• Title, Summary, Keyword: initial shape analysis

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A Study on the Shape Analysis of Cable-Dome Structures (케이블-돔 복합구조의 형상해석에 관한 연구)

  • 권택진;한상을;최옥훈
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.93-100
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    • 1998
  • The basic systems of spatial structures such as shells, membrane, cable-nets and tensegrity structure have been developed to create the large spaces without column. These structures may have large freedom in scale and form, and especially tensegrity structures are received much attention from the view points of their light weight and aesthetics. But There re some difficulties concerning structural stability, surface formation and construction method. One of the way to solve these problems reasonably is a combination of tensile members and rigid members. A structural system based on this concept is referred to as the "HTS ( Hybrid Tension Structure )". This is a type of flexible structural system which is unstable initially, because the cable material has little initial rigidity. As cable - dome hybrid structures is a type of HTS, the initial stress for the self- equilibrated system having stable state have to be introduced. To determine initial stress having stable state, the shape finding analysis is required before the stress - deformation analysis. In this paper, the primary objective is to derive the nonlinear finite element formula of cable and truss members considering geometric nonlinearity for shape finding of cable-dome, and to propose the method to decide the initial stress by the shape analysis of cable-dome hybrid structure with the self-equilibrated state.

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An Improved Initial Force Method for Determining the Initial Configuration of Suspension Bridges (현수교 시스템의 초기형상 결정을 위한 개선된 초기부재력법)

  • Kim, Min;Kim, Ho-Kyung;Kim, Moon-Young
    • Journal of Korean Society of Steel Construction
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    • v.23 no.2
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    • pp.237-247
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    • 2011
  • This paper presents an improved initial force method for determining the initial shape of suspension bridges. After determining the initial shape factors through the force equilibrium conditions of each hanging point, the initial force method was applied with the computed values, each node's coordinates, and unstrained lengths of the cable element as inputs. The unstrained length of each cable element was regarded as a fixed value in each iteration step, unlike in the typical initial force method. This method can be applied to 2D and 3D suspension bridge models. The validity of the present method was demonstrated by comparing the results of the numerical examples.

Adjustment of Initial Shape for Spoked Wheel Cable Structures Considering Retractable Membrane's Tension (개폐식 막 장력을 고려한 스포크-휠 케이블 구조의 설계 형상 조절 기법)

  • Ha, Hyeonju;Shon, Sudeok;Lee, Seungjae
    • Journal of the Korean Association for Spatial Structures
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    • v.19 no.1
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    • pp.109-116
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    • 2019
  • In this paper, the shape adjustment algorithm of the spoked wheel cable structures with retractable membrane system is studied. The initial tension of the membrane or cable is necessary to form the structure and its value is determined by the design shape. However, due to internal and external environmental influences, its shape may be different from the initial designed shape. In the case of the cable structures covered in this study, tension adjustment is necessary to maintain the designed shape because it influences the tension of the cable depending on the state of the retractable membrane. Therefore, we proposed an adjustment algorithm of an initial shape based on the force method. The effectiveness and validity of the methodology were examined through the applicable cable structures. The results of the shape adjustment analysis of the symmetric spoked wheel cable model were reliable and accurate results were obtained.

Blank Design in Sheet Metal forming Process Using the Rollback Method (롤백방법을 이용한 박판금속성형공정에서의 블랭크 설계)

  • 김종엽;김낙수;허만성
    • Transactions of Materials Processing
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    • v.8 no.5
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    • pp.454-464
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    • 1999
  • A new blank design method is proposed to predict the optimum initial blank shape in the sheet metal forming process. The rollback method for blank shape design takes the difference between the deformed blank contour and the target contour shape into account. the minimization object function R is proposed. Based on the method, a computer program composed of blank design module, FE-analysis module and mesh generation module is developed. The rollback method is applied to square cup, reentrant cross section, L-shaped cup drawing process with the flange of uniform size around its periphery to confirm its validity. The optimum initial blank shape is obtained from an arbitrary blank shape after several modifications. Good agreements are recognized between the numerical results and the published experimental results for initial blank shape and thickness strain distribution. It is concluded that the rollback method is an effective and convenient method for an optimum blank shape design.

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Impact of initial damage path and spectral shape on aftershock collapse fragility of RC frames

  • Liu, Yang;Yu, Xiao-Hui;Lu, Da-Gang;Ma, Fu-Zi
    • Earthquakes and Structures
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    • v.15 no.5
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    • pp.529-540
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    • 2018
  • The influences of initial damage paths and aftershock (AS) spectral shape on the assessment of AS collapse fragility are investigated. To do this, a four-story ductile reinforced concrete (RC) frame structure is employed as the study case. The far-field earthquake records recommended by FEMA P695 are used as AS ground motions. The AS incremental dynamic analyses are performed for the damaged structure. To examine the effect of initial damage paths, a total of six kinds of initial damage paths are adopted to simulate different initial damage states of the structure by pushover analysis and dynamic analysis. For the pushover-based initial damage paths, the structure is "pushed" using either uniform or triangle lateral load pattern to a specified damage state quantified by the maximum inter-story drift ratio. Among the dynamic initial damage paths, one single mainshock ground motion or a suite of mainshock ground motions are used in the incremental dynamic analyses to generate a specified initial damage state to the structure. The results show that the structure collapse capacity is reduced as the increase of initial damage, and the initial damage paths show a significant effect on the calculated collapse capacities of the damaged structure (especially at severe damage states). To account for the effect of AS spectral shape, the AS collapse fragility can be adjusted at different target values of ${\varepsilon}$ by using the linear correlation model between the collapse capacity (in term of spectral intensity) and the AS ${\varepsilon}$ values, and coefficients of this linear model is found to be associated with the initial damage states.

Analysis of Square Cup Deep Drawing from two Types of Blanks with a Modified Membrane Finite Element Method (개량박막 유한요소법에 의한 두가지 블랭크로부터의 사각컵 딥드로잉 성형해석)

  • Huh, Hoon;Han, Soo-Sik
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.10
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    • pp.2653-2663
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    • 1994
  • The design of sheet metal working processes is based on the knowledge about the deformation mechanism and the influence of the process parameters. The typical geometric process parameters are the die geometry, the initial sheet thickness, the initial blank shape, and so on. The initial blank shape is of vital importance in the most sheet metal forming operations, especially in the deep drawing process, since the forming load and the strain distribution are significantly affected by the shape of an initial blank. The influence of the initial blank shape on a square cup deep drawing process is investigated by the numerical simulation and the experiment. The numerical simulation is carried out by a modified membrane finite element method which takes bending deformation into account. The numerical and experi-mental results show that the initial blank shape have strong influence on the forming load and the strain distribution. The numerical results are compared with the experimental results and other numerical results which are calculated with the membrane theory.

Shape Finding and Stress Finding for Pneumatic Membrane Structures by Dynamic Relaxation Method (동적이완법에 의한 공기막구조물의 형태탐색과 응력해석)

  • 문창훈;이경수;배종효;최옥훈;한상을
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.268-275
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    • 1999
  • The purpose of this study is to propose the method of determining the initial pneumatic membrane structures surface and stresses and displacements. Tension structure such as pneumatic membrane structures is stabilized by their initial prestress and air pressure. The process to find initial structural overall shape of tension structures produced by initial prestress called shape finding. One of the most important factor for the design of membrane structures is to search initial smooth surface, because unlike steel or concrete building elements which resist loads in bending, all tension structure forces are carried within the surface by membrane stress. The result for initial surface of pneumatic membrane element and maximum displacement in large deformation in analysis is compared with well-known nonlinear numerical method such as Newton-raphson method and dynamic relaxation method

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Effect of Initial Defects on Welding Deformation and Residual Stress (강판의 초기不整이 용접변형.잔류응력에 미치는 영향)

  • 박정응
    • Journal of Welding and Joining
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    • v.17 no.4
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    • pp.76-84
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    • 1999
  • The residual stress generated when the steel plates were produced, did not influence on the out-of-plane deformation and residual stress generated by welding. When the initial deflection shape was a concave(Type I), the out-of-plane deformation became the same shape as that of the initial deflection and its magnitude became small. When the initial deflection made a winding in the welding direction(Type III), the out-of-plane deformation became large in the plate width. The initial deflection shape did not influence on residual stress and plastic strain produced by welding.

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Shape Design Optimization using Isogeometric Analysis Method (등기하 해석법을 이용한 형상 최적 설계)

  • Ha, Seung-Hyun;Cho, Seon-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.216-221
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    • 2008
  • Shape design optimization for linear elasticity problem is performed using isogeometric analysis method. In many design optimization problems for real engineering models, initial raw data usually comes from CAD modeler. Then designer should convert this CAD data into finite element mesh data because conventional design optimization tools are generally based on finite element analysis. During this conversion there is some numerical error due to a geometry approximation, which causes accuracy problems in not only response analysis but also design sensitivity analysis. As a remedy of this phenomenon, the isogeometric analysis method is one of the promising approaches of shape design optimization. The main idea of isogeometric analysis is that the basis functions used in analysis is exactly same as ones which represent the geometry, and this geometrically exact model can be used shape sensitivity analysis and design optimization as well. In shape design sensitivity point of view, precise shape sensitivity is very essential for gradient-based optimization. In conventional finite element based optimization, higher order information such as normal vector and curvature term is inaccurate or even missing due to the use of linear interpolation functions. On the other hands, B-spline basis functions have sufficient continuity and their derivatives are smooth enough. Therefore normal vector and curvature terms can be exactly evaluated, which eventually yields precise optimal shapes. In this article, isogeometric analysis method is utilized for the shape design optimization. By virtue of B-spline basis function, an exact geometry can be handled without finite element meshes. Moreover, initial CAD data are used throughout the optimization process, including response analysis, shape sensitivity analysis, design parameterization and shape optimization, without subsequent communication with CAD description.

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Novel Mesh Regeneration Method Using the Structural Deformation Analysis for 3D Shape Optimization of Electromagnetic Device (전자소자의 3차원 형상최적화를 위한 구조변형 해석을 이용한 새로운 요소망 변형법)

  • Yao Yingying;Jae Seop Ryu;Chang Seop Koh;Dexin Xie
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.52 no.6
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    • pp.247-253
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    • 2003
  • A novel finite element mesh regeneration method is presented for 3D shape optimization of electromagnetic devices. The method has its theoretical basis in the structural deformation of an elastic body. When the shape of the electromagnetic devices changes during the optimization process, a proper 3D finite element mesh can be easily obtained using the method from the initial mesh. For real engineering problems, the method guarantees a smooth shape with proper mesh quality, and maintains the same mesh topology as the initial mesh. Application of the optimum design of an electromagnetic shielding plate shows the effectiveness of the presented method.