• Title, Summary, Keyword: Nonlinear Analysis

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Analysis of Nonlinear Resistive Networks (비선형저항(resistive)회로망의 해석)

  • Kyun Hyon Tchah
    • 전기의세계
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    • v.23 no.3
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    • pp.70-76
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    • 1974
  • Computer is used to analyze nonlinear networks. Integrated circuits and new nonlinear elements have generated much interest in nonlinear circuit theory. A key to the understanding and analysis of nonlinear circuits is the study of characteristics for nonlinear elements and nonlinear resistive networks both in theory and in computation. In this apper, an iteration method using cut set analysis for nonlinear dc analysis based on Branin's method is described. Application of this algorithm to solve two nonlinear problems, is presented and a possible method of improving the basic algorithm by means of a sparse matrix technique is described.

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Effects of damping ratio on dynamic increase factor in progressive collapse

  • Mashhadi, Javad;Saffari, Hamed
    • Steel and Composite Structures
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    • v.22 no.3
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    • pp.677-690
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    • 2016
  • In this paper, the effect of damping ratio on nonlinear dynamic analysis response and dynamic increase factor (DIF) in nonlinear static analysis of structures against column removal are investigated and a modified empirical DIF is presented. To this end, series of low and mid-rise moment frame structures with different span lengths and number of storeys are designed and the effect of damping ratio in DIF is investigated, performing several nonlinear static and dynamic analyses. For each damping ratio, a nonlinear dynamic analysis and a step by step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived. The results of the analysis reveal that DIF is decreased with increasing damping ratio. Finally, an empirical formula is recommended that relates to damping ratio. Therefore, the new modified DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of moment frame buildings with different damping ratios.

Nonlinear finite element analysis of reinforced concrete structures subjected to transient thermal loads

  • Zhou, C.E.;Vecchio, F.J.
    • Computers and Concrete
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    • v.2 no.6
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    • pp.455-479
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    • 2005
  • This paper describes a 2D nonlinear finite element analysis (NLFEA) platform that combines heat flow analysis with realistic analysis of cracked reinforced concrete structures. The behavior models included in the structural analysis are mainly based on the Modified Compression Field Theory and the Distributed Stress Field Model. The heat flow analysis takes into account time-varying thermal loads and temperature-dependent material properties. The capability of 2D nonlinear transient thermal analysis is then implemented into a nonlinear finite element analysis program VecTor2(C) for 2D reinforced concrete membranes. Analyses of four numerical examples are performed using VecTor2, and results obtained indicate that the suggested nonlinear finite element analysis procedure is capable of modeling the complete response of a concrete structure to thermal and mechanical loads.

Case Studies of Nonlinear Response Structural Optimization Using Equivalent Loads (등가하중법을 이용한 비선형 반응 구조최적설계 사례연구)

  • Kim, Yong-Il;Park, Gyung-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.31 no.11
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    • pp.1059-1068
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    • 2007
  • Nonlinear response structural optimization is performed using equivalent loads (NROEL). Nonlinear response optimization is extremely cost because many nonlinear analyses are required. In NROEL, the external loads are transformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response field of linear analysis as that of nonlinear analysis. The primitive from of theory has been published. In this research, the theory is investigated with large scale example problems. Four examples are solved by using NROEL. Conventional optimization with sensitivity analysis using the finite difference method (FDM) is also applied to the same examples. Moreover, response surface optimization method is applied to the last two examples. The results of the optimizations are compared. In nonlinear response optimization of large scale problems, hundreds (or even thousands) of nonlinear analyses are expected to satisfy the convergence criteria. However, in nonlinear response optimization using equivalent loads, only tens of nonlinear analyses are required. The results are discussed and the usefulness of NROEL is presented.

Detection of nonlinear structural behavior using time-frequency and multivariate analysis

  • Prawin, J.;Rao, A. Rama Mohan
    • Smart Structures and Systems
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    • v.22 no.6
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    • pp.711-725
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    • 2018
  • Most of the practical engineering structures exhibit nonlinearity due to nonlinear dynamic characteristics of structural joints, nonlinear boundary conditions and nonlinear material properties. Hence, it is highly desirable to detect and characterize the nonlinearity present in the system in order to assess the true behaviour of the structural system. Further, these identified nonlinear features can be effectively used for damage diagnosis during structural health monitoring. In this paper, we focus on the detection of the nonlinearity present in the system by confining our discussion to only a few selective time-frequency analysis and multivariate analysis based techniques. Both damage induced nonlinearity and inherent structural nonlinearity in healthy systems are considered. The strengths and weakness of various techniques for nonlinear detection are investigated through numerically simulated two different classes of nonlinear problems. These numerical results are complemented with the experimental data to demonstrate its suitability to the practical problems.

Effects of Nonlinear Soil Characteristics on the Dynamic Stiffnesses of a Foundation-Soil System Excited with the Horizontal Motion (비선형 지반특성이 수평 방향운동을 받는 기초지반체계의 동적강성에 미치는 영향)

  • 김용석
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.120-129
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    • 2000
  • As structure-soil interaction analysis for the seismic analysis of structures requires a nonlinear analysis of a structure-soil system considering the inelastic characteristics of soil layers nonlinear analyses of the foundation-soil system with the horizontal excitation were performed considering the nonlinear soil conditions for the nonlinear seismic analysis of structures. Stiff soil profile of SD and soft soil profile of SE specified in UBC were considered for the soil layers of a foundation and Ramberg-Osgood model was assumed for the nonlinear characteristics of soil layers. Studies on the changes of dynamci stiffnesses and damping rations of surface and embedded foundations depending on foundation size soil layer depth and piles were performed to investigate the effects of the nonlinear soil layer on the horizontal and rotational dynamic stiffnesses and damping ratios of the foundation-soil system According to the study results nonlinear prperties of a soil laryer decreeased horizontal and rotational linear stiffnesses and increased damping ratios largely Effects of foundation size soil layer depth and piles were also significant suggesting the necessity of nonlinear seismic analyses of structures.

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Geometrically nonlinear analysis of plane frames composed of flexibly connected members

  • Gorgun, H.
    • Structural Engineering and Mechanics
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    • v.45 no.3
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    • pp.277-309
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    • 2013
  • Beam-to-column connections behaviour plays an important role in the analysis and design of steel and precast concrete structures. The paper presents a computer-based method for geometrically nonlinear frames with semi-rigid beam-to-column connections. The analytical procedure employs modified stability functions to model the effect of axial force on the stiffness of members. The member modified stiffness matrix, and the modified fixed end forces for various loads were found. The linear and nonlinear analyses were applied for two planar steel structures. The method is readily implemented on a computer using matrix structural analysis techniques and is applicable for the efficient nonlinear analysis of frameworks.

Nonlinear interaction analysis of infilled frame-foundation beam-homogeneous soil system

  • Hora, M.S.
    • Coupled systems mechanics
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    • v.3 no.3
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    • pp.267-289
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    • 2014
  • A proper physical modeling of infilled building frame-foundation beam-soil mass interaction system is needed to predict more realistic and accurate structural behavior under static vertical loading. This is achieved via finite element method considering the superstructure, foundation and soil mass as a single integral compatible structural unit. The physical modelling is achieved via use of finite element method, which requires the use of variety of isoparametric elements with different degrees of freedom. The unbounded domain of the soil mass has been discretized with coupled finite-infinite elements to achieve computational economy. The nonlinearity of soil mass plays an important role in the redistribution of forces in the superstructure. The nonlinear behaviour of the soil mass is modeled using hyperbolic model. The incremental-iterative nonlinear solution algorithm has been adopted for carrying out the nonlinear elastic interaction analysis of a two-bay two-storey infilled building frame. The frame and the infill have been considered to behave in linear elastic manner, whereas the subsoil in nonlinear elastic manner. In this paper, the computational methodology adopted for nonlinear soil-structure interaction analysis of infilled frame-foundation-soil system has been presented.

Nonlinear analysis of fibre-reinforced plastic poles

  • Lin, Z.M.;Polyzois, D.;Shah, A.
    • Structural Engineering and Mechanics
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    • v.6 no.7
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    • pp.785-800
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    • 1998
  • This paper deals with the nonlinear finite element analysis of fibre-reinforced plastic poles. Based on the principle of stationary potential energy and Novozhilov's derivations of nonlinear strains, the formulations for the geometric nonlinear analysis of general shells are derived. The formulations are applied to the fibre-reinforced plastic poles which are treated as conical shells. A semi-analytical finite element model based on the theory of shell of revolution is developed. Several aspects of the implementation of the geometric nonlinear analysis are discussed. Examples are presented to show the applicability of the nonlinear analysis to the post-buckling and large deformation of fibre-reinforced plastic poles.

Nonlinear Numerical Analysis and Experiment of Composite Laminated Shell (복합재 적층셸의 비선형 수치해석 및 실험)

  • 조원만;이영신;윤성기
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.8
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    • pp.2051-2060
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    • 1993
  • A finite element program using degenerated shell element was developed to solve the geometric, material and combined nonlinear behaviors of composite laminated shell. The total Lagrangian method was implemented for geometric nonlinear analysis. The material nonlinear behavior was analyzed by considering the matrix degradation due to the progressive failure in the matrix and matrix-fiber interface after initial failure. The result of the geometric nonlinear analysis showed good agreement with the other exact and numerical solutions. The results of the combined analyses considered both geometric and material nonlinear analyses were compared with the experiments in which internal pressure was applied to the filament wound antisymmetric tubes.