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풍하중을 받는 평면 막구조물의 동적불안정 판정에 관한 연구
한상을,후효무,Han, Sung-Eul,Hou, Xiao-Wu 한국전산구조공학회 2009 한국전산구조공학회논문집 Vol.22 No.2
본 논문에서는 풍하중을 받는 평면 막구조물의 동적불안정 판정을 규명하였다. 풍하중을 받는 막구조물의 지배방정식을 정식화할 경우 가장 중요한 것은 막 표면의 공기 압력을 합리적으로 산정하는 것이다. 베르누이 윈리에 의하여 유체 압력은 속도 퍼텐셜과 관계를 가지며 않은 날개 원리에 의해 막 표면 공기의 움직임을 일련의 와류로 간주하고 속도 퍼텐셜을 구할 수 있다. 이 논문에서는 가장 많이 쓰이는 3 절점 삼각형 막요소를 이용하여 가중 잔여치 갤러킨법을 적용한 안정 평가의 판별식을 유도하였다. 수치해석 모델로는 정사각형과 직사각형의 막구조물을 채택하였고 임계 풍속에 대한 초기인장력과 풍방향의 영향을 분석하였다. In this paper, dynamic instability of plane membrane structures under wind action has been studied. The key to solving the governing equations of membrane structures under wind action is how to obtain the air pressure on membrane. Based on Bernoulli's theorem, fluid pressure has a certain relationship with velocity potential. Velocity potential could be solved according to thin aerofoil theory, where air around the membrane is regarded as a sheet of vortices. In this paper, we take advantage of the most commonly used three-node triangular membrane element and weighted residual-Galerkin method to obtain the determining equation for stability evaluation. Square and rectangular membrane structures are studied. The influence of initial prestressing force and wind direction towards critical wind velocity are also analyzed in this paper.
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Damping Identification Analysis of Membrane Structures under the Wind Load by Wavelet Transform
한상을,후효무 대한건축학회 2009 Architectural research Vol.11 No.1
In this paper, we take advantage of Wavelet Transform to identify damping ratios of membrane structures under wind action. Due to the lightweight and flexibility of membrane structures, they are very sensitive to the wind load, and show a type of fluid-structure interaction phenomenon simultaneously. In this study, we firstly obtain the responses of an air-supported membrane structure by ADINA with the consideration of this characteristic, and then conduct Wavelet Transform on these responses. Based on the Wavelet Transform, damping ratios could be obtained from the slope of Wavelet Transform in a semi-logarithmic scale at a certain dilation coefficient. According to this principle, damping ratios could eventually be obtained. There are two numerical examples in this study. The first one is a simulated signal, which is used to verify the accuracy of the Wavelet Transform method. The second one is an air-supported membrane structure under wind action, damping ratios obtained from this method is about 0.05~0.09. The Wavelet Transform method could be regarded as a very good method for the the damping analysis, especially for the large spatial structures whose natural frequencies are closely spaced.
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Dynamic Instability of Lattice-Dome Structures by Lyapunov Concept
한상을,후효무 대한건축학회 2008 Architectural research Vol.10 No.1
Stability is a very important part which we must consider in structural design. In this paper, we take advantage of finite element method to study parametrical instability of lattice dome structures, which is subjected to harmonically pulsating load. We consider elastic stiffness and geometrical stiffness simultaneously during the calculation of stiffness matrix, and adopt consistent mass matrix to make the solution more correct. In order to obtain instability regions, we represent displacements and accelerations in dynamic equation by trigonometric series expansions, and then obtain Hill’s infinite determinants. After first order approximation, we can get first and second order dynamic instability regions eventually. Finally, we take 24-bar star dome and 90-bar lamella dome as examples to investigate dynamic instability phenomena.
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풍하중을 받는 이중곡률 막구조물의 동적불안정 현상에 관한 연구
한상을(Han Sang-Eul),후효무(Hou Xiao-Wu) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.4
In this paper, dynamic instability problem of doubly curved membrane structures has been studied. The key point to solve the governing equations of membrane structures under wind action is how to obtain the air pressure on membrane structures. Based on Bernoulli’s theorem, fluid pressure has a certain relationship with velocity potential. Velocity potential could be solved according to thin aerofoil theory, where air around the membrane is regarded as a sheet of vortices. In this paper, we take advantage of the most commonly used three-node triangular membrane element and weighted residual-Galerkin method to obtain the determining equation for stability evaluation. The influence of initial prestressing force, wind direction angle and curvature towards critical wind velocity are also analyzed in this paper.
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