• Title, Summary, Keyword: initial shape analysis

Search Result 520, Processing Time 0.036 seconds

Investigation on deck-stay interaction of cable-stayed bridges with appropriate initial shapes

  • Liu, Ming-Yi;Lin, Li-Chin;Wang, Pao-Hsii
    • Structural Engineering and Mechanics
    • /
    • v.43 no.5
    • /
    • pp.691-709
    • /
    • 2012
  • This paper provides a variety of viewpoints to illustrate the mechanism of the deck-stay interaction with the appropriate initial shapes of cable-stayed bridges. Based on the smooth and convergent bridge shapes obtained by the initial shape analysis, the one-element cable system (OECS) and multi-element cable system (MECS) models of the Kao Ping Hsi Bridge in Taiwan are developed to verify the applicability of the analytical model and numerical formulation from the field observations in the authors' previous work. For this purpose, the modal analysis of the two finite element models are conducted to calculate the natural frequency and normalized mode shape of the individual modes of the bridge. The modal coupling assessment is also performed to obtain the generalized mass ratios among the structural components for each mode of the bridge. The findings indicate that the coupled modes are attributed to the frequency loci veering and mode localization when the "pure" deck-tower frequency and the "pure" stay cable frequency approach one another, implying that the mode shapes of such coupled modes are simply different from those of the deck-tower system or stay cables alone. The distribution of the generalized mass ratios between the deck-tower system and stay cables are useful indices for quantitatively assessing the degree of coupling for each mode. These results are demonstrated to fully understand the mechanism of the deck-stay interaction with the appropriate initial shapes of cable-stayed bridges.

A Study on the Stress Concentration at Crack of Membrane Structures (막구조물의 파손단면에서의 응력집중 현상에 관한 연구)

  • Jeon, Jin-Hyung;Jeong, Eul-Seok;Kim, Seung-Deog
    • Proceeding of KASS Symposium
    • /
    • /
    • pp.89-98
    • /
    • 2005
  • Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The material property of the membrane has strong axial stiffness, but little bending stiffness. Therefore membrane structures arc unstable structures initially. These soft structures need to be introduced initial stresses first because of its initial unstable state, and it happens large deformation phenomenon. To find the structural shape after large deformation caused by initial stiffness introduced, we need the shape analysis considering geometric nonlinearity in structural design procedure. In this study, we investigate into the stress concentration at crack of membrane structures. Therefore, using the nonlinear analysis program that NASS (Nonlinear Analysis for Spatial Structures) perform nonlinear analysis, and stress distribution for creak length investigate for using linear elastic fracture mechanics.

  • PDF

Effect of Initial Shape Imperfection and Residual Stress on the Ultimate Strength of Ring-Stiffened Cylinders under Hydrostatic Pressure (수압을 받는 원환보강원통의 최종강도에 대한 초기 형상결함과 잔류응력의 영향)

  • 조상래;김승민
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
    • /
    • /
    • pp.139-143
    • /
    • 2001
  • Ring-stiffened cylinders are widely used as the pressure hull of submarines and underwater vehicles. For large ring-stiffened cylinders cylindrical shells are fbricated by cold rolling of flat plates and then welding of curved shells. After forming cylinders ring-stiffeners are welded on th the cylinders. Due to these cold roiling and welding initial shape imperfections and residual stresses exists in fabricated ring-stiffened cylinders. It is well known that the initial shape and material imperfections affect the ultimate strength of ring-stiffened cylinders significantly. In this paper previous researches on the effects of initial shape imperfections and residual stresses are briefly reviewed Recently a numerical analysis computer program was developed to predict the ultimate strength of ring-stiffened cylinders subjected to hydrostatic pressure, which is based on the Dynamic Relaxation technique. This program was employed to numerically investigate those effects. The numerical predictions were substantiated with relevant experimental results.

  • PDF

A Study on the Intial Blank Design Using Ideal Forming Theory (이상적 변형이론을 이용한 박판 초기형상 설계에 관한 연구)

  • 박상후;윤정환;양동열;김용환;이장희
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.5 no.4
    • /
    • pp.207-218
    • /
    • 1997
  • A new blank design method is introduced to predict the blank shape and the strain distribution in the sheet metal forming process. This method deals with only one step from the final shape to the initial blank using the ideal forming theory. Based on this theory, a three-dimensional membrane finite element code has been developed to design an initial blank in the sheet metal forming process. In this paper, the designs of initial blanks for forming a cylindrical cup, a rectangular cup, and a front fender are presented as examples. Also, it compares the two shapes, the target shape with the shape which is deformed from the initial blank using the FEM analysis code. The results illustrate the information that this direct design code is useful in the preliminary design state.

  • PDF

A Study on the T-branch Forming with 3-D Finite Element Method (3차원 유한요소법을 이용한 T형 가지관의 용접자리 성형 방법에 관한 연구)

  • 홍대훈;황두순;신동필;홍성인
    • Transactions of Materials Processing
    • /
    • v.10 no.1
    • /
    • pp.23-29
    • /
    • 2001
  • In this study, the optimized initial hole shape for T-branch forming was proposed to obtain effective welding region. Design variables were determined by approximation analysis using volume constant condition. We performed 3D elastic-plastic FEM(Finite Element Method) analysis to simulate T-branch forming process. The variation of height and thickness of T-branch with various hole shapes was investigated. The optimized initial hole shape equation was obtained by using results for the numerical analysis.

  • PDF

Vibration Mode Shape Changed by Phase Angle in Vibration Testing Using Phase-Shifting ESPI (위상이동 ESPI를 이용한 진동실험에서 위상각에 따른 진동모드 형상의 변화)

  • 정현철;김경석;양승필;장호섭;박찬주;조영학;김종수
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.443-446
    • /
    • 2003
  • The vibration mode shape changed by the phase angle that can be controlled by phase-shifting ESPI system is discussed. For the phase-shifting ESPI experiment the stroboscopic illumination by using AOM(Acousto-Optic Modulator) is needed, and the initial phase angle can be adjusted by the program. The vibration mode shape is changed when the initial phase angle is changed. We examined the vibration mode shape change due to the initial phase angle change at each resonance frequency. Through this study, we found that in the vibration testing using phase-shilling ESPI the vibration mode shape is improved in the quality by adjusting exact phase angle and the error of the quantitative vibration analysis can be reduced.

  • PDF

A Simplified Analysis Method for Determining an Optimized Initial Shape of Cable-Stayed Bridges (사장교의 최적 초기형상 및 무응력길이 결정을 위한 간략해석법)

  • Jung, Myung Rag;Park, Se Woong;Min, Dong Ju;Kim, Moon Young
    • Journal of The Korean Society of Civil Engineers
    • /
    • v.36 no.6
    • /
    • pp.947-954
    • /
    • 2016
  • A simplified analysis method is first proposed in order to determine an optimized initial shape of cable-stayed bridges including all unstrained element lengths without using complicated nonlinear FE analysis. The unstrained-length based FE method is then presented using the unstrained lengths by the simplified analysis. To demonstrate validity and accuracy of the proposed method, Incheon bridge model having the fabrication camber is constructed and initial shaping analysis is performed using the presented method and commercial finite element analysis program, MIDAS. Resultantly it is shown that the initial solutions by the proposed algorithm are well optimized and in good agreement with those by MIDAS except for axial displacements of the main member.

Optimum Blank Design of Automobile Sub-Frame (우물정자형 Sub-frame의 블랭크 설계)

  • 김종엽;김낙수;허만성
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • /
    • pp.185-195
    • /
    • 1998
  • 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 final deformed shape and target contour shape into account. Based on the method, a computer program composed of blank design module, FE-analysis program and mesh generation module is developed. The rollback method is applied to square cup drawing process with the flange of unifiorm size around its periphery to confirm its validity. The optimum initial blank shape is obtained from an arbitrary square blank after three modifications. Good agreements are recognized between the numerical results and the published results for initial blank shape and thickness strain distribution. The optimum blank shape for two parts of automobile sub-frame is designed. The thickness distribution and the level of punch load is improved. Also, the method is applied to design the weld line in the tailor-welded blank. It is concluded that the rollback method is an effective and convenient method for an optimum blank shape design.

  • PDF

Level Set Based Shape Optimization of Linear Structures Using Topological Derivatives (Topological Derivative를 이용한 선형 구조물의 레벨셋 기반 형상 최적 설계)

  • Ha Seung-Hyun;Kim Min-Geun;Cho Seon-Ho
    • Proceedings of the Computational Structural Engineering Institute Conference
    • /
    • /
    • pp.299-306
    • /
    • 2006
  • Using a level set method and topological derivatives, a topological shape optimization method that is independent of an initial design is developed for linearly elastic structures. In the level set method, the initial domain is kept fixed and its boundary is represented by an implicit moving boundary embedded in the level set function, which facilitates to handle complicated topological shape changes. The 'Hamilton-Jacobi (H-J)' equation and computationally robust numerical technique of 'up-wind scheme' lead the initial implicit boundary to an optimal one according to the normal velocity field while minimizing the objective function of compliance and satisfying the constraint of allowable volume. Based on the asymptotic regularization concept, the topological derivative is considered as the limit of shape derivative as the radius of hole approaches to zero. The required velocity field to update the H -J equation is determined from the descent direction of Lagrangian derived from optimality conditions. It turns out that the initial holes is not required to get the optimal result since the developed method can create holes whenever and wherever necessary using indicators obtained from the topological derivatives. It is demonstrated that the proper choice of control parameters for nucleation is crucial for efficient optimization process.

  • PDF

Numerical Study on Sheet Metal Forming Analysis Using the One-Step Forming (One-Step Forming을 이용한 박판성형 해석에 관한 연구)

  • Ahn H. G.;Ko H. H.;Lee C. H.;Ahn B. I.;Moon W. S.;Jung D. W.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • /
    • pp.419-422
    • /
    • 2005
  • Many process parameters have an effect on the auto-body panel forming process. A well-designed blank shape causes the material to flow smoothly, reduces the punch and yields a product with uniform thickness distribution. Therefore, the determination of an initial blank shape plays the important role of saving time and cost in the auto-body panel forming process. For these reasons, some approaches to estimate the initial blank shape have been implemented in this paper, the one-step approach by using a finite element inverse method will be introduced to predict the initial blank shape the developed program is applied to auto-body panel forming.

  • PDF