• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.183-195
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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 nitration control for the beam structures with bonded plate-tyPe Piezoelectric sensors and actuators is proposed.

• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.509-518
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• 2002

In order to perform the spatial buckling and static analysis of the nonsymmetric thin-walled beam-column element, improved exact static stiffness matrices were evaluated using equilibrium equation and force-deformation relationships. This numerical technique was obtained using a generalized linear eigenvalue problem, by introducing 14 displacement parameters and system of linear algebraic equations with complex matrices. Unlike the evaluation of dynamic stiffness matrices, some zero eigenvalues were included. Thus, displacement parameters related to these zero eigenvalues were assumed as polynomials, with their exact distributions determined using the identity condition. The exact displacement functions corresponding to three loadingcases for initial stress-resultants were then derived, by consistently combining zero and nonzero eigenvalues and corresponding eigenvectors. Finally, exact static stiffness matrices were determined by applying member force-displacement relationships to these displacement functions. The buckling loads and displacement of thin-walled beam were evaluated and compared with analytic solutions and results using ABAQUS' shell element or straight beam element.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.614-621
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• 2019

A generalized laminated composite beam element is presented for the flexural and buckling analysis of laminated composite beams with double and single symmetric cross-sections. Based on shear-deformable beam theory, the present beam model accounts for transverse shear and warping deformations, as well as all coupling terms caused by material anisotropy. The plane stress and plane strain assumptions were used along with the cross-sectional stiffness coefficients obtained from the analytical technique for different cross-sections. Two types of one-dimensional beam elements with seven degrees-of-freedom per node, including warping deformation, i.e., three-node and four-node elements, are proposed to predict the flexural behavior of symmetric or anti-symmetric laminated beams. To alleviate the shear-locking problem, a reduced integration scheme was employed in this study. The buckling load of laminated composite beams under axial compression was then calculated using the derived geometric block stiffness. To demonstrate the accuracy and efficiency of the proposed beam elements, the results based on three-node beam element were compared with those of other researchers and ABAQUS finite elements. The effects of coupling and shear deformation, support conditions, load forms, span-to-height ratio, lamination architecture on the flexural response, and buckling load of composite beams were investigated. The convergence of two different beam elements was also performed.

• Journal of KSNVE
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• v.8 no.1
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• pp.157-170
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• 1998

This paper proposes a new technique to formulate the finite element model of a sandwich beam by using GHM (Golla-Hughes-McTavish) internal auxiliary coordinates to account for frequency dependence. Through the use of auxiliary coordinates, the equation of motion of undamped mass and stiffness matrix form is extended to encompass viscoelastic damping matrix. However, this methods all suffer from an increase in order of the final finite element model which is undesirable in many applications. Here we propose to combine the GHM method with model reduction techniques to remove the objection of increased model order.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.600-606
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• 2006

실제 지반은 경계가 없는 무한상태로 존재하기 때문에 지반구조물의 동적거동을 유한요소법을 이용하여 해석할 시 모델의 영역을 성립하는 것은 특별한 고려가 필요하다. 유한요소법에서의 동적해석은 파동의 전달을 포함하기 때문에 모델의 경계에서 인공적인 경계조건이 필요하다. 인공적인 경계 조건은 유한요소내의 지반상태를 무한상태로 변형시킬 수 있어야 하며, 경계에 도달하는 응력 파동을 모델내로 반사시키지 않고 흡수 할 수 있어야 한다. 본 논문에서는 간단한 점 탄성 반무한 불연속 요소를 이용하여 지반구조물의 동적해석을 수행하는 방법을 보여준다. 반무한 요소의 실행은 OpenSees라는 유한요소 해석프로그램을 이용하여 수행되었으며, 예를 통하여 불연속 요소가 경계에 도달하는 응력 파동을 충분히 흡수하여 유한요소 모델을 반무한 상태로 전환 시킬 수 있다는 것을 보여준다.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.833-846
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• 2004

This study presents a non-prismatic beam element for modeling the elastic behavior of steel beams, which have the post-Northridge connections in steel moment frames. The elastic stiffness matrix, including the shear effects for non-prismatic members with reduced beam section (RBS) connection, is in closed form. A simplified approach is also suggested, which uses a prismatic beam element to model beams with the RBS connection. This method can estimate quiteexactly the maximum story drift ratios of frames with the RBS connection. The effects of reduced beam section connection on the elastic stiffness of steel moment frames were investigated. The selection of a proper model to account for deformations at the joint might have a more important role in estimating the maximum story drift ratios of frames with better accuracy than the RBS cutouts.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.27-35
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• 2007

This study presents a non -prismatic beam element for modeling the elastic and inelastic behavior of the steel beam, which has the post-Northridge connections in steel moment frames that are subjected to earthquake ground motions. The elastic stiffness matrix for non-prismatic members with reduced beam section (RES) connection is in the closed-form. The plasticity model is of a discrete type and is composed of a series of nonlinear hinges connected by rigid links. The hardening rules can model the inelastic behavior for monotonic and random cyclic loading, and the effects of local buckling. Verification and calibration of the model are presented in a companion paper.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.523-532
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• 2006

It is thought that the suggestion of efficient and rational design guideline based on the behavior evaluation of bridge structure system the included cross beam is necessary for the construction efficiency of two-I girder steel bridges. Therefore, in this study, the effects of influence parameters are investigated by the behavior analyses of the bridges, in which the influence parameters are location, spacing and rigidity of the cross beam. For this study, the existed two-I girder steel bridges firstly were selected with the model of case study and the FE analyses for some case models were performed to estimate the action of the cross beam in the bridge. From the analyses, it was estimated that if it consider local stress and load distribution of a floor system, shell and solid elements are compatible to modeling of the cross beams. Also, the efficient design guideline for the cross beam of two-I girder steel bridge was suggested from parameter studies used location, spacing and rigidity of the cross beam.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.233-238
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• 1995

주파수 응답함수를 직접 이용하는 응답함수 방법을 이용하여 8자유도계, 보, 그리고 보구조물의 모의실험과 실험을 통해 다음과 같은 결론을 얻었다. 첫째, 잡음이 혼입된 경우도 데이타를 취하는 주파수 점의 개수를 늘려줌으로써 정확한 결과를 얻는 것이 가능하다. 둘째, 실제 보에 대해서 유한요소모델의 개선을 행하여 실험과 일치하는 결과를 얻을 수 있다. 세째, 볼트로 체결된 보구조물에 대해 유한요소모델의 개선을 통한 결합부의 동정을 통해 실험과 더 잘 일치하는 유한요소모델을 얻을 수 있다.

• Journal of Ocean Engineering and Technology
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• v.13 no.1 s.31
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• pp.39-50
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• 1999

특이 가중함수로 표현된 shepard interpolant와 일관조건을 사용하여 무요소법 형성함수를 도출하였다. 따라서 통상의 EFGM(Element Free Galerkin Method)과는 달리 변위로 주어지는 경계조건을 자연스럽게 부과할 수 있다. 수치계산 예로서 외팔보 문제를 다루었는데 보이론과 비교하여 매우 잘 맞는 결과를 보여주고, 유한요소법과의 결합도 자연스럽게 이루어짐을 보인다. 또 penny-shaped 균열을 다루는데, 응력확대계수는 균열 표면의 변위로부처 직접 계산하여 해석해와 비교한다.