• Structural Engineering and Mechanics
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• 제22권5호
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• pp.575-597
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• 2006

Enhanced three-dimensional finite elements for geometrically nonlinear analysis of cable-supported structures are presented. The cable element, derived by using the concept of an equivalent modulus of elasticity and assuming the deflection curve of a cable as catenary function, is proposed to model the cables. The stability functions for a frame member are modified to obtain a numerically stable solution. Various numerical examples are solved to illustrate the versatility and efficiency of the proposed finite element model. It is shown that the finite elements proposed in this study can be very useful for geometrically nonlinear analysis as well as free vibration analysis of three-dimensional cable-supported structures.

• 한국전산구조공학회논문집
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• 제13권3호
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• pp.373-384
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• 2000

단기 동 하중(특히 지진하중)을 받는 비선형 강 프레임 구조물의 안전성을 평가하기 위하여 추계론적 유한요소 개념에 근거한 비선형 시간영역 신뢰성 해석 기법을 제안하였다. 제안된 알고리즘에서는 유한요소 공식화가 응답 표면법, 1차 신뢰성 방법, 그리고 반복 선형보간 기법의 개념들과 결합되어 지는데, 이것이 추계론적 유한요소 개념으로 귀결된다. 실제 지진하중의 시간이력이 구조물의 진동을 위해 사용되므로 사실적인 하중조건의 재현이 가능하다. 가상 응력에 기초한 유한요소 기법이 본 알고리즘의 효율성을 증대하기 위해 사용된다. 본 알고리즘은 지진하중 또는 임의의 단기 동적하중을 받는 유한요소 기법으로 표현되는 어떠한 선형 및 비선형 구조물과 관련된 위험도를 평가할 수 있는 잠재성을 가지고 있다. 수치예제를 통하여 알고리즘을 설명하였으며, 몬테카를로 시뮬레이션 기법을 사용하여 본 알고리즘을 검증하였다.

• Computational Structural Engineering : An International Journal
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• 제1권2호
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• pp.107-116
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• 2001

The present paper investigates the nonlinear behavior of reinforced concrete shear walls with a crank based on a finite element analysis. The loading type is a horizontal cyclic one such as earthquake loads. Experiments of the shear walls with and without cranks, performed previously to see flow the behavior changes depending on the crank, are compared with the results obtained from the finite element analysis. The finite element analysis is based on an isoparametric degenerated shell formulation. The nonlinear constitutive equations fur concrete are modeled adopting the formulation based on a concept of Ring Typed-Lattice Model. The experiments indicate that the shear walls with a crank have low stiffness and relatively low carrying capacity compared with an ordinary plane shear wall without cranks and that they are more ductile, and the tendency is a1so confirmed based on the finite element analysis. Moreover, a good agreement between the experiments and analyses is obtained, accordingly, it is confined that the present numerical analysis scheme based on the Lattice Model is a powerful one to evaluate the behavior of reinforced concrete shear walls with cranks and without cranks.

• 전산구조공학
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• 제8권3호
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• pp.79-89
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• 1995

본 논문에서는 평판 두께 방향의 선형 및 비선형 응력 분포를 일정한 크기의 단순응력 상태로 가정하는 분할판(Two-element plate) 개념을 이용하여 비선형 특성을 나타내는 평판의 강도해석을 할 수 있는 Reissner 범함수와, 재질 특성은 선형이면서 기하학적 비선형 특성만을 갖는 평판의 강도해석을 할 수 있는 변형 Reissner 범함수를 모델링하였다. 두 종류의 Reissner 범함수들을 근거로 하여 축방향 하중을 받는 평판의 선형 좌굴과 좌굴후의 비선형 특성 및 최대강도들을 계산할 수 있는 유한요소 방정식과 프로그램 개발을 시도하였다. 개발한 프로그램을 이용한 수치해석 결과, 분할판 이론을 사용한 선형좌굴해석 결과가 기존의 평판이론을 사용한 선형좌굴해석 결과와 유사항 경향을 나타냄으로써 분할판 이론에 근거한 유한요소법을 하중과 경계조건 및 구성재질이 다양한 일반적인 평판의 강도해석에 확대 적용함은 물론 좌굴후 비선형재질 특성으로 인한 평판의 최대강도도 예측 가능하다고 생각한다.

• Computers and Concrete
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• 제3권2_3호
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• pp.123-144
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• 2006

Reinforced concrete corbels are structural elements widely used in practical engineering. The complex response of these elements is described in design codes in a simplified manner. These formulations are not sufficient to show the real behavior, which, however, is an essential prerequisite for the manufacturing of numerous elements. Therefore, a deterministic and probabilistic study has been performed, which is described in this contribution. Real complex structures have been modeled by means of the finite element method supported primarily by experimental works. The main objective of this study was the detection of uncertainties effects and safety margins not captured by traditional codes. This aim could be fulfilled by statistical considerations applied to the investigated structures. The probabilistic study is based on advanced Monte Carlo simulation techniques and sophisticated nonlinear finite element formulations.

• 한국전산구조공학회논문집
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• 제23권6호
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• pp.659-665
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• 2010

The finite element method(FEM) is proven to be an effective approximate method of structural analysis if proper element types and meshes are chosen, and recently, the method is often applied to solve complex dynamic and nonlinear problems. A properly chosen element type and mesh yields reliable results for dynamic finite element structural analysis. However, dynamic behavior of a structure may include unpredictably large strains in some parts of the structure, and using the initial mesh throughout the duration of a dynamic analysis may include some elements to go through strains beyond the elements' reliable limits. Thus, the finite element mesh for a dynamic analysis must be dynamically adaptive, and considering the rapid process of analysis in real time, the dynamically adaptive finite element mesh generating schemes must be computationally efficient. In this paper, a computationally efficient dynamically adaptive finite element mesh generation scheme for dynamic analyses of structures is described. The concept of representative strain value is used for error estimates and the refinements of meshes use combinations of the h-method(node movement) and the r-method(element division). The shape coefficient for element mesh is used to correct overly distorted elements. The validity of the scheme is shown through a cantilever beam example under a concentrated load with varying values. The example shows reasonable accuracy and efficient computing time. Furthermore, the study shows the potential for the scheme's effective use in complex structural dynamic problems such as those under seismic or erratic wind loads.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 봄 학술발표회 논문집
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• pp.47-52
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• 1992

The entire nonlinear behavior of reinforced concrete frames up to collapse, is analyzed by the displacement control method and the combined layered and nonlayered method. All of the rigidities of section are calculated approximately by a sum over all the layers for the layered method, are used the integral values over the cross section area for the nonlayered method. The spurious sensitivity to the chosen element size in the result of analysis by finite element method for the materials with strain-softening can be overcome by modifying the strain distribution based on the concept of fracture energy at plastic hinge considering the applied axial load.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.442-449
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• 2004

This paper describes a new concept of finite element analysis, which is based on neural network based material models (NNCMs) without invoking any pre-chosen mathematical framework. NNCMs have several advantages over conventional constitutive models (CCMs) and once plugged in a finite element (FE) engine, can be used for FE analysis in a manner similar to CCMs. The paper demonstrates a FE framework in which NNCMs are incorporated and also proposes a strategy for data enhancement by invoking the assumption of isotropy of the material. It is shown through some illustrative examples that this provides a better training environment for a generalized NNCM in which stress and strain components are used as effects and cause. Form this study, it appears that there is a prima facia case for developing NNCMs for materials for which mathematical theories become too complex and a large number of material parameters and constants have to be identified or determined.

• 대한조선학회논문집
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• 제57권2호
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• pp.70-79
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• 2020

The offshore installation units may be subjected to various accidental loads such as collision from supply vessels, impact from dropped objects, blast load from gas explosion and thermal load from fire. This paper deals with the design and strength evaluation method of the stiffened plate structures in response to a blast load caused by a gas explosion accident. It is a comprehensive review of various items used in actual project such as the size and type of the explosive loads, general design procedure/concept and analysis method. The structural analyses using simple analysis methods based on SDOF model and nonlinear finite element analysis are applied to the particular FPSO project. Also validation studies on the design guidance given by simple analysis method based on SDOF model have also considered several items such as backpressure effects, material behavior and duration time of the overpressure. A good correlation between the prediction made by simple analysis method based on SDOF model and nonlinear finite element analysis can be generally obtained up to the elastic limit.

• Computers and Concrete
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• 제2권3호
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• pp.215-238
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• 2005

This work is based on a nonlinear finite-element model with proven capacity for yielding realistic predictions of the response of reinforced-concrete structures under static monotonically-increasing loading. In it, the material description relies essentially on the two key properties of triaxiality and brittleness and, thus, is simpler than those of most other material models in use. In this article, the finite-element program is successfully used in investigating the behaviour of a series of RC walls under static cyclic loading. This type of loading offers a more strenuous test of the validity of the proposed program since cracks continuously form and close during each load cycle. Such a test is considered to be essential before attempting to use the program for the analysis of concrete structures under seismic excitation in order to ensure that the solution procedure adopted is numerically stable and can accurately predict the behaviour of RC structures under such earthquake-loading conditions. This is achieved through a comparative study between the numerical predictions obtained presently from the program and available experimental data.