보요소와 쉘요소를 결합시킨 變斷面 部材의 挫屈解析에 관한 硏究

김주원 부산대학교 대학원 1998 국내박사

This study permits the finite element method by using the transfer matrix combined the beam element and shell element. And the non-linear finite element analysis has been presented to investigate the ultimate load and deformation of nonprismatic members with openings and restraints. The stiffness matrix for a 14 degrees of freedom beam element of a general asymmetric thin-walled open-section is formulated. The governing equation for thin-walled elements is developed using complete expression for the strain, including the second order strain terms. The efficiency of a 4-node qurdrilateral shell element is shown for calculations involving non-linearities such as large rotations and large strains. The membrane part of the element has 12 degrees of freedom including rotational or 'drilling' degrees of freedom at the nodes. The bending part of element also has 12 degrees of freedom. This element uses the discrete Krichhoff technique. The element formulation is derived from an 8-node isoparametric element by expressing the midside displacement degrees of freedom in terms of displacement and rotational degrees of freedom at corner nodes. Through the discrete layered method, the elasto-plastic incremental constitutive relation is defined with von Mises yield criterion and associated flow rule in which the plastic potential is assumed to be the yield function. The transfer matrix combined beam element and shell element, is derived by using equilibrium equations. An approximate non-linear analysis has achieved by load incremental solution and tangential stiffness. In this research, the experimental investigations are carried out on the buckling behaviour of reinforced C-section members. From the comparison of existing numerical examples and experiment, it is concluded that : 1. The flexural-torsional buckling of reinforced C-section members is investigated, the mean error between experimental results and those of the suggested method exist 8.5%, thus the application of the suggested method is proved. 2. It is investigated that the structural behaviour of the buckling of columns with two end rotational springs and midspan translational spring. The mean error between this study and previous study exist. 3. The results on the ultimate loads of beam with opening by the suggested methods agree with those by previous study. 4. Suggested program can be analysed the inelastic buckling load of the cantilever with a opening and a rotational restraint, so this program can be applied to decision of the ultimate load of nonprismatic members due to the discontinuity of the axis.

平面三角 쉘要素를 利用한 積層 構造物의 幾何學的 非線型 解析

장명호 成均館大學校 大學院 2003 국내박사

Finite element analysis of thin laminated shells using a three-node flat triangular shell element is presented. The flat shell element is obtained by combining the Discrete Kirchhoff Theory (DKT) plate bending element and a membrane element derived from the Linear Strain Triangular (LST) element. The element is first thoroughly tested for linear static analysis of laminated plates and shells and geometrically nonlinear analysis. The geometrically nonlinear analysis is performed using an updated Lagrangian formulation employing Green strain and Second Piola-Kirchhoff (PK2) stress measures. A linear displacement field is used for transverse displacement in order to compute the derivatives of the transverse displacement that are required to compute the geometric stiffness or the initial stress matrix. The wind load is modeled as a non-uniform pressure load and the snow load as lumped concentrated load. Since the direction of the pressure load is assumed to be normal to the current configuration of the structure, it changes as the structure undergoes deformation. This is called the follower action.. As a result, the pressure load is a function of the displacements and hence contributes to the tangent stiffness matrix in the case of geometrically nonlinear analysis. This contribution (called the pressure stiffness) is in general unsymmetric and its determination is not straightforward, but can be systematically derived from the principle of virtual work. The follower effects of the pressure load have been included in the updated Lagrangian formulation of the flat shell element. Several numerical examples are solved to demonstrate the accuracy of the formulation for both small and large rotation analysis of laminated plate and shell. The results are compared with those available in the existing literature and those obtained using the commercial finite element package ABAQUS and are found to be in good agreement.

유한요소법을 이용한 지능구조용 압전 작동기 적용 구조물의 작동변위 해석 및 검증

이상기 건국대학교 대학원 2005 국내박사

한글초록:유한요소법을 이용하면 복잡한 형상과 경계조건을 갖는 압전 작동기 적용 지능구조물의 모델링 및 성능 예측을 용이하게 할 수 있어, 시행착오를 줄이며 보다 우수한 작동기 및 작동기 응용 구조물을 효과적으로 설계/제작하는 것이 가능하다. 이에 본 연구에서는 압전 작동기 적용 구조물의 작동변위 해석에 기여할 수 있는 압전 솔리드(piezo-solid) 및 압전 쉘(piezo-shell) 요소를 이용한 유한요소해석 프로그램들을 개발하였다. 개발된 프로그램들은 각종 수치예제 통해 검증하였으며, 이렇게 검증된 유한요소 프로그램들을 이용하여 압전 복합재 작동기 LIPCA의 작동변위 해석을 수행하고 측정결과와의 비교를 수행하였다. 특히 인가전압에 대한 LIPCA 작동기의 비선형 거동을 보다 정확히 모사하기 위하여 압전재의 재료 비선형 특성을 측정하였고, 측정 결과와 선형 압전 쉘 요소를 바탕으로 개발한 재료 비선형 프로그램을 이용하여 비선형 거동 해석을 수행하였다. 한편 상용 유한요소 프로그램을 이용한 열 등가 모델링 기법의 검증을 수행하였고, LIPCA를 적용한 지능구조물 해석에 활용하였다 영문초록:Currently, intensive efforts are devoted to develop high performance actuators. Piezoceramic, piezopolymer, electro-active polymer, shape memory alloy materials show promising properties for potential use as the non-conventional actuators. These actuators are expected to be applicable to various technical disciplines such as suppressing vibrations of marine or aerospace structures, actuating control surfaces of small-scale airplanes, morphing wing sections, and so on.Up to date, several successful piezoelectric actuators have been introduced such as THUNDER, RAINBOW, and LIPCA (LIghtweight Piezo-Composite Actuator). For development of high performance piezo-composite actuators including THUNDER, and LIPCA, estimation of actuator behavior is very important due to reduced effort and time required for the trial-and-error fabrication and test. The finite element method (FEM) can be used to predict piezo-composite actuators' behavior. The finite element method is a powerful tool because it can model complicated shapes and apply various boundary conditions. In this study, piezo-shell and piezo-solid finite element programs have been developed based on the coupled electro-mechanical formulations for analyses of piezoelectric actuator embedded structures

강합성 박스거더교의 전단지연분석

김민수 서울시립대학교 산업대학원 2009 국내석사

강합성 박스거더교의 단면은 얇은 강판으로 조합된 형태로 가벼운 자중과 휨 강성 및 비틀림 강성이 다른 교량 형식에 비하여 월등히 우수하여 장지간 교량 구조물에 많이 사용되고 있다. 강박스 거더와 콘크리트 바닥판의 합성구조는 콘크리트 바닥판이 상부플랜지의 역할을 하므로 복부에서 전달되는 전단력에 의해 불균등한 전단변형이 발생한다. 따라서 복부와 플랜지가 만나는 지점에 큰 응력이 발생하는 구조적 특성을 나타낸다. 실무 설계에서 전단지연 현상에 의해 발생되는 불균등한 응력분포를 고려하기 위해 최대 응력이 전단면에 균일하게 작용한다는 유효폭 개념을 적용하고 있다. 유효폭 개념에 의해 단면을 감소시켜 응력을 검토하는 경우 복부와 플랜지가 접하는 부분에서 국부적인 응력집중과 전단지연현상에 의해 발생되는 응력보다 과소 평가 될 수 있다. 그러므로 본 논문은 강합성 박스거더교의 전단지연에 의한 응력분포를 분석하기 위하여 보요소 및 쉘요소를 이용한 유한요소해석을 수행하였다. 해석 결과, 경간 지점부의 하부플랜지는 복부와 플랜지가 접하는 부분에서 가장 큰 압축응력이 나타나고 복부에서 멀어질수록 압축응력이 감소하는 경향을 나타내었다. 이러한 현상은 전단지연 효과에 의한 현상과 동일한 응력 분포를 나타내었으나 최대 응력은 보해석에 의한 응력보다 크게 발생하는 것으로 나타났다. 따라서 더욱 정확한 설계을 위해서는 유효폭 개념에 의한 응력 평가뿐만 아니라 상세해석에 의한 응력을 분석할 필요가 있는 것으로 판단된다. Steel-composite box girder bridge with thin steel plates is widely used in long span bridge because it has light self-weight, and is superior bending and torsion stiffness to any other type of bridges. In this structure composited by steel box girders and concrete base-plates, the concrete slab play a role as upper flange, and the unbalanced shear deformation is caused by transmitting shear force to the upper part. Therefore, the structure shows the structural characteristic which is large stress at the joint between web and flange. The concept of effective width that maximum stress acts on equivalently constant section is applied in the practical design to consider unbalanced distribution of stress due to the phenomenon of shear lag. The stress due to shear lag more underestimate than the stress due to local concentrated stress between web and flange when the applied sections are reduced by the concept of effective width. Consequently, this study performs the analysis of finite element involving beam and shell element in order to analyze the distribution of stress arising from steel-composite box girder because of shear lag. This study reaches the results that the largest compression stress is shown in the adjoined end support of bottom flange. Furthermore, the stresses have a tendency of reducing compression stress as far from web. This phenomenon shows the same as the distribution of stress with the effect of shear lag, but maximum stress is larger than beam analysis. Accordingly, the stress calculated by the effective width and stress by finite element method are required for more accurate design.

쉘요소 구조물과 유연이음 보요소 구조물의 등가방안

이창훈 연세대학교 1995 국내석사

直交異方性 쉘要素를 利用한 波形무늬 배럴의 解析에 關한 硏究

조근규 연세대학교 1987 국내석사

박판부재의 붕괴거동해석을 위한 극한해석의 쉘요소 수식화

김현섭 한국과학기술원 2000 국내박사

Development of 4-Node cylindrical shell element including curvature effect in displacement field

최진유 Korea Univ. 2000 국내박사

Improved shell finite elements for linear and nonlinear analysis of shell structures

Yoo, Seung-woon Korea Advanced Institute of Science and Technology 1990 국내박사

쉘 요소를 이용한 PSC교량의 시공중 해석

김영회 건국대학교 대학원 2008 국내석사

프리스트레스트 콘크리트 구조물은 시공중 단계와 완성계 단계에 대한 구조해석이 필요하다. 콘크리트 크리프, 수축, 탄성(강도)계수 그리고 텐던의 릴랙세이션 등과 같은 시간외존 특성이 다양하기 때문에 처짐과 응력 재분배와 같은 구조적 거동은 시공중 또는 시공후에도 계속적으로 변화한다. 다양한 하중과 지지조건 그리고 순서에 입각한 각 시공단계를 확인하는 것이 요구된다. 하지만 그런 단계 없는 해석은 신뢰도가 떨어진다. 본 연구의 목적은 PSC 구조물의 시간의존 거동을 연구하는 것이다. 프리스트레스트 콘크리트 구조물은 콘크리트, 보강 철근 그리고 PS 강재로 이루어지기 때문에, 구조물의 해석은 매우 복잡하게 된다. 이 논문은 수치예제를 통해 일반적으로 쓰이고 있는 ACI 코드와 CEB-FIP 코드에 의거한 결과를 비교하고, 프레임 요소 모델과 쉘 요소 모델을 사용해 그 결과를 서로 비교하였다. A prestressed concrete structure such as bridge or cable stayed bridge requires separate and yet inter-realted analyses for the completed structure and interim structures during the construction. The structural bahaviors such as deflections and stress re-distribution continue to change during and after the construction due to varying time defendant propeties such as concrete creep, shrinkage, modulus of elasticity(aging) and tendon realxation. Since the structural configuration continuously changes with different loading and support conditions, and each construction stage affects the subsequent stages, the design of certain structural components may be governed during the construction. Accordingly, the time dependent construction stage analysis si required to examine each stage of the construction, and without such analysis fir the final stage alone will not be reliable. The purpose of this study is to investugate time dependent behaviot of PSC structures using XFINAS structural analysis program. Since prestresed concrete structures are builded by assembling of concrete, reinforced steel and prestressing steel, those amke an analysis much more complicated. This study showed the necessary of construction stage analysis and compared with both results of ACI Code and CEB-FIP Code which is widely used. Both of shell and frame elements are used to perform the analysis. The results are compared with each other. The first of study shown a necessary of construction stage analysis by compare between linear static analysis and construction stage analysis. Material properties, support condition, lack of fitting, the differences between construction stage analysis and linear static analysis, are generated differ losses of prestress. As a result, both displacements are vastly different. And the construction stage analysis is more rational. Moment redistribution due to change in boundary conditions, creep effect and time changes in material strength has been verified using ACI Code and CEB-FIP Code fomulations. The result from ACI and CEB-FIP code are different in compared of the response from construction stage analysis. The response of the structures modeled by frame and shell are different because in the shell model, the distortion of the structural section can be occurred but not in the frame model.