• Journal of Korean Association for Spatial Structures
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• v.8 no.2
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• pp.105-113
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• 2008

Shell-typed structures can make resistance to external forces efficiently, and have merits to construct the large-span structures with thin thickness. This merits are highly depending on the shape of structure. Therefore designers want to the optimum shape, but it is not so easy to find the shape. So far there are many schemes to find more optimum shape, and those methods have their own characteristics. In this study, the authors introduce a relatively easy approach to find optimum shape by the finite element method considering geometric nonlinearity. We are finding the optimum shape of a shell-typed structure using line elements, and compared the results by various analytic models.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.2
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• pp.117-123
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• 2013

As fiber reinforced polymer (FRP) material is appled for a curved structure such as tunnel, FRP material must has a curved shape. Until now, the curved FRP material has been producted by hand-lay-up or filament winding work. It is impossible for mass production of the curved FRP material by these methods. Also, the quality of product by these methods is lower than that by pultrusion method. New pultrusion method and equipment had been developed for production of FRP material with steady curvature. The objective of this study is to evaluate the effect of freezing and thawing on adhesion of cement concrete with coarse-sand coated FRP in repair and reinforcement of cement-concrete structure using curved FRP material.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.43-52
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• 1990

Theoretical foundation and algorithms are presented of a new surface modeling and pre-processing system for the three-dimensional structures. The modeling method is based on the boundary representation scheme and composed of two hierarchical model structures: curve-network and surface models. The concept of modeling curve as a union of links is introduced to facilitate surface modeling via various transfinite mapping techniques or Coons Patches. Efficiency and novel aspects of the present method are discussed. Finite element mesh genceration and application procedures will be reported in a later paper.

• Journal of the Korea institute for structural maintenance and inspection
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• v.2 no.4
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• pp.172-176
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• 1998

강관 등과 같이 곡면을 이루는 구조물 용접부의 내부 결함을 검출하기 위한 기법을 제안하였다. 인공 결함을 만들어 초음파 비파괴검사를 행하고, 곡면의 표면 거리($Y_s$)를 계산하여 실측한 참값($Y_T$)과 비교해 보았다. 제안된 방법으로 계산한 값이 참값에 대하여 1%이하의 오차 범위에 들어오므로 강관 용접부의 내부 결함 검사에 응용될 수 있다.

• Composites Research
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• v.31 no.5
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• pp.246-250
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• 2018

In this paper, laser ultrasonic rotation scanning method was proposed to inspect and visualize defects in corner section of curved composite structure. L-shaped composite specimen with defects in its corner section were inspected using laser ultrasonic rotation scanning method. L-shaped specimens had artificial defects at three different depths to simulate delamination damage. All artificial defects were detected clearly in different time-of-flight according to their depths. Inspection result showed that the proposed method is suitable to inspect round corner section of curved composite structure without any special tools.

• 대한공업교육학회지
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• v.35 no.2
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• pp.224-237
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• 2010

When the underwater structure sails high speed, noise and vibration propagate to the sensor in the nose of the dome. In this paper, to avoid this kind of noise and vibration CRP(Carbon Reinforced Plastic) material and SNORE ring(Self-NOise REduction Ring) are attached at the curved structure and simulates its isolation characteristics using commercial software. Vibration displacement and stress are calculated at the planar sensor array. The material of the curved structure is aluminum and maximum outer diameter is 53Omm, 215mm in length, 270mm in planar diameter, respectively. Based on the simulation results, reduction ratio of the received normal stress at the sensor is above 95% at the frequency of 12kHz and 15kHz. At the mid point of the planar sensor the normal stress is higher than 20mm and 40mm apart. This results can be used to increase the sensitivity of the acoustic sensor as a basic data.

• Journal of Korean Association for Spatial Structures
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• v.7 no.2 s.24
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• pp.115-124
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• 2007

The initial shape is arrived at by a self-formation process, which accomplishes a form in the natural world, or is determined analytically by considering the equilibrium of initial stress only. Therefore, the self-formation process, which accomplishes a form in the natural world is grasped and the types of modeling techniques available to find the shapes of soft structures are well investigated and classified. To establish a form-finding modeling techniques, the models of string, soap film, fabric, rubber, plaster, and etc. are used. These modeling techniques can be used as a method of understanding the characteristics of structures when the material of model shows similar characteristics. Generally, the model test confirms the structure based on numerical analysis, at the same time it is important preceding process to develop such a program. With the above process, the relationship between model test and numerical analysis becomes a feedback process. Therefore, in this study, two examples which have been accomplished from such a technique are investigated and considered according to modeling process.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.62-62
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• 2004

최근 신소재인 선진 복합 재료 중 탄소 섬유 강화 플라스틱(이하 CFRP라고 한다. )은 비강도, 비강성이 높기 때문에 경량화가 요구되는 여러 분야, 즉 항공기, 인공위성, 원자로, 자동차 산업분야, 조선 산업분야 등 널리 사용되고 있다. 경량화가 요구되는 분야에 사용되는 구조 부재의 형상은 평판보다는 다양한 형태의 곡면 형상을 뛰는 챌(Shell)의 형상을 갖는다. 또한 이러한 구조물에 충격이 가해 졌을 때 곡면을 갖는 구조물의 충격_응답 및 파괴형태는 평판과는 다른 양상을 보인다.(중략)

• Journal of Korean Association for Spatial Structures
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• v.12 no.1
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• pp.77-85
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• 2012

The membrane structure maintains stable form by giving initial tension to ductile membrane and increasing the stiffness of exterior that is much adopted in the large span spatial structure by making its thickness thin. This kind of membrane structure has characteristic that can express free-form curve, so the selection of structural form is very important. So, this paper proposes the expression of free-form surface based on NURBS basis function and the finite element method considering geometrical nonlinearity for the deduction of large deformation result. Also, for minimizing the approximation of the surface that is derived from the form-finding result, the interface method that change finite element mesh to NURBS is proposed. So, the optimum surface of free-form membrane is derived.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.6
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• pp.451-461
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• 2010

Utilization of the fiber reinforced polymer (FRP) material has been enlarged as a substitution material to the general construction materials having certain long-term problems such as corrosion, etc. However, it could be difficult to apply the FRP material, which has a linear shape generally, to an arch-shaped tunnel structure. Therefore, an attempt has been made in this study to develop a device to form a designed cross section of FRP material by pulling out with a curvature. A sample of the circled FRP product was successfully produced and then the sample has been tested to identify its physical characteristics. Then, intensive feasibility studies on the circled FRP panel to be used for a tunnel lining structure have been carried out by numerical analyses. As a result, it appears that the new circled FRP-concrete composite panel has a high capability to be used for a tunnel lining material without any structural problem.