• Structural Engineering and Mechanics
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• 제67권3호
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• pp.267-275
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• 2018

A numerical study of soil-foundation system under monotonic and cyclic pushover loading is conducted, taking into account both material and geometric nonlinearities. A complete and refined 3D finite element (FE) model, using contact condition and allowing separation between soil and foundation, is implemented and used in order to evaluate the nonlinear relationship between applied vertical forces and induced settlements. Based on the obtained curve, a simplified model is proposed, in which the soil inelasticity is satisfactorily represented by two vertical springs with trilinear behavior law, and the foundation uplifting is insured by gap elements. Results from modeling soil-foundation system supporting a bridge pier have shown that the simplified model is able to capture irreversible settlements induced by cyclic rocking, due to soil inelasticity and vertical loading, as well as large rotations due to foundation uplifting.

• 한국공작기계학회논문집
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• 제17권4호
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• pp.140-145
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• 2008

Recently more complex geometric shapes, including freeform surfaces, are adopted for the design of products to emphasize style or beauty. Modeling of these products is extremely difficult or often impossible. Reverse engineering is the latest technology that can solve the problem by generating CAD models from the physical mockups or prototype models. Reverse engineering uses the coordinate measuring machine(CMM) to get the shape data of products. CMM is limited by the size of the product; therefore it must need the feature to solve it. The tooling-ball which is generally used for feature has difficulty in being used for soft products. Besides, the higher the accuracy of the tooling-ball is, the more expensive its cost is. This study will develop the feature of high accuracy without additional tools and compare the difference of accuracy by it.

• 한국측량학회지
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• 제26권2호
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• pp.165-173
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• 2008

본 연구는 라이다데이터와 수치지도를 이용하여 도로의 3차원 기하모델을 자동으로 생성하는 것을 목표로 한다. 도로모델을 생성하는 주요 과정은 (1) 수치지도의 도로경계 레이어를 이용하여 도로영역을 나타내는 다각형을 생성하고, (2) 다각형을 이용하여 도로영역내의 라이다 점을 추출하고, (3) 점을 표면패치로 분할하고, 표면패치를 그룹화 하여 다시 표면패치집단으로 구성하고, (4) 도로표면패치집단을 식별하고 여기에 포함된 점을 추출하여, 추출된 점을 이용하여 표면모델을 구성하고, (5) 도로경계선을 수치지도를 이용하여 정제한다. 제안된 방법을 실측데이터에 적용하여 도로의 선형 및 표면정보를 성공적으로 추출할 수 있었다

• 한국군사과학기술학회지
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• 제15권5호
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• pp.687-698
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• 2012

LADAR systems can rapidly acquire 3D point clouds by sampling the target surfaces using laser pulses. Such point clouds are widely used for diverse applications such as DSM/DTM generation, forest biomass estimation, target detection, wire avoidance and so on. Many kinds of LADAR systems have been developed with their respective purposes and applications. Particularly, Geiger mode imaging LADAR systems are increasingly utilized since they are energy efficient thank to extremely sensitive detectors incorporated into the systems. The purpose of this research is the performance assessment of a Geiger mode imaging LADAR system based on simulation with the real system parameters. We thus developed a simulation method of such a LADAR system by modeling its geometric, radiometric, optic and electronic aspects. Based on the simulation, we performed the performance assessment of a newly designed system to derive the outlier ratio and false alarm rate expected during its operation in almost real environment with reasonable system parameters. The proposed simulation and performance assessment method will be effectively utilized for system design and optimization, and test data generation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권1호
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• pp.74-89
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• 2021

For higher-level requirements of urban planning and management and the recent development of "digital earth" and "digital city", it is urgent to establish protocols for the construction of three-dimensional digital city models. However, some problems still exist in the digital technology of the three-dimensional city model, such as insufficient precision of the three-dimensional model, not optimizing the scene and not considering the constraints of building codes. In view of those points, a method to interactively simulate a virtual city scene based on building codes is proposed in this paper. Firstly, some constraint functions are set up to restrict the models to adhere to the building codes, and an improved directional bounding box technique is utilized to solve the problem that geometric objects may intersect in a virtual city scene. The three-dimensional model invocation strategy is designed to convert two-dimensional layouts to a three-dimensional urban scene. A Leap Motion hardware device is used to interactively place the 3D models in a virtual scene. Finally, the design and construction of the three-dimensional scene are completed by using Unity3D. The experiment shows that this method can simulate urban virtual scenes that strictly adhere to building codes in a virtual scene of the city environment, but also provide information and decision-making functions for urban planning and management.

• Ocean Systems Engineering
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• 제12권2호
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• pp.225-245
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• 2022

More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.

• 한국건설관리학회논문집
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• 제14권3호
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• pp.88-96
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• 2013

건설정보화의 다양한 노력 중, 최근 Building Information Modelling (BIM) 활용이 급속히 확대되고 있으며 그 활용 형태 또한 점차 '고도화' 및 '효율화'되고 있다. 그럼에도 불구하고, BIM 실무활용을 위해서 요구되는 다대한 추가 업무 부담은 BIM 실무적용의 가장 중요한 장애요인으로 지적되어 왔다. 이러한 맥락에서, 본 연구는 BIM 활용의 기능적인 '고도화'를 더욱 발전시키면서 동시에 이에 요구되는 업무 부담을 최소화시키는'효율화'를 연구목표로 설정하고, 이를 위한 핵심 요소기술로서, "BIM 객체 분류체계 (OBS)"를 정의하고 개발하였다. 본 연구에서 제안된 OBS는 BIM 도형정보의 각 객체별 식별번호를 목적에 부합한 규칙에 의해 부여함으로써, 비도형 정보(예로서 공정 및 원가)와의 연계를 용이케 하는 것을 목적으로 한다. 제안된 OBS 활용을 통하여 객체간의 물리적 위계 구성, 공정 액티비티 연계, 원가 정보 연계 등 다수 기능이 시스템화 되며, 따라서 다차원 CAD 구현을 위해 요구되는 지나치게 많은 데이터간의 연계 작업이 자동화됨으로써 BIM 실무구현의 현실성을 획기적으로 높일 수 있다. 제안된 OBS의 개념은 신한옥 주택 건설 사례를 통하여 적용 및 검증하였다.

• 한국측량학회지
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• 제27권3호
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• pp.393-400
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• 2009

최근 실세계를 재현하기 위한 3차원 기술개발의 필요성과 요구가 증가하게 되어 이러한 요구를 충족하기 위해 실세계 재현에 대한 연구가 국내외적으로 활발히 진행되고 있다. 기존에 구축된 공간분석을 위한 데이터는 2차원을 목적으로 제작되었으며 이는 3차원의 현실세계를 반영하는데 한계성이 있다. 또한 데이터 활용성이 제한적이며 데이터 재생산은 비용과 시간의 측면에서 비효율적이므로 기존의 데이터를 활용하여 효과적으로 3차원의 현실세계를 재현할 수 있는 방법에 대한 연구의 필요성이 증대되었다. DEM(Digital Elevation Model: 수치표고모델)은 활용 분야별로 다양한 요구조건을 만족하는 개별적인 방법으로 제작되어 활용되며 기존의 DEM 제작은 일률적인 보간법과 해상도로 제작되므로 데이터의 효율성이 떨어진다. 이는 실세계를 반영하기 위한 정확성에서의 한계성을 가지므로 다양한 데이터를 포함하면 효율성을 높일 수 있다. 본 연구에서는 지형분석을 통해 산악지, 구릉지, 평지로 분류 하여 서로 상이한 보간법과 해상도로 다중 해상도 DEM을 생성하였고 지형의 특성을 대표하는 model keypoint 데이터를 생성하여 포함하였다. 또한 3차원 공간정보를 포함하는 데이터 융합을 위해 도화원도와 통합하여 포괄적, 적응적 및 융통적 지형공간 데이터 모델링을 방안을 제안하였다.

• Journal of Computational Design and Engineering
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• 제3권4호
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• pp.322-329
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• 2016

The advent of high-performance terrestrial laser scanners has made it possible to capture dense point-clouds of engineering facilities. 3D shape acquisition from engineering facilities is useful for supporting maintenance and repair tasks. In this paper, we discuss methods to reconstruct box shapes and polygonal prisms from large-scale point-clouds. Since many faces may be partly occluded by other objects in engineering plants, we estimate possible box shapes and polygonal prisms and verify their compatibility with measured point-clouds. We evaluate our method using actual point-clouds of engineering plants.

• 대한기계학회논문집
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• 제18권12호
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• pp.3159-3174
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• 1994

A simple octree encoding algorithm based on a tetrahedron root has been developed to be used for fully automatic generation of three dimensional finite element meshes. This algorithm starts octree decomposition from a tetrahedron root node instead of a hexahedron root node so that the terminal mode has the same topology as the final tetrahedral mesh. As a result, the terminal octant can be used as a tetrahedral finite element without transforming its topology. In this part(I) of the thesis, an efficient algorithm for the tetrahedron-based octree is proposed. For this development, the following problems have been solved, : (1) an efficient data structure for storing the octree and finite elements, (2) an encoding scheme of a tetrahedral octree, (3) a neighbor finding technique for the tetrahedron-based octree.