• 대한토목학회논문집
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• 제13권2호
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• pp.41-49
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• 1993

2차원 곡선보요소를 이용하여 대변형효과 및 탄소성거동을 고려한 유한요소법을 제시한다. Total Lagrangian 방법을 적용하며, 보요소는 평면응력요소로부터 유도된다. 또한, 임의의 단면을 갖는 평면뼈대 구조의 탄소성 해석을 수행하기 위하여 layered approach를 사용한다. 비선형 유한요소해석은 하중증분 또는 변위증분법을 적용한다. 본 연구에서 제안한 보요소의 거동과 정확도를 검증하기 위하여, 다른 문헌의 결과와 본 연구의 결과를 비교 분석한 해석예제를 제시한다.

• 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.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2000년도 가을 학술발표회논문집
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• pp.3-10
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• 2000

In this study, a new smart beam finite element is proposed for the finite element modeling of the beam-type smart structure with bonded plate-type piezoelectric sensors and actuators. Constitutive equations far the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered. By using the variational principle, the equations of motion for the smart beam finite element are derived. The presented 2-node beam finite element is isoparametric element based on Timoshenko beam theory. The validity of the proposed beam element is shown through comparing the analysis results of the verification examples with those of other previous researches. Therefore, by analyzing smart structures with smart beam finite elements, it is possible to simulate the control of the structural behavior by piezoelectric actuators with applied voltages and the monitoring of the structure behavior by piezoelectric sensors with sensed voltages.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.269-278
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• 2003

In this study, the method of the finite element modeling for free vibration control of beam-type smart structures with bonded plate-type piezoelectric sensors and actuators is proposed. Constitutive equations for the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered. By using the variational principle, the equations of motion for the smart beam finite element are derived, The proposed 2-node beam finite element is an isoparametric element based on Timoshenko beam theory. Therefore, by analyzing beam-type smart structures with smart beam finite elements, it is possible to simulate the control of the structural behavior by applying voltages to piezoelectric actuators and monitoring of the structural behavior by sensing voltages of piezoelectric sensors. By using the smart beam finite element and constant-gain feed back control scheme, the formulation of the free vibration control for the beam structures with bonded plate-type piezoelectric sensors and actuators is proposed.

• Journal of Mechanical Science and Technology
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• 제15권11호
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• pp.1499-1506
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• 2001

Various transition elements are used in general for the effective finite element analysis of complicated mechanical structures. In this paper, a solid-to-beam transition finite element, which can b e used for connecting a C1-continuity beam element to a continuum solid element, is proposed. The shape functions of the transition finite element are derived to meet the compatibility condition, and a transition element equation is formulated by the conventional finite element procedure. In order to show the effectiveness and convergence characteristics of the proposed transition element, numerical tests are performed for various examples. As a result of this study, following conclusions are obtained. (1) The proposed transition element, which meets the compatibility of the primary variables, exhibits excellent accuracy. (2) In case of using the proposed transition element, the number of nodes in the finite element model may be considerably reduced and the model construction becomes more convenient. (3) This formulation method can be applied to the usage of higher order elements.

• Structural Engineering and Mechanics
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• 제29권2호
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• pp.203-221
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• 2008

In this paper, we present an idea of the geometry-dependent MITC method. The simple concept is exemplified to improve a 2-node iso-beam (isoparametric beam) finite element of varying section. We first study the behavior of a standard 2-node iso-beam finite element of prismatic section, which has been widely used with reduced integration (or the equivalent MITC method) in order to avoid shear locking. Based on analytical studies on cantilever beams of varying section, we propose the axial strain correction (ASC) scheme and the geometry-dependent tying (GDT) scheme for the 2-node iso-beam element. We numerically analyze varying section beam problems and present the improved performance by using both ASC and GDT schemes.

• Structural Engineering and Mechanics
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• 제19권5호
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• pp.477-501
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• 2005

In this study, a new smart beam finite element is proposed for the finite element modeling of beam-type smart structures that are equipped with bonded plate-type piezoelectric sensors and actuators. Constitutive equations for the direct piezoelectric effect and converse piezoelectric effect of piezoelectric materials are considered in the formulation. By using a variational principle, the equations of motion for the smart beam finite element are derived. The proposed 2-node beam finite element is an isoparametric element based on Timoshenko beam theory. The proposed smart beam finite element is applied to the free vibration control adopting a constant gain feedback scheme. The electrical force vector, which is obtained in deriving an equation of motion, is the control force equivalent to that in existing literature. Validity of the proposed element is shown through comparing the analytical results of the verification examples with those of other previous researchers. With the use of smart beam finite elements, simulation of free vibration control is demonstrated by sensing the voltage of the piezoelectric sensors and by applying the voltages to the piezoelectric actuators.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.351-356
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• 2000

Various transition elements are generally used for the effective analysis of a complicated mechanical structure. In this paper, a solid-to-beam transition finite element which connects a continuum element and a $c^1-continuity$ beam element each other is proposed. The shape functions of the transition finite elements, which a 8-noded hexahedral solid element fur 3D analysis and a 4-noded quadrilateral plane element fur 2D analysis are connected to a Euler's beam element, are explicitely formulated. In order to show the effectiveness and convergence characteristics of the proposed transition elements. numerical tests are performed for various examples and their results are compared with those obtained by other methods. As the result of this study. following conclusions are obtained: (1)The proposed transition finite elements show the monotonic convergence characteristics because of having used the compatible displacement folds. (2)As being used the transition element in the finite element analysis, the finite element modelings are more convenient and the analysis results are more accurate because of the formulation characteristies of the Euler's beam element.

• Structural Engineering and Mechanics
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• 제19권1호
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• pp.73-96
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• 2005

For the spatially coupled free vibration analysis of shear deformable thin-walled non-symmetric curved beam subjected to initial axial force, an exact dynamic element stiffness matrix of curved beam is evaluated. Firstly equations of motion and force-deformation relations are rigorously derived from the total potential energy for a curved beam element. Next a system of linear algebraic equations are constructed by introducing 14 displacement parameters and transforming the second order simultaneous differential equations into the first order simultaneous differential equations. And then explicit expressions for displacement parameters are numerically evaluated via eigensolutions and the exact $14{\times}14$ dynamic element stiffness matrix is determined using force-deformation relations. To demonstrate the accuracy and the reliability of this study, the spatially coupled natural frequencies of shear deformable thin-walled non-symmetric curved beams subjected to initial axial forces are evaluated and compared with analytical and FE solutions using isoparametric and Hermitian curved beam elements and results by ABAQUS's shell elements.

• Steel and Composite Structures
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• 제15권2호
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• pp.175-202
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• 2013

The super convergent laminated composite beam element is newly derived for the lateral stability analysis. For this, a theoretical model of the laminated composite beams is developed based on the first-order shear deformation beam theory. The present laminated beam takes into account the transverse shear and the restrained warping induced shear deformation. The second-order coupling torque resulting from the geometric nonlinearity is rigorously derived. From the principle of minimum total potential energy, the stability equations and force-displacement relationships are derived and the explicit expressions for the displacement parameters are presented by applying the power series expansions of displacement components to simultaneous ordinary differential equations. Finally, the member stiffness matrix is determined using the force-displacement relationships. In order to show accuracy and superiority of the beam element developed by this study, the critical lateral buckling moments for bisymmetric and monosymmetric I-beams are presented and compared with other results available in the literature, the isoparametric beam elements, and shell elements from ABAQUS.