• Structural Engineering and Mechanics
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• 제22권4호
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• pp.483-510
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• 2006

The dynamic instability characteristics of laminated composite stiffened shell panels subjected to in-plane harmonic edge loading are investigated in this paper. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the shell panels and the stiffeners respectively. As the usual formulation of degenerated beam element is found to overestimate the torsional rigidity, an attempt has been made to reformulate it in an efficient manner. Moreover the new formulation for the beam element requires five degrees of freedom per node as that of shell element. The method of Hill's infinite determinant is applied to analyze the dynamic instability regions. Numerical results are presented to demonstrate the effects of various parameters like shell geometry, lamination scheme, stiffening scheme, static and dynamic load factors and boundary conditions, on the dynamic instability behaviour of laminated composite stiffened panels subjected to in-plane harmonic loads along the boundaries. The results of free vibration and buckling of the laminated composite stiffened curved panels are also presented.

• Steel and Composite Structures
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• 제17권6호
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• pp.867-890
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• 2014

This paper deals with the geometric nonlinear bending analysis of laminated composite stiffened plates subjected to uniform transverse loading. The eight-noded degenerated shell element and three-noded degenerated curved beam element with five degrees of freedom per node are adopted in the present analysis to model the plate and stiffeners respectively. The Green-Lagrange strain displacement relationship is adopted and the total Lagrangian approach is taken in the formulation. The convergence study of the present formulation is carried out first and the results are compared with the results published in the literature. The stiffener element is reformulated taking the torsional rigidity in an efficient manner. The effects of lamination angle, depth of stiffener and number of layers, on the bending response of the composite stiffened plates are considered and the results are discussed.

• Selected Papers of The Society of Naval Architects of Korea
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• 제1권1호
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• pp.91-100
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• 1993

A displacement-based finite element method Is presented for the geometrically nonlinear analysis of eccentrically stiffened plates. A nonlinear degenerated shell element and a nonlinear degenerated eccentric isoparametric beam (isobeam) element are formulated on the basis of Total Agrangian and Updated Lagrangian descriptions. In the formulation of the isobeam element, some additional local decrees of freedom are implementd to describe the stiffener's local plate buckling modes. Therefore this element can be effectively employed to model the eccentric stiffener with fewer D.O.F's than the case of a degenerated shell element. Some detailed buckling and nonlinear analyses of an eccentrically stiffened plate are performed to estimate the critical buckling loads and the post buckling behaviors including the local plate buckling of the stiffeners discretized with the degenerated shell elements and the isobeam elements. The critical buckling loads are found to be higher than the analytical plate buckling load but lower than Euler buckling load of the corresponding column, i.e, buckling strength requirements of the Classification Societies for the stiffened plates.

• Structural Engineering and Mechanics
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• 제35권3호
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• pp.315-333
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• 2010

The structural behaviors of circular concrete filled steel tube (CFT) structures are investigated by nonlinear finite element method. An efficient three-dimensional (3D) degenerated beam element is adopted. Based on those previous studies, a modified stress-strain relationship for confined concrete which introduces the influence of eccentricity on confining stress is presented. Updated Lagrange formulation is used to consider the geometrical nonlinearity induced by large deformation effect. The nonlinear behaviors of CFT structures are investigated, and the accuracy of the proposed constitutive model for confined concrete is mainly concerned. The results demonstrate that the confining effect in CFT elements subjected to combining action of axial force and bending moment is far sophisticated than that in axial loaded columns, and an appropriate evaluation about this effect may be important for nonlinear numerical simulation of CFT structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.398-405
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• 1997

The finite element program is presented for the analysis of the moment distribution in continuous slabs of simply supported girders. The program includes the material nonlinearity of the continuous and steel reinforcements of the RC slabs, but assumes that the PC beam and cross beam behave linearly. In modeling the PC slabs and girders, the four node degenerated shell element formulated based on the assumed strain interpolation and the 3D beam element are used, respectively. Using the program, the influence of the existence of the cross bean, the filling of open joints on the continuous at supports, and perfect continuation of precast girder elements are examined.

• 대한기계학회논문집
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• 제19권2호
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• pp.354-362
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• 1995

The finite element modeling is used to study the buckling and postbuckling behavior of composite laminates with an embedded delamination. Degenerated shell element and rigid beam element are utilized for the finite element modeling. In the nonlinear finite element formulation, the updated Lagrangian description method based on the second Piola-Kirchhoff stress tensor and the Green strain tensor is used. The buckling and postbuckling behavior of composite laminates with a delamination are investigated for various delamination sizes, stacking sequences, and boundary conditions. It is shown that the buckling load and postbuckling behavior of composite laminates depend on the buckling model which is determined by the delamination size, stacking sequence and boundary condition. Also, results show that introduction of couplings can reduce greatly the buckling load.

• 대한토목학회논문집
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• 제4권3호
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• pp.53-61
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• 1984

본(本) 연구(硏究)에서는 2차원(次元) 탄성(彈性) 뼈대 구조물(構造物)의 기하학적(幾何學的) 비선형(非線型) 해석(解析)을 위하여 Total Lagrangian 방법(方法)에 의한 보 유한요소(有限要素)(NB6)의 Formulation을 보여주고 있다. 이 보 요소(要素)는 3 차원(次元) 연속체(連續體)로부터 깊은 보 가정(假定) 이용(利用)하여 유도(誘導)되며 3개(個)의 기준절점(基準節點)과 3개(個)의 상대절점(相對節點)으로 이루어진다. 보의 운동방정식(運動方程式)은 Galerkin의 가중잔차법(加重殘差法)으로 Discretization 되며 요소강도(要素剛度) 및 질량(質量)매트릭스는 Newton-Raphson 방법(方法)으로 해하중(每荷重) 단계(段階)마다 반복계산(反復計算)되어 감소적분법(減少積分法)으로 구해진다. 본(本) 연구(硏究)에서 제안(提案)되는 NB6 비선형(非線形) 보 요소(要素) 정확도(正確度)와 효율성(效率性) 고찰(考察)하기 위하여 몇 가지 예제(例題) 해석(解析)하였다.

• Structural Engineering and Mechanics
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• 제14권3호
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• pp.245-262
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• 2002

The free vibration analysis of stiffened laminated composite plates has been performed using the layered (zigzag) finite element method based on the first order shear deformation theory. The layers of the laminated plate is modeled using nine-node isoparametric degenerated flat shell element. The stiffeners are modeled as three-node isoparametric beam elements based on Timoshenko beam theory. Bilinear in-plane displacement constraints are used to maintain the inter-layer continuity. A special lumping technique is used in deriving the lumped mass matrices. The natural frequencies are extracted using the subspace iteration method. Numerical results are presented for unstiffened laminated plates, stiffened isotropic plates, stiffened symmetric angle-ply laminates, stiffened skew-symmetric angle-ply laminates and stiffened skew-symmetric cross-ply laminates. The effects of fiber orientations (ply angles), number of layers, stiffener depths and degrees of orthotropy are examined.

• 대한토목학회논문집
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• 제3권4호
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• pp.109-122
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• 1983

본(本) 연구(硏究)에서는 전단변형(剪斷變形)(Shear deformation)과 회전관성(回轉慣性)(Rotatory inertia)의 영향(影響)을 고려(考慮)한 4절점(節點) 8자유도(自由度)를 갖는 Timoshenko 보 요소(要素)(TB4)를 3차원(次元) 연속체(連續體)로부터 유도(誘導)하고 있다. TB4보 요소(要素)는 3차(次) 보간함수(補間凾數)(Interpolation function)로 표시(表示)되는 연직(鉛直)처짐(Transverse deflection) W와 평면회전(平面回轉)(Plane rotation) ${\theta}$를 절점(節點)의 자유도(自由度)로 취(取)하고 있다. TB4요소(要素)의 강도(剛度)매트릭스와 질량(質量)매트릭스는 보의 운동방정식(運動方程式)을 Galerkin 가중잔차법(加重殘差法)(Weighted residual method)으로 Discretization하여 3개(個)의 Gauss점(點)을 이용(利用)한 RSI(Reduced shear integration)기법(技法)에 의한 수치적분(數値積分)으로 구해진다. TB4보 요소(要素)의 정확성(正確性)과 수감상태(收歛狀態)를 고찰(考察)하기 위하여 여러 가지 예제(例題)를 해석(解析)한 결과(結果), 보의 L/h 비(比)에 관계없이 보의 정적해석(靜的解析)(Static analysis)이라 자유진동해석(自由振動解析)(Free vibration analysis)에 있어서 TB4보 요소(要素)는 다른 Timoshenko보 요소(要素)들 보다 월등(越等)히 우수(優秀)한 정확도(正確度)와 수감현상(收歛現象)을 보여 주고 있다.

• 대한조선학회논문집
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• 제29권4호
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• pp.227-233
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• 1992

3차원 편심 보요소의 기하학적 비선형 해석에서 증분 평형식을 유도하는 일반적인 방법의 대부분은 비선형을 고려한 가상일의 평형방정식을 선형화하는 방법으로, 회전증분이 미소하다는 가정에 의해서 선형화된 증분 평형식을 유도하고, 구조물의 변형이 일어나는 동안에 발생하는 유한회전의 영향은 반복계산의 과정에서 고려하는 방법이다. 그리고 유한회전을 고려하는 개선된 방법으로 Surana와 Onate 등에 의해서 개발되었는데, Surana는 비선형 절점함수를 가정하였고, Onate는 회전행렬의 관계식을 이차항까지 고려하여 비선형 증분 평형식을 유도하였다. 본 논문에서는 비선형 해석의 증분이론(incremental theory)을 도입, $^{t+dt}U_i$ 변위증분을 Talyer 급수로 2차항까지 전개하므로서 1차 선형항($U_L$)과 2차 유한회전항($U_R$)으로 표시하여 연속체운동의 비선형 증분평형식에서 유한회전의 영향을 고려하는 방법을 사용하였다. 이상의 해석방법에 따른 수치해석 결과는 Surana와 Onate등에 의하여 다루어진 예제와 비교 하였다.