• 한국강구조학회 논문집
• /
• 제14권6호
• /
• pp.793-802
• /
• 2002

수평곡선 I형교에 동적해석을 수행하기 위하여 박판곡선보 이론에 근거 뒴자유도를 포함한 절점당 7자유도를 갖는 곡선보요소와 7자유도 직선보요소를 사용하여 동적해석프로그램 EQCVB를 작성하였다. 이 프로그램에서는 자유진동해석을 위하여 Gupta의 방법을 사용하였고, 지진하중이 작용할 때 동적해석을 수행하기 위하여 Wilson-${\theta}$방법을 사용하였으며, 범용구조해석 프로그램인 ABAQUS를 사용한 해석 결과와 비교하여 프로그램의 효율성과 타당성을 입증하였다. 지진하중 작용시 수평곡선 I형교의 동적 거동 특성을 파악하기 위하여 다양한 예제에 대한 해석을 수행하였다.

• 한국강구조학회 논문집
• /
• 제10권1호통권34호
• /
• pp.47-61
• /
• 1998

수평곡선 I형교에서는 곡선주형의 초기곡률로 인하여 휨과 비틀림이 서로 연성 되어 복잡한 거동을 하며. 교량전체 거동에 가로보가 미치는 영향이 상당히 크다. 수평곡선 I형교의 거동특성을 파악하기 위해서는 곡선주형과 함께 가로보를 고려하여야 한다. 본 연구에서는 수평곡선 I형교에 대한 자유진동해석을 위하여 곡선주형을 유한요소 모델링하기 위한 곡선보요소와 가로보를 모델링하기위한 직선보요소를 구성하고, 이들 보요소를 사용한 유한요소 해석 프로그램을 개발한다. 곡선보 요소는 초기곡률과 됨을 고려하기 위하여 박판곡선보 이론에 근거하여 2축 대칭단면을 갖는 I형 곡선보에 대한 유한요소 정식화를 통하여 구성되며, 이때 형상함수는 박판곡선보의 선형 정적 평형방정식의 제차해를 사용한다. 직선보 요소는 됨자유도를 포함하여 절점당 7자유도를 갖는다. 개발한 프로그램에서는 직교좌표계를 사용하여 전체 강성행렬과 전체 질량행렬을 구성하며, 고유치를 구하기 위하여 Gupta의 방법을 사용한다. 기존의 연구결과를 이용하여 구성된 곡선보 요소를 비교검증하고, 수치해석 예제를 통하여 개발한 프로그램의 결과와 쉘요소를 사용하여 범용유한요소해석프로그램으로 수행한 결과를 비교한다.

• Steel and Composite Structures
• /
• 제27권1호
• /
• pp.1-12
• /
• 2018

This paper presents a semi-analytical solution of simply supported horizontally composite curved I-beam by trigonometric series. The flexibility of the interlayer connectors between layers both in the tangential direction and in the radial direction is taken into account in the proposed formulation. The governing differential equations and the boundary conditions are established by applying the variational approach, which are solved by applying the Fourier series expansion method. The accuracy and efficiency of the proposed formulation are validated by comparing its results with both experimental results reported in the literature and FEM results.

• Structural Engineering and Mechanics
• /
• 제88권1호
• /
• pp.83-94
• /
• 2023

An accurate and highly efficient inverse element labelled iPCB is developed based on the inverse finite element method (iFEM) for real-time shape estimation of plane-curved structures (such as arch bridges) utilizing onboard strain data. This inverse problem, named shape sensing, is vital for the design of smart structures and structural health monitoring (SHM) procedures. The iPCB formulation is defined based on a least-squares variational principle that employs curved Timoshenko beam theory as its baseline. The accurate strain-displacement relationship considering tension-bending coupling is used to establish theoretical and measured section strains. The displacement fields of the isoparametric element iPCB are interpolated utilizing nonuniform rational B-spline (NURBS) basis functions, enabling exact geometric modelling even with a very coarse mesh density. The present formulation is completely free from membrane and shear locking. Numerical validation examples for different curved structures subjected to different loading conditions have been performed and have demonstrated the excellent prediction capability of iPCBs. The present formulation has also been shown to be practical and robust since relatively accurate predictions can be obtained even omitting the shear deformation contributions and considering polluted strain measures. The current element offers a promising tool for real-time shape estimation of plane-curved structures.

• Steel and Composite Structures
• /
• 제26권5호
• /
• pp.607-620
• /
• 2018

Vibration analysis of deep curved FG nano-beam has been carried out based on modified couple stress theory. Material properties of curved Timoshenko beam are assumed to be functionally graded in radial direction. Governing equations of motion and related boundary conditions have been obtained via Hamilton's principle. In a parametric study, influence of length scale parameter, aspect ratio, gradient index, opening angle, mode number and interactive influences of these parameters on natural frequency of the beam, have been investigated. It was found that, considering geometrical deepness term leads to an increase in sensitivity of natural frequency about variation of aforementioned parameters.

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

• 한국해양공학회지
• /
• 제24권5호
• /
• pp.88-93
• /
• 2010

Many pipes that are arranged longitudinally in ships have loops at intervals to prevent the failure of the pipes as they absorb large portions of the axial load caused by the bending of the hull girder and/or thermal loads when the pipes are carrying very hot fluids. Since the loops are curved at corners, an efficient method for conducting the structural analyses of these curved portions is required. In this paper, a pipe loop was analyzed by an analytical method and by the finite-element method in four different ways, i.e., based on straight-beam elements, curved-beam elements, 2-D shell elements, and 3-D solid elements. The results of the five analyses were compared to check the validity of the current curved-beam theory. The paper includes some suggestions on how to analyze the pipe loops efficiently.

• Advances in aircraft and spacecraft science
• /
• 제11권1호
• /
• pp.55-81
• /
• 2024

This paper presents the exact solutions and closed forms for of nonlinear stability and vibration behaviors of straight and curved beams with nonlinear viscoelastic boundary conditions, for the first time. The mathematical formulations of the beam are expressed based on Euler-Bernoulli beam theory with the von Karman nonlinearity to include the mid-plane stretching. The classical boundary conditions are replaced by nonlinear viscoelastic boundary conditions on both sides, that are presented by three elements (i.e., linear spring, nonlinear spring, and nonlinear damper). The nonlinear integro-differential equation of buckling problem subjected to nonlinear nonhomogeneous boundary conditions is derived and exactly solved to compute nonlinear static response and critical buckling load. The vibration problem is converted to nonlinear eigenvalue problem and solved analytically to calculate the natural frequencies and to predict the corresponding mode shapes. Parametric studies are carried out to depict the effects of nonlinear boundary conditions and amplitude of initial curvature on nonlinear static response and vibration behaviors of curved beam. Numerical results show that the nonlinear boundary conditions have significant effects on the critical buckling load, nonlinear buckling response and natural frequencies of the curved beam. The proposed model can be exploited in analysis of macrosystem (airfoil, flappers and wings) and microsystem (MEMS, nanosensor and nanoactuators).

• 한국재난정보학회 논문집
• /
• 제14권3호
• /
• pp.379-386
• /
• 2018

연구목적: 본 연구는 I-Shape 단면형상을 가지고 있는 곡선교량의 지진파 불확실성에 따른 안전성 분석을 위해 확률론적 기반 취약도 평가를 목적으로 한다 연구방법: 상용유한요소해석 프로그램(ABAQUS, ANSYS)구축된 모델의 검증을 위해 토크와 집중하중을 적용하여 정적해석에 따른 해석결과와 이론해를 곡선 보의 1/4L, 2/4L, 3/4L 지점에서 휨 모멘트를 비교한 결과 모든 지점에서 1%내로 오차가 발생하는 것으로 나타나 3차원 유한요소 모델에 대한 신뢰성을 확보 하였다. 곡선교량 구조물의 지진파의 불확실성을 위해 경주 및 포항 지진을 포함하여 세계각지에서 발생한 20개의 지진파를 0.2g부터 1.5g까지 5개의 Scale로 변화시켜 시간이력해석을 수행하였으며, Monte-Carlo Simulation을 기반으로 지진 취약도 평가를 수행하였다. 연구결과: 지진 취약도 분석결과 한계상태를 190MPa로 하였을 때 0.2g를 넘어가면서 파괴가 발생하나 한계상태를 315MPa로 하였을 경우 0.6g를 넘어서면서 파괴가 발생하는 것으로 나타났다. 결론: 본 연구에서 이론해와 수치해석 모델을 비교함으로써 유한요소 모델을 검증하였으며 구축된 I-Shape 곡선 보 모델의 경우 고주파수 영역에 민감성을 보이며, 추후 연구에서 곡선 보의 주요 매개변수인 단면형상에 따른 지진 취약도 평가를 수행하고자 한다.

• 한국안전학회지
• /
• 제13권3호
• /
• pp.163-170
• /
• 1998

I-단면 곡선보(curved beam)의 뒤틀림(warping)을 포함한 평면외(out-of-plane)의 자유진동을 해석하는데 differential quadrature method(D.Q.M.)을 이용하여 다양한 경계조건(boundary conditions)과 굽힘각(opening angles)에 따른 진동수(frequencies)를 계산하였다. D.Q.M.의 결과는 해석적 해답(exact solution) 또는 다른 수치해석(Rayleigh-Ritz 또는 FEM) 결과와 비교하였으며, D.Q.M.은 적은 요소(grid points)를 사용하여 정확한 해석결과를 보여주었다.