더블앵글 접합부는 저층 철골조에 많이 사용된다. 본 연구에서는 더블앵글 접합부에 사용된 볼트의 개수 변화가 접합부 회전강성 변화에 미치는 영향을 시험을 통하여 파악하고, 모멘트-회전각 관계 곡선의 회귀분석을 통하여 초기강성, 소성강성, 참조모멘트, 곡선형태변수 등을 획득하였다. 또한 더블앵글 접합부의 초기강성이 접합부의 모멘트 지지능력을 파악하는데 매우 중요한 변수라는 것이 밝혀졌기 때문에 이러한 초기강성 산정을 위한 해석모델도 제안하였다.
Walking loads are usually considered as nodal loads in the finite element vibration analysis of structures subjected to walking loads. Since most of the walking loads act on elements not nodes, the walking loads applied on the elements should be converted to the equivalent nodal walking loads. This paper begins with measuring walking loads by using a force plate equipped with load cells and investigates the characteristics of the walking loads with various walking rates. It is found that the walking loads are more affected by walking rates than other parameters such as pedestrian weight, type of footwear, surface condition of floor etc. The measured walking loads are used as input loads for a finite element model of walking induced vibration. Finally, this paper proposes the equivalent nodal walking loads that are converted from the walking loads acting on elements based on finite element shape functions. And the proposed equivalent walking loads are proved to be applicable for efficient analysis of floor vibration induced by walking loads.
Researches on spherical shell which is most usually applied have been completed by many investigators already and generalized numerical formula was derived. But the existent researches are limited to those on spherical shell with isotropic or orthotropic roof stiffness, periodic distribution of roof stiffness that can be caused by spherical and latticed roof system is not considered. Therefore, the object of this study is to develop a structural analysis program to analyze spherical shells that have periodicity of roof stiffness distribution caused by latticed roof of large space structure, grasp buckling characteristics and behavior of structure.
A frame element embedded normal to a shear wall or slab (shell element) is common in the structural systems. In that case there is a need for a membrane or shell element to have a normal rotation degree of freedom at each node in order to have a good result of stresses. Even if Many other people studied this area, All man, Cook and Sabir are representative investigators in this area. In this research paper, Sabir's methods of vertex rotation stiffness matrix in a membrane element are studied. New stiffness of vertex rotation are proposed by taking advantage of beam stiffness theory. Rectangular elements stiffness with rotational degree of freedom are compared in accuracy ratio each other.
유전자 알고리즘은 가장 훌륭한 이산최적화 기법 중 하나이다. 그러나, 유전자 알고리즘은 무제약 최적화 기법이기 때문에 제약조건은 간접적으로 표현된다. 가장 일반적인 방법은 벌칙함수를 사용하여 제약 문제를 무제약 문제로 변환하는 것이다. 본 연구에서는 적합도에 벌점함수를 적용하여 거부전략, 벌점전략, 복합전략 등에 따른 3가지 함수를 구성하였다. 그리고, 이 적합도 함수들을 사용한 설계프로그램을 구현하고, 산형골조와 2층 3경간 골조의 설계문제에 적용시켜 설계결과를 비교하였다. 이를 통하여 유전자 알고리즘을 이용한 유용한 골조 설계프로그램의 구현이 가능할 것으로 판단된다.
An exact solution procedure is formulated for the free vibration and buckling analysis of rectangular plates having two opposite edges simply supported when these edges are subjected to linearly varying normal stresses. The other two edges may be clamped, simply supported or free, or they may be elastically supported. The transverse displacement (w) is assumed as sinusoidal in the direction of loading (x), and a power series is assumed in the lateral (y) direction (i.e., the method of Frobenius). Applying the boundary conditions yields the eigenvalue problem of finding the roots of a fourth order characteristic determinant. Care must be exercised to obtain adequate convergence for accurate vibration frequencies and buckling loads, as is demonstrated by two convergence tables. Some interesting and useful results for vibration frequencies and buckling loads, and their mode shapes, are presented for a variety of edge conditions and in-plane loadings, especially pure in-plane moments.
A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies and mode shapes of solid paraboloidal and complete (that is, without a top opening) paraboloidal shells of revolution with variable wall thickness. Unlike conventional shell theories, which are mathematically two-dimensional (2-D), the present method is based upon the 3-D dynamic equations of elasticity. The ends of the shell may be free or may be subjected to any degree of constraint. Displacement components ur, uθ, and uz in the radial, circumferential, and axial directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the r and z directions. Potential (strain) and kinetic energies of the paraboloidal shells of revolution are formulated, and the Ritz method is used to solve the eigenvalue problem, thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four digit exactitude is demonstrated for the first five frequencies of the complete, shallow and deep paraboloidal shells of revolution with variable thickness. Numerical results are presented for a variety of paraboloidal shells having uniform or variable thickness, and being either shallow or deep. Frequencies for five solid paraboloids of different depth are also given. Comparisons are made between the frequencies from the present 3-D Ritz method and a 2-D thin shell theory.
Almost the steel bridges are manufactured and constructed by using weld process. The welding is necessary for connecting the flange, web and stiffener of steel bridges. However, residual stress and welding deformation producted by welding is a causes of decreasing the load carrying capacity of steel bridges. therefore, it is need to consider the initial stresses by welding when design the steel bridge. However, the influence of initial stress producted by welding on load carrying capacity of steel bridges is not elucidated. In this paper, the initial stress state on the flange, web and stiffener of steel bridges are clarified by carrying out 3-dimensional non-steady heat conduction analysis and 3-dimensional thermal elastic-plastic analysis. The influence of initial stress by welding on load carrying capacity of steel bridges is clarified by carrying out 3-dimensional elastic-plastic finite element analysis using finite deformation theory.
Recently, as steel structures become higher and more long-spanned, application of high-strength steels is increasing gradually. However, criteria and example for design of high-strength steel are not built up. exiting criteria for structural steels is not proper for economical design of high-strength steel. Moreover, exiting criteria will be decrease the fatigue performance of steel bridge using high-strength steel. Therefore, criterion for application of high-strength steel must be established. In this paper, the behavior of plate girder using high-strength vertical stiffeners was clarified by carrying out layer elastic-plastic finite element analysis using finite deformation theory. In order to optimize the design and construction of plate girder using high-strength vertical stiffener, criterion for application of high-strength vertical stiffener is proposed.