• Korea-Australia Rheology Journal
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• 제17권4호
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• pp.157-164
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• 2005

Hydrodynamic characteristic of surfactant drag-reducing flows is still not fully understood. This work investigated the temperature and diameter effect on hydrodynamic characteristic of cationic surfactant drag reducing flows in pipes. Solution of oleyl bishydroxyethyl methyl ammonium chloride (Ethoquad O/12), 900 ppm, as a cationic surfactant and sodium salicylate (NaSal), 540 ppm, as a counter-ion was tested at 12, 25, 40, and $50^{\circ}C$ in pipes with diameter of 13, 25, and 40 mm. Drag reduction effectiveness of this surfactant solution was evaluated in 25 mm pipe from 6 to $75^{\circ}C$. Rheological characteristic of this solution was measured by stress control type rheometer with cone-and-plate geometry. Scale-up laws proposed by previous investigators were used to evaluate the flow characteristic of the solution. It was found that this surfactant solution has clear DR capability until $70^{\circ}C$. Result of this work suggested that temperature has a significant influence in changing the hydrodynamic entrance length of surfactant drag reducing flows. From rheological measurement, it was found that the solution exhibits Shear Induced Structure at all temperatures with different degree of peak viscosity and critical shear rate.

• 한국구조물진단유지관리공학회 논문집
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• 제18권3호
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• pp.101-107
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• 2014

구조물의 손상 추정은 동적응답신호로부터 고유주기와 모드형상을 구한 후 이를 역해석하여 손상위치와 손상정도를 파악함으로써 이루어 진다. 건축구조물의 경우 토목구조물에 비하여 구조형식이 복잡하고 비구조요소 및 노이즈 등의 영향으로 인하여 구조물 판별에 어려움이 있다. 동적응답신호를 이용한 건물의 손상추정에 관한 최근의 연구들은 손상추정을 위하여 민감도 또는 추정치 등 간접적 지표를 사용하고 있으나, 좀 더 합리적이고 명확한 손상추정을 위하여 운동방정식으로부터 직접 유도된 변수를 손상지수로 활용할 필요가 있을 것으로 판단된다. 따라서 본 연구에서는 전단형 건물의 운동방정식으로부터 직접 유도된 층강성 감소비를 손상지수로 하는 손상추정 방법을 제안하였다. 제안된 손상지수는 손상 전 모드형상과 손상 전 후 고유진동수 차이를 알면 구할 수 있다. 제안된 손상 추정방법을 수치해석예제에 적용한 결과 손상이 발생한 층에서 층강성 변화율이 (-)부호를 나타내었으며, 크기가 다른 층에 비하여 15배 정도 크게 나타나 전단형 건물의 손상 추정지수로서 활용될 수 있을 것으로 판단된다.

• Earthquakes and Structures
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• 제9권1호
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• pp.127-143
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• 2015

In conventional seismic design, structures are assumed to be fixed at the base. To reduce the impact of earthquake loading, while at the same time providing an economically feasible structure, minor damage is tolerated in the form of controlled plastic hinging at predefined locations in the structure. Uplift is traditionally not permitted because of concerns that it would lead to collapse. However, observations of damage to structures that have been through major earthquakes reveal that partial and temporary uplift of structures can be beneficial in many cases. Allowing a structure to move as a rigid body is in fact one way to limit activated seismic forces that could lead to severe inelastic deformations. To further reduce the induced seismic energy, slip-friction connectors could be installed to act both as hold-downs resisting overturning and as contributors to structural damping. This paper reviews recent research on the concept, with a focus on timber shear walls. A novel approach used to achieve the desired sliding threshold in the slip-friction connectors is described. The wall uplifts when this threshold is reached, thereby imparting ductility to the structure. To resist base shear an innovative shear key was developed. Recent research confirms that the proposed system of timber wall, shear key, and slip-friction connectors, are feasible as a ductile and low-damage structural solution. Additional numerical studies explore the interaction between vertical load and slip-friction connector strength, and how this influences both the energy dissipation and self-centring capabilities of the rocking structure.

• 대한토목학회논문집
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• 제29권4C호
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• pp.153-162
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• 2009

본 논문은 지반굴착으로 인해 발생된 인접지반에서의 진행성 지반변위가 구조물에 미치는 영향을 구조물 및 지반의 특성을 달리하면서 지반-구조물 상호작용이 고려된 상태에서 조사한 것이다. 지반굴착에 의해 발생된 진행성 지반변위에 노출된 4층 및 2층의 블록식구조물이 서로 다른 조건의 지반위에 위치할 때 발생되는 구조물 거동이 수치해석을 통해 조사된다. 수치해석을 위한 구조물은 소요전단 및 인장강도 이상의 응력이 발생할 때 구조물에 크랙이 발생될 수 있도록 모델링되었다. 굴착유발 진행성 지반변위에 노출된 4층 및 2층의 블록식구조물의 거동은 지반변위의 진행단계에 따라 조사되며, 이로부터 얻어진 거동특성은 구조물이 지반굴착의 최종단계에서 일어나는 지반변위에 일시에 노출될 때 발생하는 구조물의 거동특성과도 비교된다. 서로 다른 구조물 특성 및 지반조건을 가진 구조물이 진행성 지반변위 및 최종 지반변위에 노출될 때 발생하는 거동비교는 구조물에 발생한 크랙의 분포정도 및 변형크기를 고려하면서 조사되며, 이러한 비교로부터 얻어진 결과는 지반굴착으로 인해 유발되는 인접구조물의 손상을 제어하고 최소화하는데 필요한 정보를 제공한다.

• 한국정밀공학회지
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• 제22권4호
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• pp.107-112
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• 2005

In this study, the dynamic analysis is performed fur predicting the transmitted force to flexible human body induced by prototype HIF(High Impulsive force) device operation, which is partially assembled by major parts. A beam-mass model and a shear-structure model are used for the flexible mount structure and their dynamic behavior are investigated by experimental results under rigid/flexible mount conditions using a general purpose device. From the test result of prototype device in rigid mount condition, the transmitted force to human body which can not be measured directly, is estimated based on the proved mount structure model.

• 대한토목학회논문집
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• 제32권3C호
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• pp.121-127
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• 2012

본 논문은 터널건설로 인해 발생된 인접지반에서의 지반변위가 프레임구조물에 미치는 영향을 터널 시공조건(지반손실)을 달리하면서 조사한 것이다. 터널굴착에 의해 발생된 지반변위에 노출된 4층 오픈 프레임구조물과 블록으로 채워진 프레임구조물이 서로 다른 시공조건(지반손실)에 노출될 때 발생되는 구조물 거동을 수치해석을 통해 조사하였다. 오픈 프레임구조물은 탄성구조물로서 모델링 한 반면, 블록으로 채워진 프레임구조물은 소요전단 및 인장강도 이상의 응력이 발생할 때 구조물에 실제크랙이 발생할 수 있도록 모델링하였다. 터널굴착유발 지반변위에 노출된 두 서로 다른 프레임구조물의 거동 및 손상정도를 터널 시공조건에 따라 조사하였으며, 발생된 구조물의 거동 및 손상정도는 구조물에 발생한 변형, 크랙크기 및 분포를 고려하여 서로 비교하였다. 뿐만 아니라, 다양한 시공조건(지반손실)의 변화에 의해 구조물에 유발될 수 있는 손상정도의 크기를 손상도 예측기준(Son and Cording, 2005)을 사용하여 제시하였다. 이러한 결과들은 향후 터널굴착으로 인해 유발되는 인접 프레임구조물의 손상을 제어하고 최소화하는데 필요한 정보를 제공할 것이다.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.53-66
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• 2022

The main objective of the present research was investigating the effects of a floating wave barrier installed in front of an offshore jacket structure on the wave height, base shear, and overturning moment. A jacket model with the height of 4.55 m was fabricated and tested in the 402 m-long wave flume of NIMALA marine laboratory. The jacket was tested at the water depth of 4 m subjected to the random waves with a JONSWAP energy spectrum. Three input wave heights were chosen for the tests: 20 cm, 23 cm, and 28 cm. Two different cross sections with the same area were selected for the wave barrier: square and rhombus. Results showed that the average decrease in the jacket's base shear due to the presence of a floating wave barrier with square and rhombus cross section was 24.67% and 34.29%, respectively. The use of wave barriers with square and rhombus cross sections also resulted in 19.78% and 33.11% decrease in the jacket's overturning moment, respectively. Hence, it can be concluded that a floating wave barrier can significantly reduce the base shear and overturning moment in an offshore jacket structure; and a rhombus cross section is more effective than an equivalent square section.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.998-1001
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• 2011

The concrete track on bridge should be designed to effectively cope with the behavior of the bridge superstructure. For this purpose, in general, shear keys are designed to be installed at a certain intervals on the bridge deck, and the track slab is cast on these shear keys to transfer the load induced by the relative displacement between track and bridge. In this study, to apply the precast concrete slab track on bridge, a shear key structure and its effective installation method are presented. Also, the structural behavior of this shear key has been evaluated by the laboratory mock-up test.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 춘계학술대회
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• pp.97-99
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• 1996

Intracellular gradients of the free calcium concentration are thought to be critical for the localization of functional responses within a cell. The mechanism of mechanotransduction may be associated with the localized accumulation of calcium stores for shear stress-exposed endothelial cells. The distribution of the calcium stores and the formation of the stress fibers were investigated by the indirect double immunofluorescent staining method with the calreticulin antibody and rhodamine phalloidin under flow condition. The shear stress of steady flow reorganized the cytoskeleton structure including the bundling and translocation to focal contacts. The calcium stores translocated from the cytoplasm to the focal contacting area. Consequently. accumulation of the calcium stores may participate in the shear stress-induced cytoskeleton organization of endothelial cells.

• Structural Engineering and Mechanics
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• 제83권2호
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• pp.245-257
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• 2022

As the main lateral load resisting system in high-rise reinforced concrete structures, the mechanical performance of shear wall has a significant impact on the structure, especially for high-rise buildings. Steel corrosion has been recognized as an important factor affecting the mechanical performance and durability of the reinforced concrete structures. To investigate the effect on the seismic behaviour of corroded reinforced concrete shear wall induced by corrosion, analytical investigations and simulations were done to observe the effect of corrosion on the ultimate seismic capacity and drift capacity of shear walls. To ensure the accuracy of the simulation software, several validations were made using both non-corroded and corroded reinforced concrete shear walls based on some test results in previous literature. Thereafter, a parametric study, including 200 FE models, was done to study the influence of some critical parameters on corroded structural shear walls with boundary element. These parameters include corrosion levels, axial force ratio, aspect ratio, and concrete compressive strength. The results obtained would then be used to propose equations to predict the seismic resistance and drift capacity of shear walls with various corrosion levels.