• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 가을 학술발표회 논문집
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• pp.239-246
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• 1996

Very stiff floor system in a residential-commercial building causes some problems in the numerical analysis procedure due to significant difference in stiffness with adjacent structural elements. Static analysis of structure with a stiff transfer-floor can be peformed approximately in two steps for upper and lower pons for the structure. However, it is impossible to perform dynamic analysis in two steps with separate models. An efficient method for dynamic analysis of a structure with a rigid floor system is proposed in this study. The matrix condensation technique is employed to reduce the degree of freedom for upper and lower parts of the structure and a beam elements with rigid bodies of both ends are introduce to model the rigid floor system. Efficiency end accuracy of the proposed method ore verified through analysis of several example structures.

• 대한기계학회논문집A
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• 제24권12호
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• pp.3003-3009
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• 2000

In this paper, we propose a new efficient hybrid-mixed C(sup)0 curved beam element with the optimal interpolation functions determined from numerical tests, which gives very accurate locking-free two-node curved beam element. In the element level, the stress parameters are eliminated from the stationary condition and the nodeless degrees of freedom are also removed by static condensation so that a standard six-by-six stiffness matrix is finally obtained. The numeri cal benchmark problems show that the element with cubic displacement functions and quadratic stress functions is the most efficient.

• 동력기계공학회지
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• 제15권6호
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• pp.47-52
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• 2011

In this study, an accurate 2-noded hybrid-mixed element for continuous fiber-reinforced laminated beams is newly proposed. The present element including the effect of shear deformation is based on Hellinger-Reissner variational principle, and introduces additional consistent node less degrees for displacement field interpolation in order to enhance the numerical performance. The micromechanical and lamination theory are employed in the finite element description to consider the effects of the laminate stacking sequences, material orthotropy, and fiber volume fraction, etc. The element stiffness matrix can be explicitly derived through the stationary condition and static condensation using Mathematica program. Several numerical examples confirm the accuracy of the present hybrid-mixed element and also show in detail the effects of the continuous fiber volume fraction, stacking sequences and boundary condition on the bending behavior of laminated beams.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.385-398
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• 2018

In the present paper, we offer a new flat shell finite element. It is the result of the combination of a membrane element and a bending element, both based on the strain-based formulation. It is known that $C^{\circ}$ plane membrane elements provide poor deflection and stress for problems where bending is dominant. In addition, they encounter continuity and compliance problems when they connect to C1 class plate elements. The reach of the present work is to surmount these problems when a membrane element is coupled with a thin plate element in order to construct a shell element. The membrane element used is a triangular element with four nodes, three nodes at the vertices of the triangle and the fourth one at its barycenter. Each node has three degrees of freedom, two translations and one rotation around the normal. The coefficients related to the degrees of freedom at the internal node are subsequently removed from the element stiffness matrix by using the static condensation technique. The interpolation functions of strain, displacements and stresses fields are developed from equilibrium conditions. The plate element used for the construction of the present shell element is a triangular four-node thin plate element based on Kirchhoff plate theory, the strain approach, the four fictitious node, the static condensation and the analytic integration. The shell element result of this combination is robust, competitive and efficient.

• 한국전산유체공학회지
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• 제10권2호
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• pp.38-47
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• 2005

Substructuring methods are often used in finite element structural analyses. In this study a multi-level substructuring(MLSS) algorithm is developed and proposed as a possible candidate for finite element fluid solvers. The present algorithm consists of four stages such as a gathering, a condensing, a solving and a scattering stage. At each level, a predetermined number of elements are gathered and condensed to form an element of higher level. At the highest level, each sub-domain consists of only one super-element. Thus, the inversion process of a stiffness matrix associated with internal degrees of freedom of each sub-domain has been replaced by a sequential static condensation of gathered element matrices. The global algebraic system arising from the assembly of each sub-domain matrices is solved using a well-known iterative solver such as the conjugare gradient(CG) or the conjugate gradient squared(CGS) method. A time comparison with CG has been performed on a 2-D Poisson problem. With one domain the computing time by MLSS is comparable with that by CG up to about 260,000 d.o.f. For 263,169 d.o.f using 8 x 8 sub-domains, the time by MLSS is reduced to a value less than $30\%$ of that by CG. The lid-driven cavity problem has been solved for Re = 3200 using the element interpolation degree(Deg.) up to cubic. in this case, preconditioning techniques usually accompanied by iterative solvers are not needed. Finite element formulation for the incompressible flow has been stabilized by a modified residual procedure proposed by Ilinca et al.[9].

• 한국공간구조학회논문집
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• 제11권3호
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• pp.95-103
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• 2011

비정형 초고층건물을 위한 구조시스템 중에서 다이어그리드 구조시스템은 구조적인 효율성 및 조형성 때문에 널리 사용되고 있다. 근래에는 초고층건물을 위한 구조시스템으로 메가부재의 조합을 통하여 횡방향 강성을 효과적으로 발휘할 수 있는 메가프레임 시스템이 널리 사용되고 있다. 두 가지 구조시스템의 장점을 혼합한 다이어그리드 메가프레임 구조시스템은 미래형 초고층건물에 적용될 유망한 구조시스템으로 평가받고 있다. 그러나 이러한 다이어그리드 메가프레임 구조시스템을 적용한 건물의 거동을 예측하기 위해서는 매우 많은 수의 절점과 요소로 이루어진 유한요소 모델을 해석해야 하므로 상당한 양의 해석시간과 엔지니어의 노력이 필요하게 된다. 따라서 본 연구에서는 다이어그리드 메가프레임시스템을 적용한 초고층건물의 거동을 효율적으로 해석할 수 있는 기법을 제안하여 다이어그리드 메가프레임 초고층건물의 해석과 설계에 소요되는 시간과 노력을 줄이고자 한다. 이를 위하여 다이어그리드 메가프레임의 특정을 활용한 효율적인 모형화기법과 행렬응축기법을 사용하여 해석에 사용되는 자유도수를 최소화한 해석기법을 제안하였다. 예제구조물의 해석을 수행하여 본 연구에서 제안된 해석방법과 일반적인 해석방법에 의한 결과와 비교함으로써 제안된 방법의 효율성과 정확성을 검증하였다.

• 대한토목학회논문집
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• 제12권4_1호
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• pp.9-21
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• 1992

논문에서는 주구조물의 기초와 부구조물의 지지점에 설치된 감진장치가 구조물의 지진응답 감소에 미치는 영향을 분석하였다. 여러가지 지진하중의 특성에 따른 감진장치가 설치된 주구조물과 부구조물의 거동을 비교분석하였으며, 이때 사용된 해석모델은 고정기초 구조물에 지지점이 고정된 부구조물, 감진기초 구조물에 지지점이 고정된 부구조물, 고정기초 구조물에 지지점 감진장치가 설치된 부구조물과 같은 세가지이다. 부구조물의 응답계산에서는 주구조물과 부구조물의 상호작용을 고려하였다. 계산에 사용한 수치적분방법은 constant average acceleration 방법이며, 이 방법과 축소행렬방법을 이용한 전산프로그램(KBISAP)을 사용하였다. 또한 지진하중에 대한 구조물의 지면에 대한 상대변위를 제한시키기 위하여 여러가지 지진하중에 대한 구조물의 가속도와 변위의 상관관계를 계산하여 감진장치의 적합한 수평강성을 분석하였다.

• Structural Engineering and Mechanics
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• 제13권5호
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• pp.557-568
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• 2002

For the evaluation of the capability of a tubular member of an offshore structure to absorb the collision energy, a simple method can be employed for the collision analysis without performing the detailed analysis. The most common simple method is the rigid-plastic method. However, in this method any characteristics for horizontal movement and rotation at the ends of the corresponding tubular member are not included. In a real structural system of an offshore structure, tubular members sustain a certain degree of elastic support from the adjacent structure. End fixity has influences in the behaviors of a tubular member. Three-dimensional FEM analysis can include the effect of end fixity fully, however in viewpoints of the inherent computational complexities of the 3-D approach, this is not the recommendable analysis at the initial design stage. In this paper, influence of end fixity on the behaviors of a tubular member is investigated, through a new approach and other approaches. A new analysis approach that includes the flexibility of the boundary points of the member is developed here. The flexibility at the ends of a tubular element is extracted using the rational reduction of the modeling characteristics. The property reduction is based on the static condensation of the related global stiffness matrix of a model to end nodal points of the tubular element. The load-displacement relation at the collision point of the tubular member with and without the end flexibility is obtained and compared. The new method lies between the rigid-plastic method and the 3-demensional analysis. It is self-evident that the rigid-plastic method gives high strengthening membrane effect of the member during global deformation, resulting in a steeper slope than the present method. On the while, full 3-D analysis gives less strengthening membrane effect on the member, resulting in a slow going load-displacement curve. Comparison of the load-displacement curves by the new approach with those by conventional methods gives the figures of the influence of end fixity on post-yielding behaviors of the relevant tubular member. One of the main contributions of this investigation is the development of an analytical rational procedure to figure out the post-yielding behaviors of a tubular member in offshore structures.

• 한국강구조학회 논문집
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• 제23권5호
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• pp.535-546
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• 2011

본 연구에서는 다양한 명시적 호장법을 사용하여 공간프레임의 반강접 탄소성 후좌굴 해석을 수행하였다. 이를 위해 이전 연구를 발전시켜 다양한 명시적 알고리즘의 호장법과 명시적, 묵시적 해석법에 동시에 적용 가능한 반강접 탄소성 공간프레임요소를 제안하였다. 다양한 명시적 호장법은 예측단계와 수렴단계에 명시적 해석법인 동적이완법을 적용한 것을 의미한다. 따라서 명시적 호장법에는 명시적(예측단계)-명시적(예측단계) 호장법, 명시적(예측단계)-묵시적(수렴단계) 호장법, 묵시적(예측단계)-명시적(수렴단계) 호장법으로 구분된다. 또한 명시적 호장법에 적용 가능하도록 수정된 반강접 탄소성 공간프레임요소는 오일러리안 유한변형이론에 의해 강체회전변형을 고려하였기 때문에 대변위가 발생하는 기하학적 비선형 문제에 적용될 수 있고, 완전 탄소성 소성힌지 알고리즘에 의한 재료적 비선형성을 고려하였으며, 부재내부에 정적 응축된 회전 및 축방향 성분의 선형 스프링에 의해 접합부 반강접 특성을 반영하였다. 제안된 해석법을 이용하여 검증예제를 수행함으로써 본 연구에서 제안된 다양한 명시적 호장법 및 공간프레임요소의 정확성을 검증한다.