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손병직,이상열,지효선 한국복합신소재구조학회 2014 복합신소재구조학회논문집 Vol.5 No.1
This study analyzes performance-cost ratio of composite(GFRP) wind-towers by fiber reinforcement angle and determines their optimal fiber angle. The finite element models for composite structures using the ANSYS program described in this paper is attractive not only because it shows excellent accuracy in analysis but also it shows the effect of the geometrical combination. New results reported in this paper are focused on the significant effects of the cost for various parameters, such as thicknesses of outer shells and stiffeners. From the numerical examples, optimal fiber angles were determined as 80° 90°.
영상처리를 이용한 인장시편의 손상면적 측정에 관한 연구
손병직,이규환,박원태 한국복합신소재구조학회 2016 복합신소재구조학회 학술발표회 Vol.2016 No.04
In this paper, we study the calculation for the damage area of the tension specimens using image processing techniques. This study was able to calculate the area of the damage region on the basis of original image. Generally, to extract the area in the original image, we have to use opening operation, close operation, the Hit-or-Miss operation and bottom hat filter, top hat filter, etc. In particular, to extract the area of the composite specimen discussed in this study, we have to use the combination of the operations and filters because it is non-isotropic material, or should develop a new algorithm based on it.
손병직,지효선,장석윤,Son, Byung-Jik,Ji, Hyo-Seon,Chang, Suk-Yoon 한국복합신소재구조학회 2012 복합신소재구조학회논문집 Vol.3 No.2
In this study, composite laminate cantilever type cylindrical shells with edge-stiffeners are analyzed. A versatile 4-node flat shell element which is useful for the analysis of shell structures is used. An improved flat shell element is established by the combined use of the addition of non-conforming displacement modes and the substitute shear strain fields. Two models by load conditions are considered. Load type A and B are loaded by point load at the free edge and line load respectively. A various parameter examples are presented to obtain proper stiffened length and stiffened thickness of edge-stiffeners. It is shown that the thickness of shell can be reduced minimum 30% by appropriate edge-stiffeners.
손병직,이규환 한국복합신소재구조학회 2017 복합신소재구조학회논문집 Vol.8 No.4
Deep learning techniques have been studied and developed throughout the medical, agricultural, aviation, and automotive industries. It can be applied to construction fields such as concrete cracks and welding defects. One of the best performing techniques of deep running is CNN technique. CNN means convolutional neural network. In this study, we analyzed crack recognition of sewer with low recognition. Deep learning is generally more accurate with deeper layers, but analysis cost is high. In addition, many variations can occur depending on training options. Therefore, this study performed many parametric studies according to the variations of training options. When analyzed with appropriate training options, the accuracy was over 90% and stable results were obtained
복합적층 원뿔형 쉘의 자유진동에 관한 기하학적 형상의 영향
손병직,지효선,장석윤,Son, Byung Jik,Ji, Hyo Seon,Chang, Suk Yun 한국강구조학회 2002 韓國鋼構造學會 論文集 Vol.10 No.4
쉘 구조물은 지붕 구조물, 굴뚝 구조물, 압력구조물, 선박구조물, 항공구조물 등에 널리 사용되는 구조물이다. 본 논문은 전단변형 효과를 고려한 비등방성 복합성층 원뿔형 쉘의 자유진동에 관하여 연구하였다. 복합재료는 2개 또는 이상의 재료들로 구성되어 구조적인 효율성을 증진시키도록 구성된 재료이다. 이러한 복합재료로 구성된 구조물의 거동은 매우 복잡하기 때문에 해석해를 구하기가 거의 불가능하다. 따라서 본 연구에서는 이러한 복합재료로 구성된 원뿔형 쉘의 자유진동을 해결하는데 유한차분법을 사용하였다. 중심각, 정점각 및 다른 기하학적 파라미터의 진동에 대한 효과를 연구하였고, 진동모드 형상을 예시함으로서 진동모드에 관한 물리적 및 공학적인 이해를 증진시키고자 하였다. Shell structures have become critical in the design of pressure vessels, submarine hulls, ship hulls, airplane structures, concrete roofs, containers for liquids, and many other structures. This study presented the feature of the free vibration of anisotropic laminated conical shells according to transverse shear deformation effects. Composite materials are composed of two or more different materials in order to produce desirable properties for structural strength. Since their behavior is very complex, it is almost impossible to solve the analytical solutions. This effects of subtended and vertex angles and other geometric parameters on vibration were investigated in a comprehensive parametric study. Selected vibration mode shapes were illustrated, to enable the physical understanding of vibration of laminated composite conical shells.
깊은 보의 스트럿-타이 모델과 고전적인 방법의 설계 비교
손병직 한국복합신소재구조학회 2013 복합신소재구조학회논문집 Vol.4 No.2
Deep beam shall be designed either by taking into account nonlinear distribution of strain or by Appendix A of Strut-and-Tie Models (STM) according to ACI 318(M) from version of 2002. Although STM is accepted as tool in design Discontinuity region (D-region) which mostly exist in Deep beam, Corbels, Dapped ends etc., it has been modified by many researchers. In this study we design deep beam by STMs which use simple truss for load distribution and the model of complex truss for load distribution compare with the ACI traditional which is designed by flexure design method and shear provided by concrete(Vc) as provided in special provisions section of 11.8 in ACI 318-99 [1]. This study aims to find the different and efficiency of deep beam design based on variation of parameter compiled from many samples selected from ACI traditional and two model of STMs, simple and complex load distribution.
손병직,최창호 한국복합신소재구조학회 2016 복합신소재구조학회논문집 Vol.7 No.3
Recent frequent occurrence of urban sinkhole brings a need for the periodic inspection of sewer pipelines. Sewer inspection using a CCTV device needs a lot of time and efforts. Many of previous studies which have focused to reduce the laborious tasks are mainly interested in the developments of image processing S/W and inspection H/W. Nevertheless, there has been no attempt to find meaningful information from the existing CCTV images stored by the sewer maintenance manager. In this paper, we carried out a study about the construction of unfolding image of sewer video image. In general, the analysis results show that the image development is judged to have been well represented. It is expected to be a reference to the basic research of panoramic image.
광섬유 매립형 센싱보강재의 BOTDR 계측신호 기반 시트보강공법 결함탐지 연구
손병직,김병철,김재환 한국복합신소재구조학회 2020 복합신소재구조학회논문집 Vol.11 No.4
자연재해 발생을 예방하기 위한 방재센서 기술이 중요하며 광섬유를 이용한 센서에 대한 관심이 높아지고 있다. 본논문은 광섬유 센서 내장 탄소섬유시트로 보강된 RC보의 계측된 데이터로 결함 탐지 연구를 수행하였다. 미분의 국부적 변동특성을 이용한 Method Ⅰ과 컨벌루션 방법을 이용한 Method Ⅱ를 비교, 분석하였다. 다른 차원의 데이터를 비교하기 위해서 무차원화 시켰으며, 분석 결과 Mehtod Ⅱ가 결함의 위치를 예리하게 잘 탐지하는 것으로 나타났다. Method Ⅱ인 컨벌루션에 사용되는 필터 벡터를 잘 응용하면 더 좋은 효과를 기대할 수 있을 것으로 판단된다. Sensor technology to prevent damage due to natural disasters is important, and interest in optical fiber sensors is increasing. In this paper, a damage detection study was performed using measurement data from a reinforced concrete beam reinforced by carbon fiber sheets embedded with optical fiber sensors. Method I using the local variation differential and Method II using the convolution method were compared and analyzed. In order to compare the data having different dimensions, it was first converted to a dimensionless quantity, and subsequent analysis showed that Method II sharply detects the location of damage. If the filter vector used in Method II is applied well, a better effect can be expected.