• Title, Summary, Keyword: equivalent linear model

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Seismic Fragility Analysis of Seismically Isolated Nuclear Power Plant Structures using Equivalent Linear- and Bilinear-Lead Rubber Bearing Model (등가선형 및 이선형 납-고무받침 모델을 적용한 면진된 원전구조물의 지진 취약도 해석)

  • Lee, Jin-Hi;Song, Jong-Keol
    • Journal of the Earthquake Engineering Society of Korea
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    • v.19 no.5
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    • pp.207-217
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    • 2015
  • In order to increase seismic performance of nuclear power plant (NPP) in strong seismic zone, lead-rubber bearing (LRB) can be applied to seismic isolation system of NPP structures. Simple equivalent linear model as structural analysis model of LRB is more widely used in initial design process of LRB than a bilinear model. Seismic responses for seismically isolated NPP containment structures subjected to earthquakes categorized into 5 different soil-site classes are calculated by both of the equivalent linear- and bilinear- LRB models and compared each others. It can be observed that the maximum displacements of LRB and shear forces of containment in the case of the equivalent linear LRB model are larger than those in the case of bilinear LRB model. From the seismic fragility curves of NPP containment structures isolated by LRB, it can be observed that seismic fragility in the case of equivalent linear LRB model are about 5~30 % larger than those in the case of bilinear LRB model.

Comparison of Seismic Responses of Seismically Isolated NPP Containment Structures using Equivalent Linear- and Nonlinear-Lead-Rubber Bearing Modeling (등가선형 및 비선형 납-고무받침 모델을 이용한 면진된 원전구조물의 지진응답의 비교)

  • Lee, Jin Hi;Song, Jong-Keol
    • Journal of the Earthquake Engineering Society of Korea
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    • v.19 no.1
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    • pp.1-11
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    • 2015
  • In order to perform a soil-isolation-structure interaction analysis of seismically isolated nuclear power plant (NPP) structures, the nonlinear behavior of a seismic isolation system may be converted to an equivalent linear model used in frequency domain analysis. Seismic responses for seismically isolated NPP containment structures subjected to a simple artificial acceleration history and different site class earthquakes are evaluated for the equivalent-linear and nonlinear models that have been applied to lead-rubber bearing (LRB) modeling. It can be observed that the maximum displacements of the equivalent linear model are larger than that of the nonlinear model. From the floor response spectrum analysis for the top of NPP containment structures, it can be observed that the spectral acceleration of an equivalent linear model at about 0.5 Hz frequency is about 2~3 times larger than that of a nonlinear model.

A new practical equivalent linear model for estimating seismic hysteretic energy demand of bilinear systems

  • Samimifar, Maryam;Massumi, Ali;Moghadam, Abdolreza S.
    • Structural Engineering and Mechanics
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    • v.70 no.3
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    • pp.289-301
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    • 2019
  • Hysteretic energy is defined as energy dissipated through inelastic deformations during a ground motion by the system. It includes frequency content and duration of ground motion as two remarkable parameters, while these characteristics are not seen in displacement spectrum. Since maximum displacement individually cannot be the appropriate criterion for damage assessment, hysteretic energy has been evaluated in this research as a more comprehensive seismic demand parameter. An innovative methodology has been proposed to establish a new equivalent linear model to estimate hysteretic energy spectrum for bilinear SDOF models under two different sets of earthquake excitations. Error minimization has been defined in the space of equivalent linearization concept, which resulted in equivalent damping and equivalent period as representative parameters of the linear model. Nonlinear regression analysis was carried out for predicting these equivalent parameter as a function of ductility. The results also indicate differences between seismic demand characteristics of far-field and near-field ground motions, which are not identified by most of previous equations presented for predicting seismic energy. The main advantage of the proposed model is its independency on parameters related to earthquake and response characteristics, which has led to more efficiency as well as simplicity. The capability of providing a practical energy based seismic performance evaluation is another outstanding feature of the proposed model.

Experimental Study on the Probability-based Equivalent Linearization of a Friction Damper-Brace System (마찰감쇠기-가새 시스템의 확률분포 기반 등가선형화에 관한 실험적 연구)

  • Kang, Kyung-Soo;Park, Ji-Hun
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.16 no.4
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    • pp.394-403
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    • 2006
  • A new equivalent linearization technique is proposed for a friction damper-brace system (FDBS) idealized as a elastoplastic system. The equivalent linearization technique utilizes secant stiffness and dissipated energy defined by the probability distribution of the extremal displacement of the FDBS. In addition, a conversion scheme is proposed so that an equivalent linear system is designed first and converted to the FDBS. For comparative study, an existing model update technique based on system identification is modified in a form appropriate to update single element. For the purpose of verification, shaking table tests of a small scale three-story shear building model, in which a rotational FDBS is installed, are conducted and equivalent linear systems are obtained using the proposed technique and the model update technique. Complex eigenvalue analysis is conducted for those equivalent linear systems, and the natural frequencies and modal damping ratios are compared with those obtained from system identification. Additionally, RMS and peak responses obtained from time history analysis of the equivalent linear systems are compared with measured ones.

Simplified 3D Finite Element Analysis of Linear Inductor Motor for Integrated Magnetic Suspension/Propulsion Applications (자기부상 및 추진 일체형 리니어 인덕터 모터의 간이형 3차원 유한요소해석)

  • Jeong, Sang-Sub;Jang, Seok-Myeong
    • The Transactions of the Korean Institute of Electrical Engineers B
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    • v.49 no.6
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    • pp.371-379
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    • 2000
  • The 4-pole linear homopolar synchronous motor (LHSM), so called linear inductor motor, is composed of the figure-of-eight shaped 3-phase armature windings, DC field windings, and the segmented secondary with the transverse bar track. To reduce the calculation time, the simplified 3D finite element model with equivalent reluctance and/or permanent magnet is presented. To obtain a clear understanding, propriety and usefulness of the developed model, we compare with the results of simplified 3D FEA, general 3D FEA and test. Consequently, the results of simplified and 3D FEM analysis are nearly identical, but much larger than that of static test at d-axis armature excitation. Therefore the improved FEA model, such as full model with half slot, is needed for the precise analysis.

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Study on the Generalization of the Equivalent Point Method for Thermal Evaluation (Equivalent Point Method의 일반적 이용을 위한 연구)

  • Rhim, Jong-Whan
    • Korean Journal of Food Science and Technology
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    • v.22 no.5
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    • pp.575-581
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    • 1990
  • The existence of the equivalent point for a thermal processing system was demonstrated using arbitrarily chosen ideal direct heating curves. i.e. isothermal heating curves at $120^{\circ}C$ for 10min and at $135^{\circ}C$ for 10sec. Under these conditions, G-values and F-values were calculated at various values of Ea- and z-values by applying the Arrhenius and the Bigelow models respectively. The equivalent time and equivalent temperature were determined by both line intersection and linear regression methods. The equivalent points estimated by both the line intersection and the linear regression methods were consistent and their values were the same as the heating time and temperature of the ideal direct heating curves.

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Evaluation of numerical procedures to determine seismic response of structures under influence of soil-structure interaction

  • Tabatabaiefar, Hamid Reza;Fatahi, Behzad;Ghabraie, Kazem;Zhou, Wan-Huan
    • Structural Engineering and Mechanics
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    • v.56 no.1
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    • pp.27-47
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    • 2015
  • In this study, the accuracy and reliability of fully nonlinear method against equivalent linear method for dynamic analysis of soil-structure interaction is investigated comparing the predicted results of both numerical procedures with the results of experimental shaking table tests. An enhanced numerical soil-structure model has been developed which treats the behaviour of the soil and the structure with equal rigour. The soil-structural model comprises a 15 storey structural model resting on a soft soil inside a laminar soil container. The structural model was analysed under three different conditions: (i) fixed base model performing conventional time history dynamic analysis, (ii) flexible base model (considering full soil-structure interaction) conducting equivalent linear dynamic analysis, and (iii) flexible base model performing fully nonlinear dynamic analysis. The results of the above mentioned three cases in terms of lateral storey deflections and inter-storey drifts are determined and compared with the experimental results of shaking table tests. Comparing the experimental results with the numerical analysis predictions, it is noted that equivalent linear method of dynamic analysis underestimates the inelastic seismic response of mid-rise moment resisting building frames resting on soft soils in comparison to the fully nonlinear dynamic analysis method. Thus, inelastic design procedure, using equivalent linear method, cannot adequately guarantee the structural safety for mid-rise building frames resting on soft soils. However, results obtained from the fully nonlinear method of analysis fit the experimental results reasonably well. Therefore, this method is recommended to be used by practicing engineers.

Closed Form Formulas for Equivalent Damping Ratios of a Linear Structure Equipped with Damping Devices (제진장치가 설치된 구조물의 등가감쇠비)

  • Hwang, Jae-Seung;Lee, Sang-Hyun;Min, Kyung-Won
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.370-377
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    • 2002
  • Hwang et al (2001) proposed a new method for an evaluation of equivalent damping ratios of a linear structure with linear or nonlinear damping devices. This procedure has a disadvantage that it requires time history analysis for the whole system including damping devices, which may be troublesome for practical application. To tackle this problem closed form formulas for equivalent damping ratios are proposed in this study. It is assumed that the responses of MDOF system can be reproduced by an equivalent SDOF system which vibrates in a fundamental mode. The numerical analyses of a ten-story building equipped with linear viscous damper or active mass damper or friction damper show the effectiveness of equivalent SDOF model and closed form formulas.

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Experimental Study on Equivalent Linear System for Rotational friction Damper (회전마찰감쇠기의 등가선형시스템에 관한 실험적 연구)

  • 김형섭;박지훈;민경원;이상현;이명규
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.296-303
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    • 2004
  • In this study, equivalent linear damping and stiffness of a single-degree-of-freedom (SDOF) structure with a rotational friction damper are estimated using the result of experiments and compared with those obtained from non-linear time history analyses. First, the transfer function of the test model is constructed and then the equivalent stiffness and damping are calculated, using the half-power bandwidth (HPB) method. For comparative study, those properties are estimated based on stochastic theory in the time domain. Both equivalent linear systems identified from experiments and numerical analyses correspond well. Further, it is observed that there exists an optimal clamping force on the rotational friction damper from estimated equivalent damping.

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A Study on Equivalent Model of EEFL Based on the Equivalent Resistance and Capacitance Variation (등가 저항과 등가 커패시터 변화에 바탕을 둔 외부전극 형광램프의 등가모델 연구)

  • Cho Kyu-Min;Oh Won-Sik;Moon Gun-Woo;Park Mun-Soo;Lee Sang-Gil
    • Proceedings of the KIPE Conference
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    • pp.59-61
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    • 2006
  • A circuit model simulating the electrical characteristics of EEFL(External Electrode Fluorescent Lamp) is proposed. The model is based on linear approximation that represents the equivalent resistance and capacitance as a function of power. Simulation waveforms and experimental results are presented to verify feasibility of the equivalent model.

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