• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.533-538
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• 2010

This study was performed for evaluate permeability in base of development material and existing grouting. And examined durability by age strength when devide seawater and fresh water that water curing. Executed permeability test to choose base to produce pouring in specimen. About 5 grouting material, produced pouring in specimen. Seawater strength of all grouting materials except BGI decreased gradually as result that divide seawater and fresh water that water curing.

• 한국주조공학회지
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• 제24권2호
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• pp.94-100
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• 2004

Gas porosity which is a common defect in aluminum alloy casting, is also thought to be severer in aluminum alloy castings produced by lost foam process due to the pyrolysis of the polystyrene foam pattern during pouring. Fundamental experiments were carried out to evaluate the effect of process variables such as the melt treatment, the cooling rate and pouring temperature on the density and mechanical properties in A356.2 castings with simple bar shape. The density of grain refined specimen was slightly lower than that of degassed one, but was higher than that of no treated one and that of shot ball packed specimen was higher than the other specimens. The tensile strength and elongation were in the ranges of $200{\sim}230MPa$ and $0.5{\sim}1.5%$ respectively. The density and hardness of lost foam cast specimens decreased with increase in pouring temperature.

• Steel and Composite Structures
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• 제51권1호
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• pp.9-24
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• 2024

In order to study the shear mechanical behavior of prefabricated and assembled multi-key group stud connectors, this paper conducted push-out tests on 10 prefabricated and assembled multi-key group stud connectors, distributed in 5 groups, and detailed the failure modes of each specimen. Based on the finite element software, a total of 22 models of this type of stud connector are established, and validated the finite element models using the push-out tests. Furthermore, the effects of stud diameter, number of key groups, and spacing of key groups on the shear resistance of prefabricated and assembled multi-key group stud connectors are analyzed. Combined with the test and finite element, the force analysis is carried out for the stud and first-pouring and post-pouring concrete. The results show that the spacing and number of key groups have a significant impact on the shear capacity and shear stiffness of the specimen. For a single stud, the shear force is transferred to the surrounding concrete via the stud's root. When the stud is finally cut, the steel and the concrete plate are separated. Under vertical shear force, the top row of studs experiences the highest shear, while the middle row has the least. Based on statistical regression, a formula of assembled multi-key group stud connectors is proposed.

• 한국공간구조학회논문집
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• 제23권1호
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• pp.61-68
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• 2023

Buckling Restrained Braces can not only express the strength considered at the time of design, but also reduce the seismic load by energy dissipation according to the plastic behavior after yield deformation of the steel core. The physical characteristics and damping effect may be different according to the buckling prevention method of the steel core by the lateral restraint element. Accordingly, in this study, To compare hysteresis characteristics, Specimen(BRB-C) filled with mortar, specimen(BRB-R) combined with a buckling restraint ring and Specimen(BRB-EP) filled with engineering plastics was fabricated, and a cyclic loading test was performed. As a result of the cyclic loading test, the maximum compressive strength, cumulative energy dissipation and ductility of each test specimen was similar. But in case of the cumulative energy dissipation and ductility, BRB-C filled with the mortar specimen showed the lowest. This is considered to be because the gap between the steel core and the reinforcing material for plastic deformation was not uniformly formed by pouring mortar around the core part.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.129-130
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• 2023

The compressive strength of concrete is greatly affected by the temperature inside the concrete at the initial age immediately after pouring. In the KCI Concrete Standard Specification, only the temperature correction strength (Tn) according to the curing temperature is applied in the mixing strength calculation formula, and mSn is not considered. The formula based on the Chrino model of the blast furnace slag concrete was calculated, and the strength of the structural concrete and the strength of the water cured specimen in the same mixture were compared with the predicted strength. As a result, the error between the predicted strength and the measured strength was greater in the structural concrete than in the concrete specimen.

• 한국주조공학회지
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• 제24권4호
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• pp.209-216
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• 2004

High silicon cast irons(HSCI) with the high acid resistance have been used for the prevention of acid corrosion occurring in various structures under acid conditions. However, the HSCI is only known as one of materials which have high acid resistance, but few work has dealt with this material in domestic. Therefore, in this study, the acid resistance of various cast irons with alloying elements and melting conditions have been examined, and studied the influences of the matrix structures, mechanical properties and morphologies of graphite. The results obtained in this study are as follows : In case of melting temperature, the mechanical properties of specimen manufactured with high temperature of $1650^{\circ}C$ showed higher value because the inclusion and impurity were removed. In case of pouring temperature, the mechanical properties of specimen fabricated below $1350^{\circ}C$ of pouring temperature showed higher value because the amount of gas absorption from atmosphere decreased during the solidification time. The corrosion rate decreased with increase in Si content. On the other hand, Mn addition appeared an opposite trend with Si.

• 한국해양공학회지
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• 제23권4호
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• pp.85-90
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• 2009

Although most of existing hydration heat control methods show a certain degree of hydration heat control, generally, there are many problems as mentioned above. Therefore, our laboratory previously developed a hydration heat control method using an exposed heat pipe, which solves most of these problems and simultaneously displays excellent hydration heat control. Unfortunately, even this method had some problems such as the processing, transport, and assembly of heat pipes, and the surface treatment of a cut plane after pouring, and hardening concrete. Therefore, in this study, a hydration heat control method using an embedded pipe has been developed with the expectation that this method solves those problems in hydration heat control using an exposed heat pipe. As a result of the experiment, the peak temperature of ECHP and ICHP specimen about $4.5{\sim}6.5^{\circ}C$ than the OPC specimen and the probability of thermal cracked generated in ECHP and ICHP specimen decreased up to $13{\sim}20%$. Finally, it was confirmed in this study that the hydration heat control method using an embedded heat pipe is significantly more superior and cost effective than the existing method of an exposed one.

• 대한치과의료관리학회지
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• 제11권1호
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• pp.38-46
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• 2023

Composite resins, commonly used in clinical practice, have been developed to improve aesthetics to obtain smooth surfaces. Although the restored composite resin has a smooth surface, it gradually becomes rough over time. Therefore, this study measured glossiness to evaluate the surface of various composite resins and attempted to evaluate the maintenance of glossiness of composite resins by observing surfaces that change to roughness. Specimens were produced using resin used in clinical practice: Gradia direct anterior (GA), Tetric N-Ceram (TN), Ceram.X Sphere TEC one (CX), Filtek Z350XT (FT), Estelite sigma quick (ES). After creating a smooth surface with slide glass, five locations were randomly selected to measure surface gloss, and the average was the representative value of the specimen. Roughness was applied to the specimen under water pouring at the same speed and pressure using SiC paper #2400, 1200, and 400. The gloss unit of different SiC papers was measured. To evaluate the gloss unit and gloss retention between composite resins, one-way analysis of variance and Tukey multiple comparisons test were used. As a result of the study, there was a difference in gloss unit of specimens produced under the same conditions. Although the degree differed depending on the composite resin, there was also a difference in gloss retention. Based on the findings, composite resins show differences in gloss due to their different characteristics. Ceram.X Sphere TEC one (CX) showing the lowest gloss retention and Estelite sigma quick (ES) showing the highest.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.836-841
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• 2005

As gravel roadbed is gradually turn down by repetitive loading of train, lasting work for maintenance and management of track is necessary to reduce the settlement of roadbed and the deterioration of track. Despite of above weak point, gravel roadbed has become a basic structure of roadbed at the present time. But request for new structure of roadbed is recently presented to settle an increased transportation capacity of track, and to solve a shortage of the labor to handle maintenance work of track. Therefore, we begin to research about maintenance-free roadbed like paved track from two years ago. In this study, a series of tests were performed to clarify the characteristics of strength and permeability of concrete specimen, which is the upper part of paved track injected by cement mortar, by type of geotextile and finally to give a basic data for application of geotextile to the lower part of paved track.

• 한국지반공학회논문집
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• 제29권7호
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• pp.37-46
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• 2013

실제 토목현장에 사용되는 토사에는 크고 작은 자갈이 포함된 경우가 많으며, 특히 도로 노반공사, 흙댐, 옹벽 뒤채움재 등에 사용되는 양질의 토사에도 소량의 자갈이 포함되어 있는 경우가 많다. 이럴 경우 소량의 자갈이지만 자갈의 함유량이나 크기에 따라 흙의 건조밀도가 크게 달라질 수 있으며, 이는 건조밀도를 이용한 다짐도 평가를 부정확하게 할 수 있다. 본 연구에서는 낙동강 모래에 크기가 다른 세 종류(2.0-2.36, 3.35-4.75, 5.6-10.0mm)의 자갈을 이용하여 자갈 함유량을 0, 10, 17, 23, 29, 33%로 달리하면서 다짐몰드 내에 다짐하거나 느슨하게 공시체를 제작한 다음 자갈섞인 공시체의 건조밀도 변화를 실험적으로 연구하였다. 자갈 함유량이 33%까지 증가함에 따라 최대건조밀도(또는 건조밀도)는 자갈의 크기에 따라 다짐된 공시체의 경우 15-20%, 느슨한 공시체의 경우 20-23%까지 증가하는 경향을 보였다. 자갈 함유량과 크기가 동일한 경우 느슨한 공시체보다 다짐한 공시체의 건조밀도가 $0.1-0.16g/cm^3$ 정도 더 높은 것으로 나타났다. 자갈 함유량은 동일하지만 작은 자갈(2.0-2.36mm)을 사용한 경우보다 큰 자갈(5.6-10.0mm)을 사용한 경우의 건조밀도가 다짐한 공시체의 경우는 $0.04-0.08g/cm^3$, 느슨한 공시체의 경우는 $0.03-0.05g/cm^3$ 정도 증가하였다.