the CFRP strips spacing has little effect on the slope of stress-strain curve. For the linear stage, the slope of stress-strain curve decreases as the eccentricity of axial load or the CFRP strips spacing increases. A model for predicting the stress-strain relation of columns under eccentric compression is proposed and it agrees well with various test data.

• 열처리공학회지
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• 제33권6호
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• pp.271-276
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• 2020

The relationship between the hardness and interlamellar spacing of discontinuous precipitates (DPs) formed by continuous cooling was studied for Mg-9%Al-1%Zn alloy. After solution treatment at 683 K for 24 h, the specimens were cooled to room temperature with different cooling rates ranging from 0.2 to 2 K·min^-1, in order to obtain DPs with various interlamellar spacings. It was found that cooling rate of 2 K·min^-1 yielded only small amount of nodular DPs at the grain boundaries, while cooling rates below 2 K·min^-1 yielded both DPs and continuous precipitates (CPs). The volume fraction of DPs increased with increasing cooling rate up to 0.5 K·min^-1, over which it abruptly decreased. The hardness of DPs was increased with an increase in the cooling rate, whereas the interlamellar spacing of the DPs was decreased with respect to cooling rate. The hardness of the DPs formed by continuous cooling was correlated with the interlamellar spacing and can follow a Hall-Petch type relation as in the case of pearlite with lamellar morphology.

• Structural Engineering and Mechanics
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• 제47권1호
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• pp.75-98
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• 2013

This study focuses on shear strengthening performance of simply supported reinforced concrete (RC) T-beams bonded by glass fibre reinforced polymer (GFRP) strips in different configuration, orientations and transverse steel reinforcement in different spacing. Eighteen RC T-beams of 2.5 m span are tested. Nine beams are used as control beam. The stirrups are provided in three different spacing such as without stirrups and with stirrups at a spacing of 200 mm and 300 mm. Another nine beams are used as strengthened beams. GFRP strips are bonded in shear zone in U-shape and side shape with two types of orientation of the strip at $45^{\circ}$ and $90^{\circ}$ to the longitudinal axis of the beam for each type of stirrup spacing. The experimental result indicates that the beam strengthened with GFRP strips at $45^{\circ}$ orientation to the longitudinal axis of the beam are much more effective than $90^{\circ}$ orientation. Also as transverse steel increases, the effectiveness of the GFRP strips decreases.

• Steel and Composite Structures
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• 제29권5호
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• pp.659-667
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• 2018

This paper deals with the experimental study on strength the strength and deformation characteristics of short circular Concrete Filled Steel Tube (CFST) columns. Effect of vertical stiffeners on the behavior of the column is studied under axial compressive loading. Intermittently welded vertical stiffeners are used to strengthen the tubes. Stiffeners are attached to the inner surface of tube by welding through pre drilled holes on the tube. The variable of the study is the spacing of the weld between stiffeners and circular tube. A total of 5 specimens with different weld spacing (60 mm, 75 mm, 100 mm, 150 mm and 350 mm) were prepared and tested. Short CFST columns of height 350 mm, outer tube diameter of 165 mm and thickness of 4.5 mm were used in the study. Concrete of cube compressive strength $41N/mm^2$ and steel tubes with yield strength $310N/mm^2$ are adopted. The test results indicate that the strength and deformation of the circular CFST column is found to be significantly influenced by the weld spacing. The ultimate axial load carrying capacity was found to increase by 11% when the spacing of weld is reduced from 350 mm to 60 mm. The vertical stiffeners are found to effective in enhancing the initial stiffness and ductility of CFST columns. The prediction models were developed for strength and deformation of CFST columns. The prediction is found to be in good agreement with the corresponding test data.

• Journal of the Korean Wood Science and Technology
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• 제30권3호
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• pp.97-103
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• 2002

This study was carried out to obtain basic information on racking resistance of shear walls and the factors affecting racking resistance of shear walls. Shear walls constructed by larch lumber nominal 50 mm × 100 mm framing and various sheathing materials were tested by applying monotonic and cyclic load functions. Shear walls with various stud spacing such as 305 mm, 406 mm, and 610 mm were tested under both of monotonic and cyclic loads and shear walls with various aspect (height-width) ratios were tested under cyclic load functions. The effect of hold-down connectors in shear walls was also tested under cyclic load functions. Racking resistance of shear walls has very close linear relation with stud spacing and width of shear walls. The ultimate racking strength of shear walls was reached at around or before the displacement of 20 mm. It was proposed in this study that the minimum racking strength and minimum width for shear wall be 500 kgf and 900 mm, respectively. Load-displacement curves obtained by racking tests under monotonic load functions can be represented by three straight line segments. Under cyclic load functions, envelope curves can be divided into three sections that can be represented by straight lines and the third section showed almost constant or decreasing slope.

• Geomechanics and Engineering
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• 제36권1호
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• pp.71-81
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• 2024

This study analyzes the pull-out behavior of tunnel-type anchorage under various joint conditions, including joint direction, spacing, and position, using a finite element analysis. The validity of the numerical model was evaluated by comparing the results with a small-scaled model test, and the results of the numerical analysis and the small-scaled model test agree very well. The parametric study evaluated the quantitative effects of each influencing factor, such as joint direction, spacing, and position, on the behavior of tunnel-type anchorage using pull-out resistance-displacement curves. The study found that joint direction had a significant effect on the behavior of tunnel-type anchorage, and the pull-out resistance decreased as the displacement level increased from 0.002L to 0.006L (L: anchorage length). It was confirmed that the reduction in pull-out resistance increased as the number of joints in contact with the anchorage body increased and the spacing between the joints decreased. The pull-out behavior of tunnel-type anchorage was thus shown to be significantly influenced by the position and spacing of the rock joints. In addition, it is found that the number of joints through which the anchorage passes, the wider the area where the plastic point occurs, which leads to a decrease in the resistance of the anchorage.

• 한국환경농학회지
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• 제34권3호
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• pp.204-209
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• 2015

본 연구는 시장점유율이 가장 높은 가을무 두 품종을 이용하여 적정 재식거리를 구명하고자 실시하였다. 열간거리 $55{\times}25$, $45{\times}25$, $35{\times}25$ 및 $25{\times}25cm$ 등 4 실험구로, 주간거리 $35{\times}28$, $35{\times}25$, $35{\times}22$ 및 $35{\times}19cm$ 등 4 실험구로 파종하여 파종 58일 후 수확하여 지상부 및 지하부 생육과 뿌리 품질을 조사하였다. 두 품종 모두 열간거리에 따른 지상부 생육의 차이는 없었다. 하지만 열간거리 25 cm에서 S품종의 근장 및 C품종의 근중이 각각 20.5 cm, 1,422 g으로 다른 처리에 비해 통계적으로 유의하게 적었다. 따라서 가을무의 두 줄 재배시 열간거리는 근중이 감소하지 않고 무의 품질에도 영향을 미치지 않는 35 cm가 적절한 것으로 판단된다. 주간거리는 두 품종 모두 28, 25 및 22 cm에서는 평균 1,500 g 이상의 적절한 크기의 무가 생산되었으나 C품종의 경우 19 cm 실험구에서 근중이 1148.3 g으로 다른 실험구에 비해 크게 감소하였다. S품종의 경우, 주간거리는 무의 수량 및 품질에 큰 영향을 미치지 않았으나 C품종의 경우 주간거리에 의해 지상부 및 지하부 생육이 크게 영향을 받는 것으로 나타났다. 당도와 바람들이는 재식거리에 따라 영향을 받았지만 그 차이는 적었다. 따라서 가을무 두 줄 재배시 적정 재식거리는 최소 열간거리 25 cm, 주간거리 19 cm 이상 설정하는 것이 가을무 재배에 유리할 것으로 판단된다.