• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.87-90
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• 2003

In Resin transfer molding (RTM), composite parts are produced by impregnation of a dry reinforcement with liquid matrix resin. Permeability is a key issue in this process. For thin parts, the resin flow in the thickness direction can be neglected. Therefore thin parts are considered as two-dimensional composites. However the resin flow through the thickness is important to thicker parts and we have to consider out-of-plane permeability. This work discusses a method to measure out-of-plane permeability. The flow rate and pressure drop across the porous media were measured. Also one dimensional form of Darcy's law is applied to calculate the out-of-plane permeability of various preforms. The flow is injected uniformly into layers of the preform. And a circular fiber mat with 6cm diameter was cut and flattened from cylindrical mandrel.

• 한국강구조학회 논문집
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• 제25권1호
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• pp.93-102
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• 2013

본 연구에서는 철근콘크리트 벽과 강판 콘크리트 벽이 서로 수직면의 이질접합 형태로 만나는 벽의 면외 휨 거동 특성을 검토하기 위하여, L형 실험체를 제작하고 휨 실험을 수행하였다. 실험 시, 실험체의 동적특성을 확인하기 위하여 Push 및 Pull 하중을 반복하는 싸이클 하중을 구현하고자 하였다. Push 하중에 의한 실험 결과, 실험체의 공칭강도를 초과하는 휨 성능을 발휘하였으며, 이에 따라 설계에 적용된 수직철근의 미겹침 이음길이의 타당성을 확인할 수 있었다. 한편, Pull 하중 가력 시에는 수직철근이 최대 내력을 발휘하기 전에 접합부 콘크리트에서 전단 파괴 거동이 나타나, 이에 대한 보강이 필요함을 확인하였다.

• 한국공작기계학회논문집
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• 제13권1호
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• pp.94-99
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• 2004

The global stiffnesses and vibration characteristics of vehicle structures are mainly influenced by local stiffnesses of the joint structures consisted of complicated thin-walled panels. In this paper, the parametric study for the stiffnesses of the center pillar-roof rail joint of vehicle structure is performed through the linear static analysis. The analysis result shows that the reinforcement panel much affects the joint stiffness of out-plane direction (i.e., z-direction). And also, the flange radius and width of the joint structure much affect the Joint stiffness of out-plane direction. The study shows that vehicle joint stiffnesses can be effectively determined in designing vehicle structure through the parametric study.

• Advances in concrete construction
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• 제6권1호
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• pp.1-13
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• 2018

An experimental investigation has been carried out on the use of an environmentally sustainable material, bamboo, in the construction of precast concrete structural wall panels. The strength and behaviour of three prototype bamboo reinforced concrete wall panel specimens under two-way in-plane action was studied. The specimens with varying aspect ratio and thinness ratio were tested to fail under a uniformly distributed in-plane load applied at an eccentricity of t/6. The aspect ratio of the specimens considered includes 1.667, 1.818 and 2 and the thinness ratio includes 12.5, 13.75 and 15. The influence of aspect ratio and thinness ratio of bamboo reinforced concrete wall panels, on its strength and behaviour was discussed. Varnished and sand blasted bamboo splints of 20 mm width and thickness varying from 8 to 15 mm were used as reinforcement in concrete. Based on the study, an empirical equation was developed considering the geometrical parameters of bamboo reinforced concrete wall panels for predicting its ultimate strength under two way in-plane action.

• Structural Engineering and Mechanics
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• 제51권3호
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• pp.413-431
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• 2014

By carrying out the experiment of eight pieces of brick masonry walls with pilaster strengthened by Glass fiber reinforced polymer (GFRP) and one piece of normal masonry wall with pilaster under low reversed cyclic loading, the failure characteristic of every wall is explained; Seismic performances such as hysteresis, stiffness and its degeneration, deformation, energy consumption and influence of some measures including strengthening means, reinforcement area proportion between GFRP and wall surface, "through-wall" anchor on reinforcement effects are studied. The test results showed that strengthening modes have little influence on stiffness, stiffness degeneration and deformation of the wall, but it is another thing for energy consumption of the wall; The ultimate load, deformation and energy consumption of the walls reinforced by glass fiber sheets was increased remarkably, rigidity and its degeneration was slower; Seismic performance of the wall which considers strengthening means, reinforcement area proportion between GFRP and wall surface, "through-wall" anchor at the same time is better than under the other conditions.

• 한국지진공학회논문집
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• 제10권5호
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• pp.73-83
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• 2006

이 연구의 목적은 면외방향으로 반복하중을 받는 철근콘크리트 벽식 교각의 지진거동을 파악하고 합리적이면서 경제적인 내진설계기준을 개발하는데 있다. 정확하고 올바른 성능평가를 위하여 신뢰성 있는 비선형 유한요소해석 프로그램을 사용하였다. 사용된 프로그램은 철근콘크리트 구조물의 해석을 위한 RCAHEST이다. 유한요소로서는 면내회전강성도를 갖는 4절점 평면 쉘요소가 사용되었다. 두께방향에 대한 철근과 콘크리트의 재료성질을 고려하기 위하여 층상화기법이 도입되었다. 재료적 비선형성에 대해서는 균열콘크리트에 대한 인장, 압축, 전단모델과 콘크리트 속에 있는 철근모델을 조합하여 고려하였다. 신뢰성 있는 실험결과와 비교를 통하여 이 논문의 제안방법이 면외방향으로 반복하중을 받는 철근콘트리트 벽식 교각의 내진성능평가에 적합한 방법임을 입증하고자 한다.

• Steel and Composite Structures
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• 제34권4호
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• pp.525-545
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• 2020

This paper presents a new structural system to use as retaining walls. In civil works, there is a general trend to use traditional reinforced concrete (RC) retaining walls to resist soil pressure. Despite their good resistance, RC retaining walls have some disadvantages such as need for huge temporary formworks, high dense reinforcing, low construction speed, etc. In the present work, a composite wall with only one steel plate (steel-concrete) is proposed to address the disadvantages of the RC walls. In the proposed system, steel plate is utilized not only as tensile reinforcement but also as a permanent formwork for the concrete. In order to evaluate the efficiency of the proposed SC composite system, an experimental program that includes nine SC composite wall specimens is developed. In this experimental study, the effects of different parameters such as distance between shear connectors, length of shear connectors, concrete ultimate strength, use of compressive steel plate and compressive steel reinforcement are investigated. In addition, a 3D finite element (FE) model for SC composite walls is proposed using the finite element program ABAQUS and load-displacement curves from FE analyses were compared against results obtained from physical testing. In all cases, the proposed FE model is reasonably accurate to predict the behavior of SC composite walls under out-of-plane loads. Results from experimental work and numerical study show that the SC composite wall system has high strength and ductile behavior under flexural loads. Furthermore, the design equations based on ACI code for calculating out-ofplate flexural and shear strength of SC composite walls are presented and compared to experimental database.

• 한국해양공학회지
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• 제17권5호
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• pp.39-47
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• 2003

A study of the structural strength evaluation on the doubler plate, considering various load cases that were subjected to in-plane and out of plane combined load, has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate for various load cases, elasto-plastic large deflection analysis is introduced, including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed, based on the results. In order to compare the doubler structure with the original strength of main plate, without doubler, simple formulas for the evaluation of the equivalent flat plate thickness are derived for each load case, respectively, based on the additional series of analysis of flat plate structure. Using these derived equations, the thickness change of an equivalent flat plate is analyzed according to the variation of various design parameters of doubler platesome design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas are discovered, and these relations are formulated for the future development of simple strength evaluation formula of general doubler plate structure.

• 한국지반공학회논문집
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• 제30권11호
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• pp.5-15
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• 2014

사면파괴로 인한 피해사례가 늘어남에 따라 사면을 안전하게 설계하고 시공하는 것은 대단히 중요하다. 현재 실무에서 주로 사용되는 한계평형해석은 간단한 계산에 의해 안전율을 산정할 수 있지만 활동면을 미리 가정한다는 단점이 있다. 한편 유한차분해석 시 전단강도감소기법을 이용하여 안전율 산정이 용이해짐에 따라 설계 시 이용되는 빈도가 점차 증가하고 있다. 따라서 본 연구에서는 두 가지 해석방법의 비교를 통해 합리적인 쏘일네일링 설계방안의 제안을 목적으로 한다. 이를 위해 평면파괴 예상구간에 쏘일네일링 보강 시 보강패턴에 따른 보강효과를 비교해보았다. 그 결과 네일의 각도와 간격에 따른 보강효과는 동일하게 나타났다. 하지만 네일 길이가 증가함에 따라 한계평형해석의 경우 안전율이 증가하였지만 유한차분해석의 경우 안전율의 변화가 없었다.

• Geomechanics and Engineering
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• 제14권1호
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• pp.71-81
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• 2018

Soils are mostly nonhomogeneous and anisotropic in nature. In this study, nonhomogeneity and anisotropy of soil are taken into consideration by assuming that the cohesion increases with depth linearly and also varies with respect to direction at a particular point. A three-dimensional rotational failure mechanism is adopted, and then a three-dimensional stability analysis of slope is carried out with the failure surface in the shape of a curvilinear cone in virtue of the limit analysis method. A quasistatic approach is used to develop stability charts in nonhomogeneous and anisotropic soils. One can easily read the safety factors from the charts without the need for iterative procedures for safety factors calculation. The charts are of practical importance to prevent a plane failure in excavation slope whether it is physically constrained or not. Then the most suitable location of piles within the reinforced slope in nonhomogeneous and anisotropic soils is explored, as well as the interactions of nonhomogeneous and anisotropic coefficients on pile reinforcement effects. The results indicate that piles are more effective when they are located between the middle and the crest of the slope, and the nonhomogeneous coefficient as well as the anisotropic coefficient will not only influence the most suitable location for piles but also affect the calculated safety factor of existing reinforced slope. In addition, the two coefficients will interact with each other on the effect on slope reinforcement.