• 한국지진공학회논문집
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• 제9권5호
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• pp.75-86
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• 2005

성능에 기초한 설계법에서는 비선형 응답산정이 필수적이다. 이를 위한 해석법으로는 비선형 시간이력해석, 비선형 정적해석 혹은 비선형의 영향을 고려한 등가정적해석 등이 있다. 비선형 응답을 산정하기 위한 가장 정확한 해석방법은 비선형 시간이력해석법이지만, 많은 시간과 노력을 필요로 한다. 비선형 직접스펙트럼법은 pushover곡선으로부터 구조물의 선형 진동주기와 항복강도를 구한 다음, 반복계산 없이 비선형 응답을 직접 산정하는 약산법이다. 본 연구에서는 비선형 약산법들의 정확성과 신뢰성을 다양한 지진과 전단형 건물의 여러 가지 조건에 대해 검토하고자 한다. 본 연구의 결론은 다음과 같다. 1) 선형 능력스펙트럼법에 의한 약산응답들은 수렴하는 해를 구하지 못하거나 발산하는 경우가 발생하며 수렴하더라도 큰 오차가 발생하는 경우가 있으며, 지진별로 오차의 편차가 크다. 2) 비선형 능력스펙트럼법은 능력스펙트럼법보다 계산량이 크게 줄어들고, 해는 구해지나 요구곡선의 특성으로 정확한 해를 구하기 어려울 수 있으며, 전반적으로 큰 오차가 발생한다. 3) 비선형 직접스펙트럼법은 다른 약산법들에 비해 추가적이고 반복적인 계산과정 없이 pushover곡선과 비선형 응답스펙트럼으로부터 비교적 정확한 값을 직접 구할 수 있으므로 실용적인 방법으로 사료된다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.241-244
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• 1996

This paper discusses the general properties and the design procedures of Internal Model Control(IMC) scheme for nonlinear plants. Also we propose new nonlinear IMC(NIMC) design method using linear IMC. Although all IMC controllers can be thought simple 'inverse controller', its nonlinear realization is not easy. Propose NIMC is composed multiple linear models, IMC controllers, and switching scheme. The advantages of this method are we can use simple linear IMC design method and need not nonlinear modelings.

• 대한수학회논문집
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• 제12권2호
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• pp.467-478
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• 1997

A nonlinear Galerkin method for the Burgers equation is considered. Due to the lack of the divergence free condition, the nonlinear term is treated differently compared to that of the Navier-Stokes equations. Strong convergence results are proved for the nonlinear Galerkin method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.71-78
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• 2005

In performance-based design methods, it is clear that the evaluation of the nonlinear response is required. The methods available to the design engineer today are nonlinear tim history analyses, or monotonic static nonlinear analyses, or equivalent static analyses with simulated inelastic influences. The nonlinear time analysis is the most accurate method in computing the nonlinear response of structures, but it is time-consuming and necessitate more efforts. Some codes proposed the capacity spectrum method based on the nonlinear static analysis to determine earthquake-induced demand given the structure pushover curve. This procedure is conceptually simple but iterative and time consuming with some errors. The nonlinear direct spectrum method is proposed and studied to evaluate nonlinear response of structures, without iterative computations, given by the structural linear vibration period and yield strength from the pushover analysis. The purpose of this paper is to compare the accuracy and the reliability of approximate nonlinear methods with respect to RC dual system and various earthquakes.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.597-600
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• 1997

In this paper, the authors propose a new method for linearizing a nonlinear dynamical system by use of polynomial compensation. In this method, an M-sequence is applied to the nonlinear system and the crosscorrelation function between the input and the output gives us every crosssections of Volterra kernels of the nonlinear system up to 3rd order. We construct a polynomial compensation function from comparison between lst order Volterra kernel and high order kernels. The polynomial compensation function is, in this case, of third order whose coefficients are variable depending on the amplitude of the input signal. Once we can get compensation function of nonlinear system, we can construct a linearization scheme of the nonlinear system. That is. the effect of second and third order Volterra kernels are subtracted from the output, thus we obtain a sort of linearized output. The authors applied this method to a saturation-type nonlinear system by simulation, and the results show good agreement with the theoretical considerations.

• Steel and Composite Structures
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• 제25권4호
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• pp.497-503
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• 2017

In this paper, nonlinear vibration of multi-degree of freedom systems are studied. It has been tried to develop the mathematical model of systems by second-order nonlinear partial differential equations. The masses are connected with linear and nonlinear springs in series. A great effort has been done to solve the nonlinear governing equations analytically. A new analytical method called Variational Iteration Method (VIM) is proposed and successfully applied to the problem. The linear and nonlinear frequencies are obtained and the results are compared with numerical solutions. The first order of Variational Iteration Method (VIM) leads us to high accurate solution.

• Coupled systems mechanics
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• 제7권6호
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• pp.691-705
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• 2018

In this paper, nonlinear displacements of laminated composite beams are investigated under non-uniform temperature rising with temperature dependent physical properties. Total Lagrangian approach is used in conjunction with the Timoshenko beam theory for nonlinear kinematic model. Material properties of the laminated composite beam are temperature dependent. In the solution of the nonlinear problem, incremental displacement-based finite element method is used with Newton-Raphson iteration method. The distinctive feature of this study is nonlinear thermal analysis of Timoshenko Laminated beams full geometric non-linearity and by using finite element method. In this study, the differences between temperature dependent and independent physical properties are investigated for laminated composite beams for nonlinear case. Effects of fiber orientation angles, the stacking sequence of laminates and temperature on the nonlinear displacements are examined and discussed in detail.

• Structural Engineering and Mechanics
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• 제64권2호
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• pp.259-270
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• 2017

The stochastic vibration response of the sandwich beam with the nonlinear adjustable visco-elastomer core and supported mass under stochastic support motion excitations is studied. The nonlinear dynamic properties of the visco-elastomer core are considered. The nonlinear partial differential equations for the horizontal and vertical coupling motions of the sandwich beam are derived. An analytical solution method for the stochastic vibration response of the nonlinear sandwich beam is developed. The nonlinear partial differential equations are converted into the nonlinear ordinary differential equations representing the nonlinear stochastic multi-degree-of-freedom system by using the Galerkin method. The nonlinear stochastic system is converted further into the equivalent quasi-linear system by using the statistic linearization method. The frequency-response function, response spectral density and mean square response expressions of the nonlinear sandwich beam are obtained. Numerical results are given to illustrate new stochastic vibration response characteristics and response reduction capability of the sandwich beam with the nonlinear visco-elastomer core and supported mass under stochastic support motion excitations. The influences of geometric and physical parameters on the stochastic response of the nonlinear sandwich beam are discussed, and the numerical results of the nonlinear sandwich beam are compared with those of the sandwich beam with linear visco-elastomer core.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1366-1371
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• 2006

A structural coupling method is developed for the dynamic analysis of a nonlinear structure with concentrated nonlinear hinge joints or sliding lines. Component mode synthesis method is extended to couple substructures and the nonlinear models. In order to verify the improved coupling method, a numerical plate model consisting of two substructures and torsional springs, is synthesized by using the proposed method and its model parameters are compared with analysis data. Then the coupling method is applied to a three-substructure-model with the nonlinearity of sliding lines between the substructures. The coupled structural model is verified from its dynamic analysis. The analysis results show that the improved coupling method is adequate for the structural nonlinear analyses with the nonlinear hinge and sliding mode condition.

• 한국구조물진단유지관리공학회 논문집
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• 제6권3호
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• pp.129-138
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• 2002

The purpose of this study is to propose the nonlinear analysis method which combines the nonlinear incremental method with the layered method to solve the problems due to the geometric and the material nonlinearities. As numerical analysis models, the reinforced concrete simple beam and the steel arch frame are used to verify the algorithm of the proposed nonlinear method. The results are gotten from the computation procedures. According to the results of this study, the fracture pattern of the beam according to the ratio of tensile steel and the strength of the concrete and the steel can be estimated by the proposed method. Therefore, the load-deflection curve of structure can be, exactly, depicted by the proposed method. Also, the rupture load, the site and the depth of crack of the beam can analytically be checked by the proposed method. In this respect, the proposed method contributes for the solving the stability problem of the actual structure.