• 한국강구조학회 논문집
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• 제14권5호통권60호
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• pp.567-576
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• 2002

중심 및 2축편심압축에 대한 고강도콘크리트충전 각형강관기둥에 대해 실험 및 해석을 수행하며, 실험변수는 기둥의 좌굴길이대 단면폭의 비 $L_k/D$, 편심의 크기 e, 그리고 편심하중의 각 ${\theta}$이다. 실험을 통하여 2축휨을 받는 고강도콘크리트충전 각형강관기둥의 내력 및 거동을 조사한 결과, 2축편심압축력을 받는 CFT기둥의 실험에 의한 최대내력 및 거동은 해석에 의한 값과 비교적 잘 일치하였다.

• Advances in concrete construction
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• 제13권 2호
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• pp.163-181
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• 2022

To study the mechanical properties of steel reinforced recycled concrete (SRRC) filled circular steel tube columns under eccentric compression loads, this study presents a finite element model which can simulate the eccentrically compressed columns using ABAQUS software. The analytical model was established by selecting the reasonable nonlinear analysis theory and the constitutive relationship of materials in the columns. The influences of design parameters on the eccentric compressive performance of columns were also considered in detail, such as the diameter-thickness ratio of circular steel tube, replacement percentage of recycled coarse aggregate (RCA), slenderness ratio, eccentricity, recycled aggregate concrete (RAC) strength and steel strength and so on. The deformation diagram, stress nephogram and load-displacement curves of the eccentrically compressed columns were obtained and compared with the test results of specimens. The results show that although there is a certain error between the calculation results and the test results, the error is small, which shows the rationality on the numerical model of eccentrically compressed columns. The failure of the columns is mainly due to the symmetrical bending of the columns towards the middle compression zone, which is a typical compression bending failure. The eccentric bearing capacity and deformation capacity of columns increase with the increase of the strength of steel tube and profile steel respectively. Compared with profile steel, the strength of steel tube has a greater influence on the eccentric compressive performance of columns. Improving the strength of RAC is beneficial to the eccentric bearing capacity of columns. In addition, the eccentric bearing capacity and deformation capacity of columns decrease with the increase of replacement percentage of RCA. The section form of profile steel has little influence on the eccentric compression performance of columns. On this basis, the calculation formulas on the nominal eccentric bearing capacity of columns were also put forward and the results calculated by the proposed formulas are in good agreement with the test values.

• Steel and Composite Structures
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• 제48권1호
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• pp.89-102
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• 2023

This study investigates the eccentric performance of concrete-filled steel tubular (CFST) stub columns strengthened with steel tube and sandwiched concrete (STSC) jackets. It was revealed that the STSC jacketing method effectively weakened the cracking of concrete in CFST columns on the convex side and the crash on the concave side. Substantial increases in the eccentric bearing capacities were demonstrated after strengthening. A numerical study was further conducted. The decrease in diameter-to-thickness ratio and increase in strength of outer tube contributed to increase in peak load of all components, whereas the increase in sandwiched concrete strength resulted in load increase on itself and had negligible effects on other components. The parametric study showed the effect of inner concrete strength on columns' bearing capacity was magnified after strengthening, whereas that of inner tube thickness was reduced. Within the parameters investigated, high-strength concrete and high-strength steel can be applied without the concern of early abrupt failure of inner low-strength concrete or steel tube.

• 한국강구조학회 논문집
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• 제14권6호
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• pp.823-834
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• 2002

Steel-Concrete Column은 H형강의 플랜지 사이에 후프를 용접하고 플랜지 사이의 공간에 콘크리트가 채워진 새로운 합성기둥이다. 본 연구에서는 이 새로운 합성 기둥의 구조성능을 평가하기 위하여 단주압축, 휨, 전단실험을 수행하였다. 각 실험별 실험체들을 순철골 실험체와 철골 콘크리트 실험체로 구성하여 Steel-Concrete Column을 구성하는 철골, 내부 콘크리트, 후프의 내력기여도를 평가할 수 있도록 하였다. 실험결과 Steel-Concrete Column은 $\ulcorner$강구조 한계상태 설계 기준$\lrcorner$ 에 의해 계산된 내력값을 충분히 만족하여 구조부재에 적용 가능하다고 판단된다.

• 대한통합의학회지
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• 제10권2호
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• pp.115-123
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• 2022

Purpose : The hamstring is a group of three muscles, biceps femoris, semitendinosus, and semimembranosus, placed behind the thigh. The hamstring is one of the most commonly injured muscles and usually occurs during high-speed, high-intensity exercise. The purpose of this study was to investigate the effect of static stretching and eccentric exercise of hamstrings on flexibility, strength, and functional performance. Methods : This study was conducted on 28 healthy adults. Subjects were divided into a static stretching group (n=15) and an eccentric exercise group (n=13). Subjects measured hamstring flexibility (active knee extension test), hamstring strength (concentric and eccentric peak torque), and functional performance (triple hop for distance and modified 20 m sprint). The intervention was conducted three times a week for six weeks. To compare the difference between values before and after the intervention, paired t-test was used, and an independent t-test was used to compare between groups. Results : In both groups, the active knee extension test, concentric peak torque, triple hop test, and 20 m sprint significantly increased after the intervention compared to before the intervention (p<.05). However, no significant difference was found in eccentric peak torque after intervention in both groups (p>.05). No significant difference was found between the two groups in the effect on the variables (p>.05). Conclusion : Both interventions were found to be effective for flexibility, concentric strength, and functional performance. Eccentric exercise and static stretching are recommended to improve the flexibility and functional performance of the hamstring. This study's results will be considered essential data on the effectiveness of static stretching and eccentric exercise.

• 콘크리트학회논문집
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• 제16권2호
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• pp.229-240
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• 2004

불균형 휨모멘트를 재하받는 플랫플레이트-기둥 접합부의 편심전단강도와 모멘트강도를 규명하기 위해 그동안 많은 실험연구가 수행되어 왔다. 기존 실험들은 서로 다른 실험방식을 사용하고 있는데, 접합부의 전단강도는 실험방식에 따라 차이가 있는 것으로 나타났다. 따라서 기존 실험에 근거하여 개발된 현행 설계기준들은 플랫플레이트의 강도를 정확히 설명하고 있지 못한 실정이다. 선행 연구에서는 연속 플랫플레이트에 대한 비선형 유한요소해석에 근거하여, 슬래브-기둥 접합부에 패한 새로운 설계방법을 개발하였다. 그러나 제안된 설계방법에서는 휨모멘트 강도산정에 필요한 접합부 편심강도를 경험식에 의존하여 산정하고 있다. 본 연구에서는, 접합부 파괴 메카니즘을 분석하기 위해서, Rankine 재료파괴기준을 이용하는 이론적인 접근법을 채택하였다. 분석결과에 근거하여 개선된 편심전단강도모델이 개발되었고, 기존 실험과의 비교를 통해 검증되었다. 개발된 강도식을 이용하여, 선행연구에서 개발된 설계방법을 재검증하였다.

• Steel and Composite Structures
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• 제42권5호
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• pp.617-631
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• 2022

To study the eccentric compressive performance of the basalt-fiber reinforced recycled aggregate concrete (BFRRAC)-filled circular steel tubular stub column, 8 specimens with different replacement ratios of recycled coarse aggregate (RCA), basalt fiber (BF) dosage, strength grade of recycled aggregate concrete (RAC) and eccentricity were tested under eccentric static loading. The failure mode of the specimens was observed, and the relationship curves during the entire loading process were obtained. Further, the load-lateral displacement curve was simulated and verified. The influence of the different parameters on the peak bearing capacity of the specimens was analyzed, and the finite element analysis model was established under eccentric compression. Further, the design-calculation method of the eccentric bearing capacity for the specimens was suggested. It was observed that the strength failure is the ultimate point during the eccentric compression of the BFRRAC-filled circular steel tubular stub column. The shape of the load-lateral deflection curves of all specimens was similar. After the peak load was reached, the lateral deflection in the column was rapidly increased. The peak bearing capacity decreased on enhancing the replacement ratio or eccentric distance, while the core RAC strength exhibited the opposite behavior. The ultimate bearing capacity of the BFRRAC-filled circular steel tubular stub column under eccentric compression calculated based on the limit analysis theory was in good agreement with the experimental values. Further, the finite element model of the eccentric compression of the BFRRAC-filled circular steel tubular stub column could effectively analyze the eccentric mechanical properties.

• Steel and Composite Structures
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• 제18권4호
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• pp.833-852
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• 2015

Self-compacting Concrete Filled steel Tubes (SCFT), which combines the advantages of steel and concrete materials, can be applied to strengthen the RC columns. In order to investigate the eccentric loading behavior of the strengthened columns, this paper presents an experimental and numerical investigation on them. The experimental results showed that the use of SCFT is interesting since the ductility and the bearing capacity of the RC columns are greatly improved. And the performance of strengthened columns is significantly affected by four parameters: column section type (circular and square), wall thickness of the steel tube, designed strength grade of strengthening concrete and initial eccentricity. In the numerical program, a generic fiber element model which takes in account the effect of confinement is developed to predict the behavior of the strengthened columns subjected to eccentric loading. After the fiber element analysis was verified against experimental results, a simple design formula based on the model is proposed to calculate the ultimate eccentric strength. Calibration of the calculated results against the test results shows that the design formula closely estimates the ultimate capacities of the eccentrically compressed strengthened columns by 5%.

• 운동영양학회지
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• 제23권1호
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• pp.48-54
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• 2019

[Purpose] The combined effect of different types of post-exercise treatment has not been fully explored. We investigated the effect of combined cold water immersion (CWI) and compression garment (CG) use after maximal eccentric exercise on maximal muscle strength, indirect muscle damage markers in the blood, muscle thickness, and muscle soreness score 24 h after exercise. [Methods] Ten men performed two trials (CWI + CG and CON) in random order. In the CWI + CG trial, the subjects performed 15 min of CWI (15℃), followed by wearing of a lower-body CG for 24 h after exercise. In the CON trial, there was no post-exercise treatment. The exercise consisted of 6 × 10 maximal isokinetic (60°·s^-1) eccentric knee extensions using one lower limb. The maximal voluntary contraction (MVC) and maximal isokinetic (60°·s^-1) strength during knee extension, as well as the indirect muscle damage markers, were evaluated before exercise and 24 h after exercise. [Results] The maximal muscle strength decreased in both trials (p < 0.001), with no difference between them. The exercise-induced elevation in the myoglobin concentration tended to be lower in the CWI + CG trial than in the CON trial (p = 0.060). The difference in the MVC, maximal isokinetic strength, muscle thickness, and muscle soreness score between the trials was not significant. [Conclusion] CWI followed by wearing of a CG after maximal eccentric exercise tended to attenuate the exercise-induced elevation of indirect muscle damage markers in the blood.

• Structural Engineering and Mechanics
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• 제91권5호
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• pp.517-526
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• 2024

Due to the asymmetric cross-section of unequal-angle steel, the application of loads can induce axial rotation, leading to a series of buckling failure behaviors. Special attention must be paid during the design process. The present study aims to analyze the structural behavior of asymmetric steel angle members under various eccentric loading conditions, considering the complex biaxial bending interaction that arises when the angle steel is connected to the panel. Several key factors are investigated in this paper, including the effects of uniaxial and biaxial eccentricity on the structural behavior and the eccentric axial compression strength of long and short legs at different load application points. Potential risks associated with the specified load points, based on the AISC specifications, are also discussed. The study observed that the strength values of the members exhibited significant changes when the eccentric load deviates from the specified point. The relative position of the eccentric load point and the slenderness ratio of the member are critical influencing factors. Overall, this research intends to enhance the accuracy and reliability of strength analysis methods for asymmetric single angle steel members, providing valuable insights and guidance for a safer and more efficient design.