다중 균열을 갖는 신장 보의 균열 에너지와 지배방정식

손수덕 한국공간구조학회 2024 한국공간구조학회지 Vol.24 No.1

This paper aims to advance our understanding of extensible beams with multiple cracks by presenting a crack energy and motion equation, and mathematically justifying the energy functions of axial and bending deformations caused by cracks. Utilizing an extended form of Hamilton's principle, we derive a normalized governing equation for the motion of the extensible beam, taking into account crack energy. To achieve a closed-form solution of the beam equation, we employ a simple approach that incorporates the crack's patching condition into the eigenvalue problem associated with the linear part of the governing equation. This methodology not only yields a valuable eigenmode function but also significantly enhances our understanding of the dynamics of cracked extensible beams. Furthermore, we derive a governing equation that is an ordinary differential equation concerning time, based on orthogonal eigenmodes. This research lays the foundation for further studies, including experimental validations, applications, and the study of damage estimation and detection in the presence of cracks

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.

실변수 유전자 알고리즘을 이용한 사인형 주름 웨브 보의 최적구조설계

손수덕,이승재,Shon, Su-Deok,Lee, Seung-Jae 한국강구조학회 2011 韓國鋼構造學會 論文集 Vol.23 No.5

스티프너로 보강된 플레이트 거더 대신에 주름 웨브를 사용하는 근본적인 장점은 얇은 판으로 형성된 편평한 웨브에서 발생하는 좌굴에 관한 불안정 문제를 해결할 수 있는 것 뿐 아니라 수직 스티프너의 필요성도 함께 해결 됨으로써 경제적인 장점을 제공받게 된다. 따라서 본 연구에서는 사인형 주름 웨브를 가진 보의 구조설계 기법과 실변수 알고리즘을 이용하여 최적화 문제를 다루도록 한다. 구조설계과정과 설계변수들은 EN 1993-1-5, DASt-R015 및 Pasternak 등(2004)을 통해서 구성하며, 주름 웨브의 전단좌굴에 대한 유효한 설계가능영역에 대해 비교, 고찰한다. 구조설계 최적화를 위해서, 목적함수는 사인형 주름 웨브 보의 중량으로 정의하여 최소중량최적화를 수행하며, 제약조건으로는 세장비, 부재력 저항능력 및 보의 허용처짐에 대해서 고려한다. 최종적으로 등분포 하중의 단순보 모델을 해석 대상으로 채택하며, 유전자 연산에 있어서 효율적인 확률변수에 대해 연구한다. The underlying advantages of using thin-walled corrugatedwebs instead of plate girders with stiffeners are the elimination of instability problems associated with buckling of the thin-walled flat plate, and elimination of the need for transverse stiffeners, which alsoresults in economic advantages. This paper focuses on two aspects related to the structural design technique forsinusoidal corrugated web steel beams, and the optimum design of the beams using real-value genetic algorithms. The structural design process and design variables used in this optimization werecomposed with EN 1993-1-5, DASt-R015 standard and Pasternak et al. (2004), and the valid design capacity of shear buckling of the standards were compared. For the optimum structural design, the objective function, presented as the fullweight of the sinusoidal corrugated web beams, and the slenderness, member forces, and maximum deflection of the beam, were considered constraints. Finally, the simple beam under the uniform load was adopted as a numerical example, and the effective probability parameters of the genetic operators were considered to find the global minimum point.

고충진 압출성형 합성목재를 이용한 모듈러 돔의 구조모델링에 관한 연구

손수덕,곽의신,이승재 한국구조물진단유지관리공학회 2015 한국구조물진단유지관리공학회 논문집 Vol.19 No.2

This paper aims at developing an environmentally friendly modular dome structure system with highly filled extrusion wood-plastic composite (WPC) member, and manufacturing a real-size specimen by modularizing members and nodes. The member used in the model is the WPC member with 70% wooden fiber contests, which is higher then previous WPC one. Its members and nodes are modularized by analyzing geometric characteristics of icosahedral-based geodetic dome. Applicapability of the 6ea prototype nodes and 3ea prototype members to the modular dome is examined with the results of the modulaization and the making process for the real-size specimen. Besides, from the analysis results, the lowest buckling mode is expected to be a nodal buckling on a node near the boundary. 본 연구의 목적은 고충진 합성목재를 이용하여 친환경 모듈러 돔 구조시스템을 개발하고 부재와 절점을 모듈화하여 실제 구조체을 제작하는 것이다. 기존의 합성목재에 비해 높은 70% 목분함량 합성목재를 돔 구조모델의 부재로 이용하였고, 정이십면체 기반 지오데직 돔의기하학적 특성을 분석하여 절점과 부재를 모듈화 하였다. 돔의 제작을 위한 모듈화와 실제 구조물의 제작과정의 연구결과로부터 6가지 절점과 3개의 부재종류의 모듈러 돔에 대한 적용성을 검토할 수 있었다. 또한 해석결과에서 최저차 좌굴모드는 경계부의 절점에서 절점좌굴이 예상되었다.

제형주름강판의 주름깊이에 따른 이력거동과 에너지 소산능력

손수덕,유미나,이승재 대한건축학회 2016 대한건축학회논문집 Vol.32 No.12

Trapezoidal-corrugated steel plate refers to a plate with horizontal and inclined panels that have been processed at a fixed angle. When this plate is used in a shear wall system, rigidity along the corrugation direction does not increase due to its accordion effect. This plate is also economical to use because it serves as a vertical stiffener. However, corrugated steel plates have orthotropic characteristics. It is also not easy to determine the corrugation shape for design because their shear performance or hysteric behavior is difficult to reveal. In this study, the hysteric behavior of a corrugated steel plate under cyclic loading was investigated and the characteristics of the corrugated steel plates of the same size were analyzed according to the corrugation depth. Results of the experiment were compared with the buckling shape through a buckling analysis of the corrugated steel plate, and the collapse mechanism under cyclic loading was examined. In conclusion, the fracture at boundary had an effect on the generation of buckling, and the specimen where shear buckling occurred showed better resistance and cumulative energy dissipation according to corrugation shape than the specimen where no shear buckling occurred.

돔형 스페이스 프레임 구조물의 하중모드에 따른 분기점 특성에 관한 연구

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

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(R_L) 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(R_L), the nodal buckling phenomenon occur at low the ratio of load(R_L), the global buckling occur at high the ratio of load(R_L). In case of the global buckling, the load of bifurcation is about from 50% to 70% of perfect one's snap-through load. 스페이스 프레임 구조물은 연속체 쉘 구조물의 원리를 이용하여 매우 넓은 공간을 효과적으로 덮을 수 있는 구조물이지만 뜀좌굴 및 분기좌굴 등과 같은 불안정거동은 돔형 구조물에서는 더욱 복잡하게 나타난다. 또한 붕괴메커니즘의 이론적 연구와 실험적 연구 결과들 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(R_L)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 R_L에서 절점좌굴이, 높은 R_L에서는 전체좌굴이 지배적이고, 전체좌굴이 나타나는 경우, 분기좌굴하중은 완전형상의 극한점좌굴하중의 약 50%에서 70%의 분포를 보였다.

공간구조물의 비선형해석과 불안정현상

손수덕,Shon, Su-Deok 한국공간구조학회 2004 한국공간구조학회지 Vol.4 No.3

돔형 스페이스 프레임의 부재강성변화에 따른 임계좌굴하중과 유효좌굴길이계수

손수덕,이승재,Shon, Su-Deok,Lee, Seung-Jae 한국공간구조학회 2013 한국공간구조학회지 Vol.13 No.1

This study investigated characteristics of buckling load and effective buckling length by member rigidity of dome-typed space frame which was sensitive to initial conditions. A critical point and a buckling load were computed by analyzing the eigenvalues and determinants of the tangential stiffness matrix. The hexagonal pyramid model and star dome were selected for the case study in order to examine the nodal buckling and member buckling in accordance with member rigidity. From the numerical results, an effective buckling length factor of adopted models was bigger than that of Euler buckling for the case of fixed boundary. These numerical models indicated that the influence of nodal buckling was greater than that of member buckling as member rigidity was higher. Besides, there was a tendency that the bifurcation appeared on the equilibrium path before limit point in the member buckling model.

스텝 하중을 받는 3-자유절점 공간 트러스 모델의 동적 좌굴 특성

손수덕,황경주 한국공간구조학회 2020 한국공간구조학회지 Vol.20 No.2

In this paper, the dynamic snapping of the 3-free-nodes spatial truss model was studied. A governing equation was derived considering geometric nonlinearity, and a model with various conditions was analyzed using the fourth order Runge-Kutta method. The dynamic buckling phenomenon was observed in consideration of sensitive changes to the force mode and the initial condition. In addition, the critical load level was analyzed. According to the results of the study, the level of critical buckling load elevated when the shape parameter was high. Parallelly, the same result was caused by the damping term. The sensitive asymmetrical changes showed complex orbits in the phase space, and the critical load level was also becoming lowly. In addition, as the value of damping constant was high, the level of critical load also increases. In particular, the larger the damping constant, the faster it converges to the equilibrium point, and the occurrence of snapping was suppressed.

비대칭 초기 조건을 갖는 얕은 아치의 동적 불안정과 순시 주파수 변화

손수덕,하준홍 한국공간구조학회 2020 한국공간구조학회지 Vol.20 No.2

This paper examined the dynamic instability of a shallow arch according to the response characteristics when nearing critical loads. The frequency changing feathers of the time-domain increasing the loads are analyzed using Fast Fourier Transformation (FFT), while the response signal around the critical loads are analyzed using Hilbert-Huang Transformation (HHT). This study reveals that the models with an arch shape of h = 3 or higher exhibit buckling, which is very sensitive to the asymmetric initial conditions. Also, the critical buckling load increases as the shape increases, with its feather varying depending on the asymmetric initial conditions. Decomposition results show the decrease in predominant frequency before the threshold as the load increases, and the predominant period doubles at the critical level. In the vicinity of the critical level, sections rapidly manifest the displacement increase, with the changes in Instantaneous Frequency (IF) and Instant Energy (IE) becoming apparent.