직교화 기법을 이용한 앙상블 경험적 모드 분해법의 고유 모드 함수와 모드 직교성

손수덕,하준홍,비자야 P. 포크렐,이승재,Shon, Sudeok,Ha, Junhong,Pokhrel, Bijaya P.,Lee, Seungjae 한국공간구조학회 2019 한국공간구조학회지 Vol.19 No.2

In this paper, the characteristic of intrinsic mode function(IMF) and its orthogonalization of ensemble empirical mode decomposition(EEMD), which is often used in the analysis of the non-linear or non-stationary signal, has been studied. In the decomposition process, the orthogonal IMF of EEMD was obtained by applying the Gram-Schmidt(G-S) orthogonalization method, and was compared with the IMF of orthogonal EMD(OEMD). Two signals for comparison analysis are adopted as the analytical test function and El Centro seismic wave. These target signals were compared by calculating the index of orthogonality(IO) and the spectral energy of the IMF. As a result of the analysis, an IMF with a high IO was obtained by GSO method, and the orthogonal EEMD using white noise was decomposed into orthogonal IMF with energy closer to the original signal than conventional OEMD.

돔형 스페이스 프레임 구조물의 하중모드에 따른 분기점 특성에 관한 연구

손수덕,김승덕,이승재,김종식 한국공간구조학회 2011 한국공간구조학회지 Vol.11 No.1

스페이스 프레임 구조물은 연속체 쉘 구조물의 원리를 이용하여 매우 넓은 공간을 효과적 으로 덮을 수 있는 구조물이지만 뜀좌굴 및 분기좌굴 등과 같은 불안정거동은 돔형 구조물에서는 더욱 복잡하게 나타난다. 또한 붕괴메커니즘의 이론적 연구와 실험적 연구결과들 사이에서도 많은 차이를 보인다. 본 논문에서는 미적 효과가 크며 단층의 대공간을 확보하기에 적합한 돔형 공간 구조물의 구조 불안정 특성을 접선강성방정식을 이용하여 비선형 증분해석을 수행하고, Rise-span(μ)비 및 하중모드(RL)에 따른 임계점과 분기점의 특성을 돔형 공간구조물의 예제를 통해 고찰하였다. 여기서 불안정점은 증분해석과정을 통해서 예측할 수 있었으며, 예제에서 낮은 μ에서는 전체좌굴이, 높은 μ의 경우는 절점좌굴이 지배적이며, 낮은 RL에서 정점좌굴이, 높은 RL에서는 전체좌굴이 지배적이고, 전체좌굴이 나타나는 경우, 분기좌굴하중은 완전형상의 극한점좌굴하중의 약 50%에서 70%의 분포를 보였다. Space frame structures have the advantage of constructing a large space structures without column and it may be considered as a shell structure. Nevertheless, with the characteristics of thin and long term of spacing, the unstable problem of space structure could not be set up clearly, and there is a huge difference between theory and experiment. Therefore, in this work, the tangential stiffness matrix of space frame structures is studied to solve the instability problem, and the nonlinear incremental analysis of the structures considering rise-span ratio(μ) and the ratio of load(RL) is performed for searching unstable points. Basing on the results of the example, global buckling can be happened by low rise-span ratio(μ), nodal buckling can be occurred by high rise-span ratio(μ). And in case of multi node space structure applying the ratio of load(RL), the nodal buckling phenomenon occur at low the ratio of load(RL), the global buckling occur a1 high the ratio of load(RL). In case of the global buckling, the load of bifurcation is about from 50% to 70% of perfect one's snap-through load.

얕은 공간트러스 돔의 구조안정성과 설계

손수덕,최서원,하현주,이돈우,곽의신,Shon, Su-Deok,Choi, Seo-Woen,Ha, Hyun-Ju,Lee, Don-Woo,Kwak, Eui-Shin 한국공간구조학회 2016 한국공간구조학회지 Vol.16 No.2

단일공기막 구조물의 설계하중에 따른 비선형 응력-변형 해석 및 설계에 관한 연구

손수덕,정을석,김승덕,Shon, Su-Deok,Jeong, Eul-Seok,Kim, Seung-Deog 한국공간구조학회 2005 한국공간구조학회지 Vol.5 No.2

공기막구조물의 공간형성방법은 크게 단일공기막과 이중공기막 방식으로 나뉜다. 내압으로 인해 평형곡면이 형성되는 공기막구조물의 형상은 형태의 변화가 외력에 의해 크게 변형되거나 응력이 집중되지 않는 등장력 곡면으로 많이 이용된다. 따라서 본 연구에서는 공기막 구조물의 초기 형성된 형상에 대해서 설계하중조합에 대한 구조해석을 비선형 전용해석프로그램인 NASS를 이용하여 수행한 후 변형형상을 살펴보고, 최대응력을 이용하여 안전성을 검토한다. 해석 모델은 사면에서 지지되는 장방형 단일공기막 구조물을 대상으로 하며, 직교이방성을 고려하여 비선형 증분해석을 수행한다. The method to form the space of the pneumatic structures by internal pressure is classified greatly as the dual type with the nlty type. The shape of the pneumatic structures consists of the curved surface under uniform tension not greatly to be deformed by the design load and stress must not be concentrated also. Therefore, In this study, we have done the structural analysis of the unity typed pneumatic structures by the NASS which is the program for nonlinear analysis. The analytic model is a rectangular pneumatic membrane structures which have four side fixed edges. And we have done the nonlinear incremental analysis considering the orthotropic material.

비선형 내력법을 이용한 단일 공기막의 형상 탐색

손수덕,하준홍,이승재,Shon, Sudeok,Ha, Junhong,Lee, Seungjae 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.4

This study aims to develop a form-finding algorithm for a single-layered pneumatic membrane. The initial shape of this pneumatic membrane, which is an air-supported type pneumatic membrane, is to find a state in which a given initial tension and internal pneumatic pressure are in equilibrium. The algorithm developed to satisfy these conditions is that a nonlinear optimization problem based on the force method considering the deformed shape is formulated, and, it's able to find the shape by iteratively repeating the process of obtaining a solution of the governing equations. An computational technique based on the Gauss-Newton method was used as a method for obtaining solutions of nonlinear equations. In order to verify the validity of the proposed form-finding algorithm, a single-curvature pneumatic membrane example and a double-curvature air pneumatic membrane example were adopted, respectively. In the results of these examples, it was possible to well observe the step-by-step convergence process of the shape of the pneumatic membrane, and it was also possible to confirm the change in shape according to the air pressure. In addition, the calculation results of the shape and internal force after deformation due to initial tension, air pressure, and self-weight were obtained.

주기 하중을 받는 3-자유절점 공간 트러스의 동적 불안정 현상과 주파수 특성

손수덕,황경주,Shon, Sudeok,Hwang, Kyung-Ju 한국공간구조학회 2020 한국공간구조학회지 Vol.20 No.4

The governing equation for a dome-type shallow spatial truss subjected to a transverse load is expressed in the form of the Duffing equation, and it can be derived by considering geometrical non-linearity. When this model under constant load exceeds the critical level, unstable behavior is appeared. This phenomenon changes sensitively as the number of free-nodes increases or depends on the imperfection of the system. When the load is a periodic function, more complex behavior and low critical levels can be expected. Thus, the dynamic unstable behavior and the change in the critical point of the 3-free-nodes space truss system were analyzed in this work. The 4-th order Runge-Kutta method was used in the system analysis, while the change in the frequency domain was analyzed through FFT. The sinusoidal wave and the beating wave were utilized as the periodic load function. This unstable situation was observed by the case when all nodes had same load vector as well as by the case that the load vector had slight difference. The results showed the critical buckling level of the periodic load was lower than that of the constant load. The value is greatly influenced by the period of the load, while a lower critical point was observed when it was closer to the natural frequency in the case of a linear system. The beating wave, which is attributed to the interference of the two frequencies, exhibits slightly more behavior than the sinusoidal wave. And the changing of critical level could be observed even with slight changes in the load vector.

막 구조물의 재단도 작성과 막재의 손실률에 관한 연구

손수덕,정을석,김승덕,Shon, Su-Deok,Jeong, Eul-Seok,Kim, Seung-Deog 한국공간구조학회 2006 한국공간구조학회지 Vol.6 No.1

경량 연성구조시스템 중 하나인 막 구조물은 대공간 구조물에 많이 사용되어진다. 막 구조물은 축강성이 강하고 휨강성이 매우 작은 재료를 주 구조재로 사용하기 때문에 다른 구조물과 달리 구조설계에서는 형상해석, 응력-변형해석 그리고 재단도 등의 일련의 과정을 필요로 한다. 재단도의 작성에는 구조물의 크기나 곡률 그리고 재료적 강성에 따라 많은 변수가 작용하며 다른 설계과정과는 매우 다르다. 따라서 일반 구조설계용 프로그램은 막 구조물의 구조설계에 부적당하다. 본 연구에서는 막 구조물의 측지선을 이용한 재단도 작성 프로그램을 개발하고, 예제를 통해 재단도 작성결과를 비교 고찰하도록 한다. Membrane structures, a kind of lightweight soft structural system, are used for spatial structures. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation, because the material property has strong axial stiffness, but little bending stiffness. The problem of cooing pattern is highly varied in their size, curvature and material stiffness. So, the approximation inherent in cutting pattern generation methods is quite different. Therefore the ordinary computer software of structural analysis & design is not suitable for membrane structures. In this study, we develop the program for cooing pattern generation using geodesic line, and investigate the result of example's cooing pattern in detail.

공기막 구조물의 형상과 형상 탐색 알고리즘

손수덕,하준홍,이승재,Shon, Sudeok,Ha, Junhong,Lee, Seungjae 한국공간구조학회 2021 한국공간구조학회지 Vol.21 No.3

막 구조물의 초기형상해석과 재단도 작성에 관한 연구

손수덕,정을석,김승덕,안상길 대한건축학회 2006 大韓建築學會論文集 : 構造系 Vol.22 No.5

Membrane structures, a kind of lightweight soft structural system, are many used for large spatial stadium or gymnasium. The material property of the membrane has strong tensional stiffness, but little bending. The design procedure of membrane structures are needed to do shape finding, stress-deformation analysis and cutting pattern generation. In shape finding, membrane structures are unstable structures initially. These soft structures need to be introduced initial stresses because of its initial unstable state, and happen large deformation phenomenon. Also there are highly varied in their size, curvature and material stiffness. So, the approximation inherent in cutting pattern generation methods is quite different.Therefore, in this study, to find the structural shape after large deformation caused by initial stress, we have done the shape analysis considering geometric nonlinear term. And the geodesic line on surface of initial equilibrium shape and the cutting pattern generation using the geodesic line is introduced.

형상에 따른 주름강판의 탄성전단좌굴 특성 및 경향성 분석 연구

손수덕,이승재,유미나 한국구조물진단유지관리공학회 2014 한국구조물진단유지관리공학회 논문집 Vol.18 No.6

This paper aims at comparing and analyzing shear buckling characteristics between sinusoidal corrugation shape and trapezoidalone. For this, I adopted the equal-length trapezoidal corrugation and sinusoidal one for the analytical models, and analyzed theirshear buckling characteristics through linear buckling analysis and on its theory. Generally, the shear buckling shapes of corrugatedsteel plates are classified into local buckling, global buckling, and interactive buckling from the two buckling modes. Sinusoidalcorrugation shape, unlike trapezoidal corrugation, does not have flat sides, which causes another tendency in shear buckling mode. Especially, the changes and different aspects of shear buckling on the boundary between local buckling and global buckling appearin different corrugation shapes. According to the analysis results, interactive buckling mode appeared on the boundary of localbuckling and global bucking in trapezoidal corrugation. However, in the case of corrugated steel plates with sinusoidalconfiguration, interactive buckling mode appeared in the part where global bucking takes place. Besides, trapezoidal shapes are ofadvantages on shear buckling resistance in the local buckling section, and so are sinusoidal shapes in the global buckling section. 본 연구는 정현형 주름과 마름모형 주름 형상의 전단좌굴 특성을 비교, 분석하는 것이 목적이다. 이를 위해서 동일한 길이의 마름모꼴주름과 정현파주름을 해석대상모델로 채택하였으며, 선형좌굴해석을 통한 전단좌굴특성과 이론식에 의한 특성을 분석하였다. 일반적으로주름강판의 전단좌굴 형태는 국부좌굴, 전체좌굴 및 두 좌굴에 의한 연성좌굴로 분류된다. 그러나 마름모꼴주름과는 달리 정현파주름형상은 평평한 면이 없기 때문에 전단좌굴의 양상에 대한 경향이 달라진다. 특히 국부좌굴과 전체좌굴의 경계에서 나타나는 전단응력변화와 양상은 주름형태에 의해 차이가 난다. 분석 결과에서 볼 때, 제형 (마름모꼴)의 경우는 이론식내의 전체좌굴과 국부좌굴의 경계에서 연성좌굴모드가 발생했다. 그러나 정현파형의 경우 전체좌굴이 발생하는 구간에서 연성좌굴모드가 발생하는 양상을 보였다. 또한 국부좌굴 구간에는 제형형상이 그리고 전체좌굴 구간에서는 정현파형상이 전단좌굴에 저항하는데 유리하게 작용하였다.