• 제목/요약/키워드: Linear response

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구분적선형시스템을 이용한 해양 구조물의 거동분석 (Analysis of Response behaviors of offshore mooring structures by a piecewise-linear system)

  • 마호성
    • 전산구조공학
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    • 제10권4호
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    • pp.251-265
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    • 1997
  • 해양계선시스템(offshore mooring system)의 거동을 구분적선형시스템(piecewise-linear system)을 이용하여 분석하였다. 계선시스템의 복원력을 유도하고 거기에 상응하는 근사치 구분적선형시스템의 복원력을 구하여 두 시스템의 복원력을 비교하였다. 다양한 파력 하에서의 계선시스템의 응답거동을 분석하였다. 시스템의 비선형정도 및 매개변수의 영향에 대하여 집중적으로 연구하였다. 시스템의 응답거동의 특성은 포인케어맵(Poincare map)을 통하여 확인하였다. 구분적선형시스템을 이용하여 분석한 결과, 계선시스템은 일반 조화, 열조화 및 복잡한 비선형거동인 chaos를 포함한 다양한 응답거동을 갖음을 알아냈다. 여러 값의 매개변수를 적용하여 시스템의 응답거동에 미치는 영향을 알아냈으며, 매개변수지도를 통하여 응답거동의 영역을 확인하였다.

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

  • 김용일;박경진
    • 대한기계학회논문집A
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    • 제31권11호
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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.

Monotone Local Linear Quasi-Likelihood Response Curve Estimates

  • Park, Dong-Ryeon
    • Communications for Statistical Applications and Methods
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    • 제13권2호
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    • pp.273-283
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    • 2006
  • In bioassay, the response curve is usually assumed monotone increasing, but its exact form is unknown, so it is very difficult to select the proper functional form for the parametric model. Therefore, we should probably use the nonparametric regression model rather than the parametric model unless we have at least the partial information about the true response curve. However, it is well known that the nonparametric regression estimate is not necessarily monotone. Therefore the monotonizing transformation technique is of course required. In this paper, we compare the finite sample properties of the monotone transformation methods which can be applied to the local linear quasi-likelihood response curve estimate.

공진형 선형 액추에이터의 감쇄지수 변화에 따른 과도 응답특성 (Transient Response of a linear actuator with a damping ratio)

  • 우병철;강도현
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2004년도 하계학술대회 논문집 B
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    • pp.1037-1039
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    • 2004
  • A typical conventional systems of a linear motion use rack and pinions or ball screws to convert rotary motions from DC servo motors. A linear motor has been used a several field for a MEMS technology and a aircraft carrier. We was studied a transient response of a linear actuator with a damping ratio, spring constant and a pressed power.

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Comparison of linear and non-linear earthquake response of masonry walls

  • Sayin, Erkut;Calayir, Yusuf
    • Computers and Concrete
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    • 제16권1호
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    • pp.17-35
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    • 2015
  • In this study, linear and non-linear response of a masonry wall that includes an opening was presented. The masonry wall was modeled with two-dimensional finite elements. Smeared crack model that includes the strain softening behavior was selected to the masonry wall material. For the numerical application, linear and non-linear analyses of the masonry wall were carried out using east-west and vertical components of the 1992 Erzincan and 2003 $Bing{\ddot{o}}l$ earthquake acceleration records. Linear and non-linear solutions were compared each other. The displacement and stress results at the selected points of the masonry wall and crack propagation in the masonry wall were presented for both earthquake acceleration records.

등가하중을 이용한 원자로 핵연료봉 지지격자 스프링의 비선형 응답 구조 최적설계 (Nonlinear Response Structural Optimization of a Nuclear Fuel Rod Spacer Grid Spring Using the Equivalent Load)

  • 김도원;이현아;송기남;김용일;박경진
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2007년도 춘계학술대회A
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    • pp.694-699
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    • 2007
  • The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring,nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are teansformed 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 no EL. The objective function is defined by minimizing the maximum stress in the spring while is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

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Improvement of Group Delay and Reduction of Computational Complexity in Linear Phase IIR Filters

  • Varasumanta, Saranuwaj;Sookcharoenphol, Dolchai;Sriteraviroj, Uthai;Janjitrapongvej, Kanok;Kanna, Channarong
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2003년도 ICCAS
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    • pp.955-959
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    • 2003
  • A technique for realizing linear phase IIR filters has been proposed by Powell-Chau which gives a real-time implementation of H(z-1).H(z), where H(z) is a causal nonlinear phase IIR filter. Powell-Chau system is linear but not timeinvariant system. Therefore, that system has group delay response that exhibits a minor sinusoidal variation superimposed on a constant value. In the signal processing, this oscillation seriously degrade the signal quality. Unfortunately, that system has a large sample delay of 4L and also more computational complexity. Proposed system is present a reduced computational complexity technique by moved the numerator polynomial of H(1/z) out to cascade with causal filter H(z) and remain only all-pole of H(1/z), then applied truncated infinite impulse response to finite with truncated IIR filtel $H_L$(z) and L sample delay to subtract the output sequence from the top and bottom filter. Proposed system is linear time invariance and group delay response and total harmonic distortion are also improved.

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지진 안전도 해석을 위한 Twisted Tripod 지지 구조를 갖는 풍력발전기의 말뚝-지반 상호작용 모델 평가 (Evaluation of Pile-Ground Interaction Models of Wind Turbine with Twisted Tripod Support Structure for Seismic Safety Analysis)

  • 박광연;박원석
    • 한국안전학회지
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    • 제33권1호
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    • pp.81-87
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    • 2018
  • The seismic response, the natural frequencies and the mode shapes of an offshore wind turbine with twisted tripod substructure subject to various pile-ground interactions are discussed in this paper. The acceleration responses of the tower head by four historical earthquakes are presented as the seismic response, while the other loads are assumed as ambient loads. For the pile-ground interactions, the fixed, linear and nonlinear models are employed to simulate the interactions and the p-y, t-z and Q-z curves are utilized for the linear and nonlinear models. The curves are designed for stiff, medium and soft clays, and thus, the seven types of the pile-ground interactions are used to compare the seismic response, the acceleration of the tower head. The mode shapes are similar to each other for all types of pile-ground interactions. The natural frequencies, however, are almost same for the three clay types of the linear model, while the natural frequency of the fixed support model is quite different from that of the linear interaction model. The wind turbine with the fixed support model has the biggest magnitude of acceleration. In addition, the nonlinear model is more sensitive to the stiffness of clay than the linear pile-ground interaction model.

Effectiveness of non-linear fluid viscous dampers in seismically isolated buildings

  • Guler, Elif;Alhan, Cenk
    • Earthquakes and Structures
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    • 제17권2호
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    • pp.191-204
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    • 2019
  • Near-field earthquake records including long-period high-amplitude velocity pulses can cause large isolation system displacements leading to buckling or rupture of isolators. In such cases, providing supplemental damping in the isolation system has been proposed as a solution. However, it is known that linear viscous dampers can reduce base displacements in case of near-field earthquakes but at the potential expense of increased superstructure response in case of far-field earthquakes. But can non-linear dampers with different levels of non-linearity offer a superior seismic performance? In order to answer this question, the effectiveness of non-linear viscous dampers in reducing isolator displacements and its effects on the superstructure response are investigated. A comparison with linear viscous dampers via time history analysis is done using a base-isolated benchmark building model under historical near-field and far-field earthquake records for a wide range of different levels of non-linearity and supplemental damping. The results show that the non-linearity level and the amount of supplemental damping play important roles in reducing base displacements effectively. Although use of non-linear supplemental dampers may cause superstructure response amplification in case of far-field earthquakes, this negative effect may be avoided or even reduced by using appropriate combinations of non-linearity level and supplemental damping.

지반응답해석기법의 차이에 의한 지반응답 분산도 평가 (Influence of Analysis Models on Variation of Ground Response during Earthquake)

  • 김성렬;최재순;김수일;박대영;박성용;김기풍
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2007년 가을학술발표회
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    • pp.317-333
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    • 2007
  • The Round-Robin Test (RRT) for ground response analysis was performed by Division of Geotechnical Earthquake Engineering of Korean Geotechnical Society. This research analyzed the influence of analysis methods on variation of ground response by using the results of this RRT. The analysis methods include equivalent linear analysis, non-linear analysis and effective stress analysis. A total of 5 teams among 12 teams applied two kinds of analysis methods. This research compared the results of these 5 teams and analyzed the variation of the results according to analysis methods. The compared results were shear stress-shear strain relation, transfer function, time history and the response spectrum of ground surface acceleration, peak ground acceleration, peak shear strain and maximum excess pore pressure ratio.

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