• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.30-31
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• 2017

The objective of this study is to evaluate the performance of polymer-modified surface preparation mortars with pozzolanic materials for corrosion prevention method in deteriorated sewage treatment structures. The prepackaged-type surface preparation mortars are prepared with a polymer-binder ratio of 10%, ground granulated blast furnace slag contents of 0, 15, 30%, a fly ash content of 15%. And, the specimens are tested for workability, adhesion in tension, water absorption, crack and impact resistance. As a result, the prepackage-type surface preparation mortars for sewage treatment structure are satisfied with quality requirements by KS F 4716, Japan sewage work agency(JS) and JIS A 6916 for surface preparation mortars.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.166-173
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• 1998

The evaluation of joint fatigue strength of light weight materials for an electrical vehicle body has been performed through T-peel joint tests with the design parameters such as joint style, adherend type, adherend thickness, adhesive thickness, and various adhesives. Fatigue strength was evaluated through 5-Hz, tension-tension, load controlled test with the zero stress ratio. It was observed that the fatigue strength of the joint increases with the increase of the adherend thickness. With the increase of the adhesive thickness, however, the fatigue strength of the joint increases insignificantly. An aluminum-FRP adherend combination shows much higher fatigue strength than an aluminum-aluminum adherend combination. The results of fatigue tests were found to be consistent with those of static tests.

• 대한방사선기술학회지:방사선기술과학
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• 제3권1호
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• pp.43-48
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• 1980

An experimental study was carried out to make a comparison between tube voltage and density of barium sulphate in the stomach radiography. The results were summarized as follows: 1. The percentage of density on concentrations of barium sulphate as contrast media could not show in differences with changes of voltages applied X-ray tube. 2. The changes of density visualized on X-ray film mainly depend upon with thickness of stomach filled barium sulphate than the ratio of barium sulphite and plain water volume. 3. The lesions positioned in upper part within stomach exhibited their best discrimination performanance with depth in the low tube voltage, followed in order by the middle part and lower part. However, the discrimination performanance at the high tension radiography uniformly visualized over X-ray film without density in change.

• 대한토목학회논문집
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• 제44권5호
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• pp.603-613
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• 2024

This study evaluated the mechanical properties of high-tension performance biochar concrete, focusing on the effects of varying biochar cement replacement ratios (0 %, 1 %, 2 %, 3 %, 4 %, and 5 %). Mechanical properties, including compressive strength, tensile strength, and flexural strength, were tested. The results showed a general decrease in compressive strength with increasing biochar replacement, with significant reductions at 1 % to 3 % levels. PVA fiber reinforcement improved long-term compressive strength, particularly at higher biochar levels. Tensile and flexural strength also showed initial reductions with low biochar levels but improved at higher replacement levels. PVA fibers consistently enhanced tensile and flexural strength. SEM images confirmed the integration of biochar and PVA fibers into the cement matrix, enhancing microstructural density and crack resistance.

• Structural Engineering and Mechanics
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• 제75권5호
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• pp.621-631
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• 2020

A laboratory experiment is conducted is to investigate the behaviour of a low-mass-ratio and high aspect ratio flexible cylinder under vortex-induced vibration (VIV). A flexible cylinder with aspect ratio of 100 and mass ratio of 1.17 is towed horizontally to generate uniform flow profile. The range of Reynolds number is from 1380 to 13800. Vibration amplitude, in-line and cross-flow frequency response, amplitude trajectory, mean tension variation and hydrodynamic force coefficients are analyzed based on the measurement from strain gauges, load cell and CCD camera. Experimental results indicate that broad-banded lock-in region is found for the cylinder with a small Strouhal number. The frequency switches in the present study indicates the change of the VIV phenomenon. The hydrodynamic force responses provide more understanding on the VIV of a low mass ratio cylinder.

• 한국세라믹학회지
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• 제28권1호
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• pp.19-19
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• 1991

인장/비틀림 조합을력하에서 하중경로에 따른 Al₂O₃튜브 시편의 파괴거동을 조사하였다. 인장 후 비틀림을 한 하중경로(I)에서의 거시적인 균열의 전파방향과 파괴강도는 최대 주응력 파괴조건과 일치하였다. 전단응력(τ)/인장응력(σ)의 비가 일정한 하중경로(Ⅱ)에서의 거시적인 균열의 전파 방향은 최대 주응력 파괴조건과 일치한, 최대 주응력 파괴강도는τ/ σ의 비에 다라 일축인장 파괴 강도보다 증가 또는 감소하였다. Welbull 이론은 수누 비틀림에서의 최대 주응력 파괴 강도가 일죽이장 파괴강도보다 증가함은 예측하였으나, 하중경로(Ⅱ)에서 파괴 강도가 감소함은 예측할 수 없었다. 파괴강도가 일죽인장 파과강도보다 증가 또는 감소하는 현상은 미세조직의 관찰로 부터 미세결함면에 존재하는 전단응력이 파괴에 미치는 영향으로 설명하였다. 끝으로, 인위적 균열에서의 파괴 조건과 인장/비틀림 조합응력하의 Al₂O₃튜브 시편의 파괴 실험치에 근거한 새로운 경험식을 제안하였다. 제안된 파괴 조건식은 하중경로에 따른거시적인 균열의 전파방향과 파괴강도의 실험치와 잘 일치하였다.

• 대한기계학회논문집A
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• 제26권11호
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• pp.2287-2296
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• 2002

Most cracks in the structure occur under mixed mode loading and those fatigue crack propagation behavior heavily depends on the stress ratio. So, it is necessary to study the fatigue behavior under mixed mode loading as the stress ratio changes. In this paper, the fatigue crack propagation behavior was respectively investigated at stress ratio 0.1, 0.3, 0.5, 0.7 and we changed the loading application angle into 0$^{\circ}$, 30$^{\circ}$, 60$^{\circ}$ to apply various loading mode. The mode I and II stress intensity factor of CTS specimen used in this study was calculated by the displacement extrapolation method using FEM (ABAQUS). Using both the experiment and FEM analysis, we have concluded the relationship between crack propagation rate and stress intensity factor range at each loading mode due to the variation of stress ratio. Also, when the crack propagated under given stress ratio and loading mode condition, we have concluded the dominant factors of the crack propagation rate at each case.

• 한국강구조학회 논문집
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• 제8권4호통권29호
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• pp.3-17
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• 1996

The purpose of this paper is to investigate experimentally and theoretically the strength and deformation of K-joints in welded Warren-type square hollow structural section truss. There are 2 types in K-joints in K-joints having one compression bracing member and one tension bracing member. One type is KP-series that brae members are rotated to $45^{\circ}$, another type is KS-series that are not rotated. Principal parameters are the ratio of the chord width to thickness (D/T=33.3, 25, 16.7), the ratio of brace width to chord width(d/D=0.4, 0.5, 0.67, 0.83, 1.0) and the ratio of eccenticity to chord height (e/D=0.25, 0.125, 0, -0.125, -0.25, -0.375, -0.5). The important results obtained from the experiments are as follow ; The strength of K-joints increase proportionally as the D/T ratio decreases, and the d/D ratio increases. But the e/D ratio has no correlation with the strength of K-joints. Generally the strength and ductility ratio of KP-series increase more than a current type(KS-series) in full ${\beta}$range.

• Earthquakes and Structures
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• 제15권5호
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• pp.453-462
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• 2018

Damages to buildings affected by a near-fault strong ground motion are largely attributed to the vertical component of the earthquake resulting in column failures, which could lead to disproportionate building catastrophic collapse in a progressive fashion. Recently, considerable interests are awakening to study effects of earthquake vertical components on structural responses. In this study, detailed modeling and time-history analyses of a 12-story code-conforming reinforced concrete moment frame building carrying the gravity loads, and exposed to once only the horizontal component of, and second time simultaneously the horizontal and vertical components of an ensemble of far-field and near-field earthquakes are conducted. Structural responses inclusive of tension, compression and its fluctuations in columns, the ratio of shear demand to capacity in columns and peak mid-span moment demand in beams are compared with and without the presence of the vertical component of earthquake records. The influences of the existence of earthquake vertical component in both exterior and interior spans are separately studied. Thereafter, the correlation between the increase of demands induced by the vertical component of the earthquake and the ratio of a set of earthquake record characteristic parameters is investigated. It is shown that uplift initiation and the magnitude of tensile forces developed in corner columns are relatively more critical. Presence of vertical component of earthquake leads to a drop in minimum compressive force and initiation of tension in columns. The magnitude of this reduction in the most critical case is recorded on average 84% under near-fault ground motions. Besides, the presence of earthquake vertical components increases the shear capacity required in columns, which is at most 31%. In the best case, a direct correlation of 95% between the increase of the maximum compressive force and the ratio of vertical to horizontal 'effective peak acceleration (EPA)' is observed.

• 대한조선학회지
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• 제6권1호
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• pp.43-67
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• 1969

The effect of a circular hole reinforced by a ring of different material in a plate under biaxial loadings is considered. In this problem, an infinitely large flat is assumed. The reinforcing ring is of uniform rectangular cross-section of same thickness as the plate. The outer boundary of the ring is cemented to the inner boundary of the hole in the plate. The plate is subjected to hydrostatic tension and pure shear loadings. The stress distribution around the hole is obtained by means of the two dimensional theory of elasticity. To conform the validities of above solutions, a series of photo-elastic stress analysis for a composite model was carried out. Fair agreements were observed between two sets of values. The conclusions arrived at are as follows: 1) The theoretical solutions are exact ones for the case of infinitely large flat plate. 2) The solutions can be used for most case of engineering problem if the bonding between the plate and ring is perfect. 3) If the ratio of Young's moduli of the ring and the plate is increased, the stresses in the plate decrease whereas those in the ring increase. 4) The stress concentration near the hole has localized effect. 5) Under hydrostatic tension, maximum principal stress and maximum shear stress increase as the ratio of inner and outer diameters of the ring increases. 6) Under pure shear, the stresses depend upon angular orientations of the points and maximum principal stress and maximum shear stress appear at 45 degree. They increase as the ratio of inner and outer diameters of the ring increases.