A simplified geometric stiffness in stability analysis of thin-walled structures by the finite element method

Senjanovic, Ivo,Vladimir, Nikola,Cho, Dae-Seung The Society of Naval Architects of Korea 2012 International Journal of Naval Architecture and Oc Vol.4 No.3

Vibration analysis of a thin-walled structure can be performed with a consistent mass matrix determined by the shape functions of all degrees of freedom (d.o.f.) used for construction of conventional stiffness matrix, or with a lumped mass matrix. In similar way stability of a structure can be analysed with consistent geometric stiffness matrix or geometric stiffness matrix with lumped buckling load, related only to the rotational d.o.f. Recently, the simplified mass matrix is constructed employing shape functions of in-plane displacements for plate deflection. In this paper the same approach is used for construction of simplified geometric stiffness matrix. Beam element, and triangular and rectangular plate element are considered. Application of the new geometric stiffness is illustrated in the case of simply supported beam and square plate. The same problems are solved with consistent and lumped geometric stiffness matrix, and the obtained results are compared with the analytical solution. Also, a combination of simplified and lumped geometric stiffness matrix is analysed in order to increase accuracy of stability analysis.

A simplified geometric stiffness in stability analysis of thin-walled structures by the finite element method

Ivo Senjanović,Nikola Vladimir,조대승 대한조선학회 2012 International Journal of Naval Architecture and Oc Vol.4 No.3

Vibration analysis of a thin-walled structure can be performed with a consistent mass matrix determined by the shape functions of all degrees of freedom (d.o.f.) used for construction of conventional stiffness matrix, or with a lumped mass matrix. In similar way stability of a structure can be analysed with consistent geometric stiffness matrix or geometric stiffness matrix with lumped buckling load, related only to the rotational d.o.f. Recently, the simplified mass matrix is constructed employing shape functions of in-plane displacements for plate deflection. In this paper the same approach is used for construction of simplified geometric stiffness matrix. Beam element, and triangular and rectangular plate element are considered. Application of the new geometric stiffness is illustrated in the case of simply supported beam and square plate. The same problems are solved with consistent and lumped geometric stiffness matrix,and the obtained results are compared with the analytical solution. Also, a combination of simplified and lumped geometric stiffness matrix is analysed in order to increase accuracy of stability analysis.

대학생의 도형심리 유형, 긍정심리자본, 의사소통능력 간의 경로분석

김명숙(Myoung-Sook Kim),서호찬(Ho-Chan SEO) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.6

본 연구의 목적은 대학생들의 의사소통능력을 향상시키기 위한 프로그램을 개발하기 위한 기초연구로서 도형심리유형과 의사소통능력과의 관계에서 긍정심리자본이 매개할 수 있는지 확인해보는 것이다. 이를 위해 전국의 대학생들 321명을 대상으로 설문조사하였으며 척도의 신뢰도분석, 회귀분석, 경로분석으로 자료를 분석하였다. 회귀분석을 통해 도형심리유형, 긍정심리자본, 의사소통능력의 변수들이 서로 긍정적인 회귀결과로 나타났다. 경로분석을 통해 도형심리 유형과 의사소통능력과의 관계에서 긍정심리자본이 매개역할을 하는 것을 확인하였으며 그 결과는 도형심리의 각 유형에 따라 다른 양상을 보였다. 동그라미 유형은 의사소통능력에 대하여 긍정심리자본의 하위인 복원력을 매개하거나 직접적으로 영향을 미치고 있으며 세모 유형은 의사소통능력에 대하여 긍정심리자본의 하위요인인 자기효능감과 복원력을 매개해 영향을 미치는 것으로 나타났다. 네모 유형은 의사소통능력에 대하여 긍정심리자본의 하위요인인 자기효능감을 매개하거나 직접적으로 영향을 미치고 있으며 에스 유형은 의사소통능력에 대하여 긍정심리자본을 매개하지 않고 직접적으로만 영향을 미치는 것으로 나타났다. 따라서 대학생들을 위한 의사소통향상프로그램을 개발하기 위해서는 위와 같은 결과를 고려하여 도형심리유형별로 긍정심리자본이 적용된 프로그램을 개발할 수 있을 것이다. The objective of this study is to conduct basic research for the development of programs for improving university students" communication competence. As such, it seeks to determine if positive psychological capital can mediate the relationship between the geometric psychology type and communication competence. To that end, 321 Korean university students were surveyed using a questionnaire, and the data underwent scale reliability analysis, regression analysis, and path analysis. Regression analysis revealed the consistent regression results of variables, including geometric psychology type, positive psychological capital, and communication competence. Path analysis confirmed that positive psychological capital mediated the relationship between the geometric psychology type and communication competence, and the results suggested different patterns according to type of geometric psychology. The circle type mediated the sub-variable resilience vis-a-vis communication competence, and directly influenced the latter. The triangle type mediated the sub-factors of positive psychological capital - self-efficacy and resilience - vis-a-vis communication competence, and thus influencing the latter. The square type mediated the sub-factor of positive psychological capital - self-efficacy - vis-a-vis communication competence, and directly influenced the latter. The S type did not mediate positive psychological capital vis-a-vis communication competence, but directly influenced the latter. Thus, considering the above findings, in order to develop university students communication improvement programs, programs should be developed with the application of positive psychological capital considering geometric psychology type.

사장교의 기하학적 비선형 거동의 해석적 연구

김승준(Kim Seungjun),이기세(Lee Kee Sei),김경식(Kim Kyung Sik),강영종(Kang Young Jong) 대한토목학회 2010 대한토목학회논문집 A Vol.30 No.1A

본 연구에서는 사장교의 기하학적 비선형 거동을 기하학적 비선형 유한요소 해석을 통해 분석한다. 사장교의 주탑 및 거더는 휨 모멘트 뿐만 아니라 케이블의 장력에 의해 축력이 작용한다. 즉 거더와 주탑은 보-기둥 부재와 같이 휨모멘트와 축력의 상호작용에 의한 대변위 거동을 일으킬 수 있다. 본 연구에서는 기하학적 비선형 해석을 통해 완성계 사장교의 대변위 효과 주탑 및 거더의 보-기둥 효과 그리고 케이블의 새그효과가 모두 고려된 비선형 거동을 검토하였다. 거더 및 주탑은 6자유도 프레임 요소로 모사하고 사장교 케이블은 새그효과를 효율적으로 고려하기 위해 3지유도 등가 트러스 요소를 사용하여 모사하였다. 해석은 먼저 사하중에 대한 초기 형상 해석을 통해 사하중을 고려하고 이 후 각기 다른 형태의 활하중에 대한 기하학적 비선형 해석을 수행하였다. 해석 후 각 모델의 변형형상, 각 주요 지점의 하중-변위곡선 케이블 장력의 변화등의 정량적 수치를 분석하여 고려한 활하중 형태 및 사장교 형식에 대한 주요 기하학적 비선형 거동을 규명하였다. This paper presents an investigation on the geometric nonlinear behavior of cable-stayed bridges using geometric nonlinear finite element analysis method. The girder and mast in cable-stayed bridges show the combined axial load and bending moment interaction due to horizontal and vertical forces of inclined cable. So these members are considered as beam-column member. In this study, the nonlinear finite element analysis method is used to resolve the geometric nonlinear behavior of cable-stayed bridges in consideration of beam-column effect, large displacement effect (known as P-δ effect) and cable sag effect. To analyze a cable-stayed bridge model, nonlinear 6-degree of freedom frame element and nonlinear 3-degree of free-dom equivalent truss element is used. To resolve the geometric nonlinear behavior for various live load cases, the initial shape analysis is performed for considering dead load before live load analysis. Then the geometric nonlinear analysis for each live load case is performed. The deformed shapes of each model, load-displacement curves of each point and load-tensile force curves for each cable are presented for quantitative study of geometric nonlinear behavior of cable-stayed bridges.

Geometrically nonlinear transient analysis of composite laminated plate and shells subjected to low-velocity impact

Elsevier 2016 Composite structures Vol.142 No.-

<P><B>Abstract</B></P> <P>In this study, the transient responses of a composite laminated plate and cylindrical shells subjected to low-velocity impacts were investigated numerically. The shear deformation theory of a doubly curved shell and von Karman’s large deflection theory were used to develop a geometrically nonlinear finite element program. It is well-known that in the case of a flat plate with fixed boundary edges, a geometrically nonlinear analysis yields larger contact forces and smaller deflections than a corresponding linear analysis. However, in the case of cylindrical shells, an opposite result was found in this study; a geometrically nonlinear analysis exhibited smaller contact forces and larger deflections than a corresponding linear analysis. The reason for this opposite result is described in this study. Conversely, with a plate and shells that have the same size, shells with a larger curvature exhibited smaller deflections and larger contact forces. The strain distribution at the bottom surface of the plate/shells using the geometrically nonlinear analysis exhibited markedly or only marginally larger tensile areas than those produced using the linear analysis.</P>

코일 스프링 설계인자의 내구 성능 영향 분석

전정일(Jeongil Jeon),장의선(Euisun Jang),유영일(Youngil Ryu) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

In the past, many prototypes of coil spring have been necessary to find out the optimal design parameters for good performances in stiffness, NVH, durability and etc. However, these days, many design variants of spring can be evaluated before manufacturing stage due to engineering software which can simulate the nonlinear characteristics of spring motion. In this paper the effect of design parameters affecting the durability performance is analyzed using CAE(Computer Aided Engineering). The stress time history was obtained by means of geometric nonlinear analysis considering large deformation and contact of a spring and then the fatigue analysis was performed. A test for measuring strain was performed to verity the reliability of the finite element model for geometric nonlinear analysis, and the fatigue test was done for validation of fatigue analysis. As the result of these simulations, appropriate design parameters for improving durability performance of a coil spring were proposed.

An application of large displacement limit analysis to frame structures

Noel Challamel 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.2

The aim of this paper is to give a rigorous framework for the interpretation of limit analysis results including large displacements. The presentation is oriented towards unidimensional media (beams) but two-dimensional (plates) or three-dimensional media are also concerned. A single-degree-of-freedom system is first considered: it shows the basic phenomena of large displacement limit analysis or secondorder limit analysis. The results are compared to those of a continuous system and the differences between both systems are discussed. Theoretical results are obtained using the kinematical approach of limit analysis. An admissible load-displacement plane is then defined, according to the yield design theory. The methodology used is applied to frame structures. The presented results are nevertheless different from those already published in the literature, as the virtual displacement field can be distinguished from the displacement field at collapse. The simplicity of large displacement limit analysis makes it attractive for practical engineering applications. The load-displacement upper bound can be used for instance in the optimal design of steel frames in seismic areas.

사장교의 최적 초기형상 및 무응력길이 결정을 위한 간략해석법

정명락,박세웅,민동주,김문영 대한토목학회 2016 대한토목학회논문집 Vol.36 No.6

A simplified analysis method is first proposed in order to determine an optimized initial shape of cable-stayed bridges including all unstrained element lengths without using complicated nonlinear FE analysis. The unstrained-length based FE method is thenpresented using the unstrained lengths by the simplified analysis. To demonstrate validity and accuracy of the proposed method, Incheon bridge model having the fabrication camber is constructed and initial shaping analysis is performed using the presented method and commercial finite element analysis program, MIDAS. Resultantly it is shown that the initial solutions by the proposed algorithm are well optimized and in good agreement with those by MIDAS except for axial displacements of the main member. 고정하중을 받는 사장교의 최적 초기형상 결정을 위한 간략해석법을 제시한다. 이 방법은 비선형 유한요소 해석을 수행하지 않고 최적의 초기형상을 구현할 수 있으며, 최소의 휨모멘트를 발생시키는 무응력길이를 제공한다. 초기형상 해석 후 여타의 하중조합 또는 시공단계해석을 수행하기 위해 무응력길이를 변화시키지 않고 Newton-Raphson 반복법을 수행하는 무응력길이법을 이용한다. 수치예제는 제작캠버를 포함한 인천대교 2차원 모델이며, 제시된 해석법과 상용 유한요소해석 프로그램 MIDAS의 초기형상 해석결과를 비교·분석한다. 주로 케이블의 장력과 주부재의 휨모멘트 및 변위를 관찰하였으며, 두 해석결과는 축방향 변위를 제외하고 모든 결과 값이 서로 잘 일치함을 확인할 수 있었다.

An application of large displacement limit analysis to frame structures

Challamel, Noel Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.2

The aim of this paper is to give a rigorous framework for the interpretation of limit analysis results including large displacements. The presentation is oriented towards unidimensional media (beams) but two-dimensional (plates) or three-dimensional media are also concerned. A single-degree-of-freedom system is first considered: it shows the basic phenomena of large displacement limit analysis or second-order limit analysis. The results are compared to those of a continuous system and the differences between both systems are discussed. Theoretical results are obtained using the kinematical approach of limit analysis. An admissible load-displacement plane is then defined, according to the yield design theory. The methodology used is applied to frame structures. The presented results are nevertheless different from those already published in the literature, as the virtual displacement field can be distinguished from the displacement field at collapse. The simplicity of large displacement limit analysis makes it attractive for practical engineering applications. The load-displacement upper bound can be used for instance in the optimal design of steel frames in seismic areas.

Finite Element Modeling and Nonlinear Analysis for Seismic Assessment of Off-Diagonal Steel Braced RC Frame

Keyvan Ramin,Mitra Fereidoonfar 한국콘크리트학회 2015 International Journal of Concrete Structures and M Vol.9 No.1

The geometric nonlinearity of off-diagonal bracing system (ODBS) could be a complementary system to covering and extending the nonlinearity of reinforced concrete material. Finite element modeling is performed for flexural frame, x-braced frame and the ODBS braced frame system at the initial phase. Then the different models are investigated along various analyses. According to the experimental results of flexural and x-braced frame, the verification is done. Analytical assessments are performed in according to three dimensional finite element modeling. Nonlinear static analysis is considered to obtain performance level and seismic behaviour, and then the response modification factors calculated from each model’s pushover curve. In the next phase, the evaluation of cracks observed in the finite element models, especially for RC members of all three systems is performed. The finite element assessment is performed on engendered cracks in ODBS braced frame for various time steps. The nonlinear dynamic time history analysis accomplished in different stories models for three records of Elcentro, Naghan and Tabas earthquake accelerograms. Dynamic analysis is performed after scaling accelerogram on each type of flexural frame, x-braced frame and ODBS braced frame one by one. The base-point on RC frame is considered to investigate proportional displacement under each record. Hysteresis curves are assessed along continuing this study. The equivalent viscous damping for ODBS system is estimated in according to references. Results in each section show the ODBS system has an acceptable seismic behaviour and their conclusions have been converged when the ODBS system is utilized in reinforced concrete frame.