• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.21-24
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• 2008

In this paper, Designed Quadrature hybrid coupler apply Open-PI equivalent transmission line. Using the proposed structure we achieve significant size reduction with the same results of conventional quadrature hybrid coupler at 912MHz. The measured frequency responses agree well with simulated one.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4_1
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• pp.77-85
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• 1992

The Pseudo-dynamic test is a new experimental technique for simulating the earthquake response of structures or structural components in the time domain. It is especially efficient for testing specimens that are too large, heavy or strong to be tested on a shaking table. But, in general, the responses obtained in the Pseudo-dynamic test can be distorted by the experimental errors inevitably during control and measurement procedures. The studies are to investigate the effects of the experimental errors on the Pseudo-dynamic responses and apply a correction method to the Pseudo-dynamic testing algorithm. It is shown that the corrected responses using the equivalent energy compensation method are in a good correlation with the theoretical ones. Thus, the corrected Pseudo-dynamic responses could be reliable for evaluating the seismic performance of structural systems.

• Journal of Korean Association for Spatial Structures
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• v.9 no.4
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• pp.49-59
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• 2009

The seismic responses of small-scale spatial frames such as school gymnasiums are usually evaluated using static analysis, although time-history analysis should be carried out to fully incorporate the dynamic responses of the structures against seismic motions. In this study, advanced static analysis procedures arc presented for school gymnasiums that will improve the performance evaluation against seismic motions. The seismic loads are approximated by equivalent static loads corresponding to the two performance levels; i.e., Levels 1 and 2 defined by the Japanese building standard. The importance of utilizing the eigenmode in the load pattern is discussed. Simple static analysis procedures are presented for evaluation of maximum vertical acceleration. It is shown that the static analysis for Level 2 input significantly underestimates the responses by dynamic analysis; however, the inelastic responses for Level 2 are shown to be successfully evaluated using the equivalent linearization that is similar to the $^{\circ}$Dmethod based on calculation of limit strength$^{\circ}{\pm}$ for building frames in Japan.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.27-30
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• 2007

This paper deals with an equivalent circuit model for RF passive components. Rational functions are obtained from the frequency responses of EM simulation by using Foster canonical partial fraction expressions. The Vector Fitting(VF) and the Adaptive Frequency Sampling(AFS) scheme are also implemented to obtain the rational functions. A passivity enforcement algorithm is applied to ensure the stability of the equivalent circuit model. In order to verify the schemes, S parameters of the equivalent circuit model is compared to those of EM simulation in case of the microstrip line structure with 3 slots in ground.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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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.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1990.10a
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• pp.73-78
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• 1990

In current practice of earthquake resistant design the equivalent lateral force procedure is widely used for its simplicity and convenience. But the equivalent lateral force procedure is derived based on the assumption that the dynamic behavior of the structure is governed primarily by the fundamental vibration mode. Therefore proper prediction of dynamic responses of the structure is unreliable using the equivalent lateral force procedure when the effect of higher vibration modes on the dynamic behavior is negligible. In this study design seismic load which can reflect the effect of higher vibration modes is proposed from the point of view of proper assessment of story shears which have the major influence on the design moment of beams and columns. To evaluate the effect of higher modes, differences between the story force based on the equivalent lateral force procedure specified in current earthquake resistance building code and the one based on modal analysis using design spectrum are examined. From these results improved design seismic load for the equivalent lateral force procedure which can reflect the effect of higher vibration modes is proposed.

• Structural Engineering and Mechanics
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• v.8 no.3
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• pp.299-310
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• 1999

One problem with base isolators of the sliding type is that their dynamic responses are nonlinear, which cannot be solved in an easy manner, as distinction must be made between the sliding and non-sliding phases. The lack of a simple method for analyzing structures installed with base isolators is one of the obstacles encountered in application of these devices. As an initial effort toward simplification of the analysis procedure for base-isolated structures, an approach will be proposed in this paper for computing the equivalent damping for the resilient-friction base isolators (R-FBI), based on the condition that the sum of the least squares of errors of the linearized response with reference to the original nonlinear one is a minimum. With the aid of equivalent damping, the original nonlinear system can be replaced by a linear one, which can then be solved by methods readily available. In this paper, equivalent damping curves are established for all ranges of the parameters that characterize the R-FBI for some design spectra.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.4 s.109
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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.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.1
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• pp.39-58
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• 2004

It is very important that predict the inelastic seismic behavior exactly for seismic performance evaluation of a building in the performance based seismic design. Evaluation method of seismic performance based on the pushover analysis reflected in PBSE was developed by some researchers. For the evaluation of inelastic global and local seismic responses by pushover analysis exactly. lateral load distribution should be adjusted and reflected the dynamic characteristics of structural system and various seismic ground motions. And performance point should be determined based on the evaluation of reasonable deformation capacity of a building more exactly. An effective method based on the improved the adaptive lateral load distribution and the equivalent responses of a multistory building is proposed in this study to efficiently estimate the accurate inelastic seismic responses. The proposed method can be used to evaluate the seismic performance for the global inelastic behavior of a building and to accurately estimate its local inelastic seismic responses. In order to demonstrate the accuracy and validity of this method, inelastic seismic responses estimated by the proposed method are compared with those obtained from other analytical methods.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.4
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• pp.458-467
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• 2012

In this study, the linear viscoelastic response of a rectangular laminated plate is investigated. The viscoelastic properties, expressed by two basic spring-dashpot models, that is Kelvin and Maxwell models, is assumed in the range to investigate the influence of viscoelastic coefficients to mechanical behavior. In the present study, viscoelastic responses are performed for two popular equivalent single-layered theories, such as the first-order shear deformation theory (FSDT) and third-order shear deformation theory (TSDT). Compliance and relaxation modulus of time-dependent viscoelastic behavior are approximately determined by Prony series. The constitutive equation for linear viscoelastic material as the Boltzmann superposition integral equation is simplified by the convolution theorem of Laplace transformation to avoid direct time integration as well as to improve both accuracy and computational efficiency. The viscoelastic responses of composite laminates in the real time domain are obtained by applying the inverse Laplace transformation. The numerical results of viscoelastic phenomena such as creep, cyclic creep and recovery creep are presented.