• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.449-453
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• 2010

본 논문에서는 점성 및 감쇠가 있는 단자유도 구조물의 등가감쇠비를 효율적으로 구하는 방법을 제시하였다. 건물에 설치된 마찰감쇠기는 외력의 크기에 따라 정지와 운동의 상태를 반복하여 외부 입력에너지를 소산시키기 때문에 외력과 응답관계가 비선형이다. 마찰감쇠기가 설치된 단자유도 건물은 마찰감쇠기외에 점성감쇠가 동시에 존재하므로 해석적인 정해를 구하기가 어렵다. 등가감쇠비를 산정하기 위해서 첫째, 점성과 마찰감쇠가 있는 단자유도계 건물의 자유진동 정해를 통하여 변위응답과 가속도 응답특성을 분석하였다. 둘째, 자유진동의 경우 응답이 멈출 때까지 소산에너지식을 이용하여 등가점성감쇠비를 구하였다. 셋째, 조화가진 일 때는 수치해석을 통하여 마찰력비 $F_r$에 따른 응답 특성을 알아보았다. 넷째, 조화가진의 경우 에너지 균형식을 바탕으로 등가점성감쇠비를 유도하였다. 등가점성감쇠비는 변위응답비의 영향을 받으므로 응답을 알아야만 구할 수 있다. 건물 응답의 진동수 특성은 협소영역(narrow band)이므로 고유진동수에 의해 지배된다고 가정하여 등가점성감쇠비를 구하였다. 마지막으로, 유도한 자유진동과 조화가진의 등 가점성감쇠비를 이용한 등가선형운동방정식의 해를 비선형 수치해석 한 결과와 비교하여 검증하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.12 no.3
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• pp.21-28
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• 2008

To evaluate the seismic performance of multi-degree of freedom(MDF) systems, repeated nonlinear response history analyses are often conducted, which require extensive computational efforts. To reduce the amount of computation required, equivalent single degree of freedom(SDF) systems representing complex multi-degree of freedom(MDF) systems have been developed. For the equivalent SDF systems, bilinear models and trilinear models have been most commonly used. In these models, the P-$\Delta$ effect due to gravity loads during earthquakes can be accounted for by assigning negative stiffness after elastic range. This study evaluates the adequacy of equivalent SDF systems having these hysteretic models to predict the actual response of steel moment resisting frames(SMRF). For this purpose, this study conducts cyclic pushover analysis, nonlinear time history analysis and incremental dynamic analysis(IDA) for SAC-Los Angeles 9-story buildings using nonlinear MDF models(exact) and equivalent SDF models(approximate). In addition, this study considers the strength limited model.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.473-484
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• 2006

The capacity spectrum method (CSM) can be used to simply estimate the maximum displacement response of the nonlinear structures. To evaluate seismic performance of multi-span bridges using the CSM, the representative response for structural system should be derived from the multi-degree-of-freedom (MDOF) responses by using the equivalent single-degree-of-freedom (ESDOF) method. The ESDOF method is used to calculate the capacity curve of the structural system from the pushover curves of all piers or structural members estimated by the pushover analysis. In order to evaluate an accuracy of ESDOF methods used in the CSM, the maximum displacements estimated by the CSM incorporating the several ESDOF methods are compared to those by the inelastic time-history analysis for several artificial earthquakes corresponding to the design spectrum.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.173-182
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• 2003

In equivalent static nonlinear analysis and in energy-based design, the structures are generally transformed into an equivalent SDOF system. In this study the seismic energy demands in multi story structures, such as three-, eight-, and twenty-story steel moment-resisting frames(MRF), buckling restrained braced frames(BRBF) and a damage tolerant braced frame(DTBF), are compared with those of equivalent single degree of freedom(ESDOF) systems. Sixty earthquake ground motions recorded In different soil conditions, which are soft rock, soft soil, and neat fault, were used to compute the input and hysteretic energy demands in model structures. In case the modal mass coefficient is less than 0.8, the effects of higher modes are considered in the process of converting into ESDOF According to the analysis results, the hysteretic and input energies obtained from 3 story and 8 story MRF and DTBF agreed well with the results from analysis of equivalent SDOF systems. However in the 20 story BRBF the results from ESDOF underestimated those obtained from the original structures.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.71-80
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• 2003

Though a nonlinear time history analysis may be provided to estimate more exactly the seismic performance of building structure, approximation methods are still needed in the aspect of practicality and simplicity, In converting a multi-story structure to an equivalent SDOF system, the mode vectors of the multi-story structure are assumed as the mode shape in elastic state regardless of elastic or elastic-plastic state. However, the characteristics of displacement mode are also changed after the yielding made in the structural elements, because the structure becomes inelastic in each incremental load step. In this research, a method of converting MDOF system to ESDOF system is presented by using nonlinear displacement mode considering the mode change of structures after the yielding. Also, the accuracy and efficiency of the method of the nonlinear displacement mode method of the estimate of seismic response of Mixed Building Structures were examined by comparing the displacements of the roof level of the multi-story building structures estimated from this converted displacement response of ESDOF with the displacement of the roof level through the nonlinear dynamic analysis of the multi-story building structures subjected to an actual earthquake excitation.

• Journal of Korean Society of Steel Construction
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• v.27 no.3
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• pp.273-280
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• 2015

Equivalent Single-Degree-of-Freedom(SDOF) analysis, most used for blast-resistant design, does not consider the effects of gravity load on the performance evaluation of blast resistance of structural members. However, since there exists gravity load on columns and walls of structures, the blast resistance of structural members should be evaluated considering gravity load on them. In this paper, an approach to reflect the gravity load effects on the equivalent SDOF analysis for dynamic blast response of structural members is proposed. For this purpose, the parametric studies using finite element analysis were performed by varying maximum blast load, blast load duration, and gravity load with constant the resistance and natural period of a structural member. The finite element analysis results were compared with the equivalent SDOF analysis results and the blast response of the structure member was estimated by conducting finite element analyses for various gravity loads. Finally, a graphical solution for ductility of a structural member with the variables of blast load, gravity load and structural member properties was developed. The blast response of structural members under gravity load could be estimated reasonably and easily by using this graphical solution.

• 건축구조
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• v.13 no.1
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• pp.46-58
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• 2006

구조동력학 이론에 기초하여 내진설계 기술이 개발되었다. 그러므로 건축물의 내진설계를 근본적으로 이해하기 위해서는 구조동력학의 여러 가지 이론들을 먼저 알고 이들이 내진설계에 어떻게 적용이 되는지를 알아야 한다. 이 글은 구조기술자 여러분이 건축물의 내진설계를 이해하는데 도움이 될 수 있도록 하기 위하여 다음과 같이 3부로연재될예정이다. 제1부: 응답스펙트럼과구조물의동적해석 제2부: 등가정적해석법과반응수정계수의배경 제3부: 능력스펙트럼법에의한비탄성해석 제1부에서는 단자유도 구조물의 지진해석을 통하여 응답스펙트럼을 작성하는 원리와 이를 이용하여 간편하게 지진해석을 수행하는 방법을 소개하고 응답스펙트럼에 근거하여 설계응답스펙트럼을 작성하는 방법과 다자유도 구조물의 지진응답을 알아내기 위한 응답 스펙트럼 해석법에 관하여 소개한다. 제2부에서는 구조동력학 이론에 근거하여 등가정적해석법이 유도된 근거와 반응수정계수를 사용하게 되는 배경을 소개하여 구조기술자들이내진설계에좀더확실한이해를할수있도록할것이다. 마지막으로 제3부에서는 비탄성해석을 좀 더 쉽게 하기 위하여 사용되는 능력스펙트럼법의 배경과 이를 이용하여 건축물의 성능점을 찾는 방법과 구조물의 비탄성 지진응답을 평가하는 방법에 대하여 소개함으로써 성능에 기초한 내진설계를 위한 기초 이론을 확실히 이해할수있도록할것이다. 구조동력학에 관한 내용을 여기에 상세히 소개하자면 엄청난 분량이 될 것이므로 여기서는 이 글을 읽는 구조기술자들이 구조동력학에 관한 기초적인 내용을 이해하고 있는 것으로 가정하기로 한다. 그러므로 구조동력학에 대한 기초적 이론을 확실히 이해하고 있지 못한분들은이글을읽기전에먼저구조동력학에관한알기쉬운서적을 먼저 읽도록 추천한다.

• Journal of Industrial Technology
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• v.25 no.A
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• pp.23-30
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• 2005

The capacity spectrum method(CSM) can be used for the evaluation of inelastic maximum response of structures and has been recently used in the seismic design using the incorporation of pushover analysis and response spectrum method. To efficiently evaluate seismic performance of multi-degree-of freedom(MDOF) bridge structures, it is important that the equivalent response of MDOF bridge structures should be calculated. To calculate the equivalent response of MDOF system, equivalent responses are obtained by using Song method, Fajfar method and Calvi method. Also, those responses are applied to CSM method and seismic performance of bridge according to the ESDOF method are compared and evaluated straightforwardly.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.199-208
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• 2010

A friction damper installed at a building shows nonlinear behavior since its stick and slip states are occurred repeatedly depending on the amplitude of external loadings to dissipate input energy. Friction damping is existed for the building with a friction damper. In additionally viscous one is inherently included. Therefore, the building installed in such combined damping is quite involved to find the analytical solution. In this study, first, displacement and acceleration characteristics are identified based on the exact solution for a single-degree-freedom building with a friction damper having both friction and viscous damping. Second, in free vibration, the equivalent viscous damping ratio is obtained by the energy dissipation. Third, numerical analysis is carried out to find response configuration with various friction force ratios. Fourth, corresponding equivalent viscous damping ratio is derived with the finding that the response reaches into steady-state for both friction and viscous damped structure. It is deduced using balance of input external energy and output dissipation energy for steady-state response. Finally, the equivalent viscous damping ratios of free or harmonic vibration are verified through nonlinear analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9A
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• pp.1434-1441
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• 1999

This paper presents an equivalent circuit of the hairpin line filter for accurate analysis and design. Its validity was verified by computer simulations and filter design experiments. Though the various design equations for a hairpin line filter have been proposed, there has not been a practically simplified equivalent circuit because it is hard to effectively represent interconnection effects between non-adjacent elements. In this paper, all the open ports of the hairpin line filter circuit are changed to the short ports using circuit duality, and the resulting circuits are transformed to graph model. The further simplified circuit model is obtained from boundary conditions, and then the final equivalent circuit of the hairpin line filter is derived in a dual structure of the filter.