비선형 유한요소해석 프로그램을 이용한 차체 구조물의 동강성 및 정강성 해석

김성현(Sunghyun Kim),김형일(Hyungil Kim),변형배(Hyungbai Byun),김동석(Dongseok Kim),이용훈(Yonghoon Lee),김일환(Ilhwan Kim),허승진(Seung Jin Heo),임홍재(Hong Jae Yim) 한국자동차공학회 2011 한국자동차공학회 부문종합 학술대회 Vol.2011 No.5

In this study, dynamic stiffness analysis and static stiffness analysis were conducted by using nonlinear finite element analysis program and linear finite element analysis respectively to compare the results and to confirm reliability about results of nonlinear finite element analysis program. First, dynamic stiffness analysis has been performed on side out panel, crash box, sub-frame and BIW(Body In White) that has been connected with front bumper, rear bumper and sub-frame. Second, static stiffness analysis has been conducted on crash box and hood that has been modeled with spot weld elements and rigid body elements. Consequently, differences of dynamic and static stiffness analysis results through nonlinear finite element analysis program and linear finite element analysis were below 6 % but difference was more than 6 % as to dynamic stiffness of BIW.

Nonlinear numerical analyses of a pile-soil system under sinusoidal bedrock loadings verifying centrifuge model test results

Kim, Yong-Seok,Choi, Jung-In Techno-Press 2017 Geomechanics & engineering Vol.12 No.2

Various centrifuge model tests on the pile foundations were performed to investigate fundamental characteristics of a pile-soil-foundation system recently, but it is hard to find numerical analysis results of a pile foundation system considering the nonlinear behavior of soil layers due to the dynamic excitations. Numerical analyses for a pile-soil system were carried out to verify the experimental results of centrifuge model tests. Centrifuge model tests were performed at the laboratory applying 1.5 Hz sinusoidal base input motions, and nonlinear numerical analyses were performed utilizing a finite element program of P3DASS in the frequency domain and applying the same input motions with the intensities of 0.05 g~0.38 g. Nonlinear soil properties of soil elements were defined by Ramberg-Osgood soil model for the nonlinear dynamic analyses. Nonlinear numerical analyses with the P3DASS program were helpful to predict the trend of experimental responses of a centrifuge model efficiently, even though there were some difficulties in processing analytical results and to find out unintended deficits in measured experimental data. Also nonlinear soil properties of elements in the system can be estimated adequately using an analytical program to compare them with experimental results.

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>

전통목구조해석의 문제점 분석과 개선방안

정성진(Jung, Sung-Jin) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.10

In structure design practical fields, computer programs like MIDAS and SAP2000 etc. are widely used for the evaluation of the structural performance of the Korean traditional wood structures. It is necessary to use a reasonable analysis model and method for the evaluation of the structural performance. Considering the structural characteristics of the Korean traditional wood structures, it is appropriate to analyze lower frame composed of beam-columns and upper frame which is a roof structure separately. Especially, in the analysis including lateral loads like seismic or wind load etc., it seems to be reasonable to analyze lower frame with an assumption of roof frame as a rigid diaphragm. Because connections between columns and beams have very small rotational stiffness, lower frame may be unstable. So, in the structure design practical fields, connections are modelled by using various assumptions and linear analysis is performed mainly. However, irrationality may be included in these assumptions and analysis method unfortunately. Therefore, in this study, problems in the analysis models and methods for the Korean traditional wood structures, used in structure design practical fields, are investigated first, then some improvement plans are proposed on the basis of investigation results. Because the Korean traditional wood structures may have no high lever stabilities, it is necessary to perform geometric nonlinear analysis. So, geometric nonlinear analysis method including P-δ effect is studied.

탄소성강성특성을 갖는 압축전담 및 인장전담 요소에 관한 연구

정성진(Jung Sung-Jin) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.7

It is necessary to use a compression only elements(CO elements) or tension only elements(TO elements) in the structural analysis. Especially, in the case of the structural analysis for Korean traditional wood structures, connections must be modelled by CO or TO elements. In the case of the structural analysis of the culvert structures, CO elements must be used, with the consideration of buoyancy effect. Most commercial computer programs such as SAP2000 and MIDAS/GEN provide these elements. However, since these computer programs only present the concept and the way of using the commands according to respective programs, the basic theories and programming methods can not be understood. Therefore, it is necessary to establish the basic theories and the programming techniques to consider CO elements or TO elements. This study presents the concept and the programming method considering CO elements or TO elements with elasto-plastic stiffness properties, which are the most general nonlinear cases. Basic theories for the consideration of CO elements or TO elements are studied first, where some of possible methods to develop a computer program are investigated. On the basis of these theoretical backgrounds, the most reasonable method and an available algorithm is derived, and then a computer program(sNs) is developed based on the theory and algorithm studied. Lastly, a sample analysis is performed to verify the possibility of the application of sNs.

Inelastic vector finite element analysis of RC shells

Min, Chang-Shik,Gupta, Ajaya Kumar Techno-Press 1996 Structural Engineering and Mechanics, An Int'l Jou Vol.4 No.2

Vector algorithms and the relative importance of the four basic modules (computation of element stiffness matrices, assembly of the global stiffness matrix, solution of the system of linear simultaneous equations, and calculation of stresses and strains) of a finite element computer program for inelastic analysis of reinforced concrete shells are presented. Performance of the vector program is compared with a scalar program. For a cooling tower problem, the speedup factor from the scalar to the vector program is 34 for the element stiffness matrices calculation, 25.3 for the assembly of global stiffness matrix, 27.5 for the equation solver, and 37.8 for stresses, strains and nodal forces computations on a Gray Y-MP. The overall speedup factor is 30.9. When the equation solver alone is vectorized, which is computationally the most intensive part of a finite element program, a speedup factor of only 1.9 is achieved. When the rest of the program is also vectorized, a large additional speedup factor of 15.9 is attained. Therefore, it is very important that all the modules in a nonlinear program are vectorized to gain the full potential of the supercomputers. The vector finite element computer program for inelastic analysis of RC shells with layered elements developed in the present study enabled us to perform mesh convergence studies. The vector program can be used for studying the ultimate behavior of RC shells and used as a design tool.

단일곡률을 갖는 벽요소의 강성행렬식

정성진(Jung Sung-Jin),문정호(Moon Jeong-Ho) 대한건축학회 2007 大韓建築學會論文集 : 構造系 Vol.23 No.11

The importance of nonlinear analysis for building structures is more and more increasing recently. In the case of the nonlinear analysis for the shear wall structure system, a macro analytic model with axial spring, shear spring, and bending spring has been used due to economical efficiency and time saving. Although some macro analytic models for shear wall structure are implemented in some computer programs like ETABS, SAP2000, MIDAS, neoMAX-3D, these models are restricted to shallow walls because they have double curvatures. In this study, a method for the transformation of member forces into nodal loads is suggested, and a stiffness matrix based on this transformation method is presented for the analysis of shear wall structure. The stiffness matrix presented in this paper is about a macro analytic model with single curvature. A finite element analysis is performed for the verification of the wall element presented in this paper. Lastly, the results of finite element analysis are compared with theoretical solution and the analysis results using RAM, SAP2000, MIDAS, and neoMAX-3D programs.

이선형 재료모델의 비선형 정적해석을 위한 강성추정 알고리즘 개발

정성진(Jung, Sung-Jin),박세희(Park, Sei-He) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.2

구조물의 비선형 지진응답을 평가하는 것은 내진공학에 있어서 중요한 요소로 인식되고 있다. 비선형 정적해석은 이를 위한 대표적인 방법론의 하나이며, 특정 해석단계에서의 구조물 강성추정을 위한 다양한 수치해석적 방법론들이 제시, 적용되고 있다. 하지만, 이러한 방법론들은 상당한 해석시간을 요하거나 부정확한 간편법에 그치고 있어 실무적용에 많은 어려움이 존재한다. 이러한 이유로 본 연구에서는 비선형 정적해석 시 정확하고 효과적인 구조물 강성추정 방법론을 제시하 고자 한다. 이를 위하여, 기존의 단계해석법에 대한 이론적 연구를 수행하였으며, 이를 바탕으로 이선형 재료모델 특성을 가진 구조물의 강성구성 알고리즘을 제시하였다. 최종적으로, 제시된 알고리즘을 적용한 컴퓨터 프로그램 sNs를 개발하였다. Estimating the nonlinear seismic response of structure in earthquake engineering is important. Nonlinear static analysis is a typical method, and a variety of methods and techniques for estimating the stiffness of structural system at a certain analysis stage have been introduced and used in numerical structural analysis. On the other hand, such methods have many difficulties in practical usage because they use time-consuming iterative methods or simplified algorithms for calculating the structural stiffness at specific points in the time of nonlinear static analysis. For this reason, this study suggests an accurate and effective method for estimating the stiffness of a structure in nonlinear static analysis. For this goal, existing theories of an incremental step-by-step solution was investigated first. Subsequently, an algorithm available for calculating the precise stiffness of a structural system, each element of which has a bilinear material model, was developed based on the investigated methods. Finally, a computer program, sNs, was developed with the algorithm used.

접촉면 요소를 사용한 합성 지하벽의 비선형 해석

서수연,이성호 한국구조물진단유지관리공학회 2007 한국구조물진단유지관리공학회 논문집 Vol.11 No.3

본 연구의 목적은 H-Pile과 벽체가 합성하여 거동하는 합성 지하벽의 내력 및 구조적 거동을 해석적으로 파악하고 구조성능을 평가하여 다양한 형태의 응력조건에 대한 거동예측 방법을 제시하는 것이다. 이를 위하여 유한요소 범용 프로그램인 ATENA를 이용하여 H-Pile, 콘크리트 벽체, 스터드볼트 연결부 등에 대한 모델링방법을 설정하고 기 실험된 합성지하벽 실험체들에 대한 비선형 해석을 실시하였다. H-Pile과 콘크리트 벽체를 연결하는 스터드볼트에 의해 전달되는 전단 및 축응력을 접촉면 요소로 모델링하여 비선형 해석을 실시한 결과, 비록 초기강성은 해석결과가 다소 높게 나타났지만, 실험결과와 해석결과가 좋은 대응을 보이는 것으로 나타났다. The objective of this paper is to suggest a nonlinear analysis process to predict the structural behavior and strength of composite basement wall member combined with H-Pile. Therefore, the structural behavior of composite basement wall is studied and the special nonlinear characteristics of each elements such as H-Pile, concrete wall, and shear connectors are idealized using ATENA program. Finally, the result is compared with previous test result. Research result shows that there is a good co-relation between analysis and test results even if analysis result has little bit higher initial stiffness than test result. It can be concluded that the nonlinear behavior of composite basement wall is suitably predicted by using the contact element model in ATENA program as shear connector element.

Parameter estimation of four-parameter viscoelastic Burger model by inverse analysis: case studies of four oil-refineries

Dey, Arindam,Basudhar, Prabir Kr. Techno-Press 2012 Interaction and multiscale mechanics Vol.5 No.3

This paper reports the development of a generalized inverse analysis formulation for the parameter estimation of four-parameter Burger model. The analysis is carried out by formulating the problem as a mathematical programming formulation in terms of identification of the design vector, the objective function and the design constraints. Thereafter, the formulated constrained nonlinear multivariable problem is solved with the aid of fmincon: an in-built constrained optimization solver module available in MatLab. In order to gain experience, a synthetic case-study is considered wherein key issues such as the determination and setting up of variable bounds, global optimality of the solution and minimum number of data-points required for prediction of parameters is addressed. The results reveal that the developed technique is quite efficient in predicting the model parameters. The best result is obtained when the design variables are subjected to a lower bound without any upper bound. Global optimality of the solution is achieved using the developed technique. A minimum of 4-5 randomly selected data-points are required to achieve the optimal solution. The above technique has also been adopted for real-time settlement of four oil refineries with encouraging results.