• Steel and Composite Structures
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• 제36권4호
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• pp.399-415
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• 2020

Responses of semi-rigid frames having different degrees of semi-rigidity obtained by the nonlinear static analysis (NSA) are evaluated at specific target displacements by comparing them with those obtained by the nonlinear time-history analysis (NTHA) for scaled earthquakes. The peak ground accelerations (PGA) of the earthquakes are scaled such that the obtained peak top story displacements match with the target displacements. Three different types of earthquakes are considered, namely, far-field and near-field earthquakes with directivity and fling-step effects. In order to make the study a comprehensive one, three degrees of semi-rigidity (one fully rigid and the other two semi-rigid), and two frames having different heights are considered. An ensemble of five-time histories of ground motion is included in each type of earthquake. A large number of responses are considered in the study. They include the peak top-story displacement, maximum inter-story drift ratio, peak base shear, total number of plastic hinges, and square root of sum of the squares (SRSS) of the maximum plastic hinge rotations. Results of the study indicate that the nonlinear static analysis provides a fairly good estimate of the peak values of top-story displacements, inter-story drift ratio (for shorter frame), peak base shear and number of plastic hinges; however, the SRSS of maximum plastic hinge rotations in semi-rigid frames are considerably more in the nonlinear static analysis as compared to the nonlinear time history analysis.

• 한국전산구조공학회논문집
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• 제28권5호
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• pp.467-475
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• 2015

본 논문에서는 구조물에 작용하는 하중의 크기와 진동수에 따른 거동의 비선형성을 확인하고 정확한 예측을 위한 방법을 모색하기 위하여 외팔보의 정적 및 동적해석의 수행에서 선형, 비선형 해석의 결과를 비교하는 연구를 진행하였다. 우선 보의 자유단에 수직방향의 정적 및 동적 하중을 가한 상황을 예측하였다. 선형 해석방법으로 고전 외팔보 이론을 적용하였고, co-rotational dynamic 유한요소해석 기법을 개발하여 비선형 해석방법으로 사용하였다. 먼저 정적해석에서 외력의 크기가 달라질 때 선형 및 비선형 해석 예측이 어떠한 차이를 보이는지 비교하였다. 그리고 동적해석을 통해 가진 진동수의 변화에 따른 보 끝단의 무차원화된 변위의 양상을 연구하였고, 공진진동수 근방에서의 상당한 변위가 발생함을 보였다. 마지막으로 주파수 지연현상을 조사하기 위해 특정 진동수에서의 시간 경과에 따른 보의 변위를 확인하였다.

• Structural Engineering and Mechanics
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• 제58권2호
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• pp.327-345
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• 2016

Many experimental and analytical studies have been conducted with beam-column subassemblages composed of a two-span beam to investigate the progressive collapse resistance of RC frames. Most study results reveal a strength-decreased transition phase in the nonlinear static load-deflection curve, which may induce dynamic snap-through response and increase the chord rotation demand for effective catenary action (ECA). In this study, the nonlinear static response is idealized as a piecewise linear curve and analytical pseudo-static response is derived for each linearized region to investigate the rotation demands for the ECA of the two-span RC beams. With analytical parameters determined from several published test results, numerical analysis results indicate that the rotation demand of 0.20 rad recommended in the design guidelines does not always guarantee the ECA. A higher rotation demand may be induced for the two-span beams designed with smaller span-to-depth ratios and it is better to use their peak arch resistance (PAR) as the collapse strength. A tensile reinforcement ratio not greater than 1.0% and a span-to-depth ratio not less than 7.0 are suggested for the two-span RC beams bridging the removed column if the ECA is expected for the collapse resistance. Also, complementary pseudo-static analysis is advised to verify the ECA under realistic dynamic column loss even though the static PAR is recovered in the nonlinear static response. A practical empirical formula is provided to estimate an approximate rotation demand for the ECA.

• 대한토목학회논문집
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• 제31권2A호
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• pp.59-69
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• 2011

성능기반 내진 설계방법의 설계철학을 가지고 있는 비선형 정적 해석법(NSPs)은 최근 구조물의 지진해석방법으로서 그 사용성을 인정받고 있다. 비선형 정적 해석법을 통한 지진해석은 기존의 비선형 시간 이력법에 비해서 방법이 간단하며, 직관적으로 구조물의 지진해석을 수행할 수 있는 등의 장점으로 빌딩구조물의 지진해석법으로 널리 사용되고 있다. 하지만, 기본 진동모드에 의해서 구조물의 거동이 지배되지 않는 구조물의 경우에는 그 사용성에 대한 연구가 매우 제한적이다. 이를 개선하기 위한 고차모드의 기여분을 반영할 수 있는 비선형 정적 해석법으로 모드별 비탄성 정적해석법(Modal Pushover Analysis; MPA)이 제시되었고, 또한 이를 개선한 개선된 모드별 비탄성 정적해석법(Improved Modal Pushover Analysis; IMPA) 역시 소개되었다. 본 논문에서는 기존에 소개된 네가지 비선형 정적 해석법을 이용하여 국내에 설계/시공된 두 사장교의 지진해석 가능성을 알아보며, 각 방법의 장/단점을 분석 하여 비선형 정적 해석법의 응용가능성에 대해서 알아보았다.

• Geomechanics and Engineering
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• 제8권1호
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• pp.97-111
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• 2015

The kinematical approach of limit analysis is used to estimate the three dimensional stability analysis of rock slopes with nonlinear Hoek-Brown criterion under earthquake forces. The generalized tangential technique is introduced, which makes limit analysis apply to rock slope problem possible. This technique formulates the three dimensional stability problem as a classical nonlinear programming problem. A nonlinear programming algorithm is coded to search for the least upper bound solution. To prove the validity of the present approach, static stability factors are compared with the previous solutions, using a linear failure criterion. Three dimensional seismic and static stability factors are calculated for rock slopes. Numerical results of indicate that the factors increase with the ratio of slope width and height, and are presented for practical use in rock engineering.

• Advances in Computational Design
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• 제7권2호
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• pp.99-112
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• 2022

This research has been devoted to examine nonlinear static bending analysis of smart beams with nano dimension exposed to thermal environment. The beam elastic properties are corresponding to piezo-magnetic material of different compositions. The large deflection analysis of the beam has been performed assuming that the beam is exposed to transverse uniform pressure. Based on the rule of Hamilton, the governing equations have been derived for a nonlocal thin beam and solved using differential quadrature method. Temperature variation effect on nonlinear deflection of the smart beams has been studied. Also, the beam deflection is shown to be affected by electric voltage, magnetic intensity and material composition.

• 한국지진공학회논문집
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• 제24권2호
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• pp.77-86
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• 2020

Nonlinear static analysis and preliminary evaluation were performed in this study to evaluate the seismic performance of unreinforced masonry buildings subjected to various soil conditions based on the revised Korean Building Code. Preliminary evaluation scores and nonlinear static analyses indicated that all buildings were susceptible to collapse and did not reach their target performance. Therefore, retrofit of those building models was carried out through a systematic procedure to determine areas to be strengthened. It was possible to make most building models satisfy performance objectives through the reinforcement alone of damaged external shear walls. However, the application of a preliminary evaluation procedure to retrofit design was found to be too conservative because all the retrofitted building models verified with nonlinear static analysis failed to satisfy performance objectives. Therefore, it is possible to economically retrofit unreinforced masonry buildings through the fortification of external walls if a simple evaluation procedure that can efficiently specify vulnerable parts is developed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1960-1965
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• 2005

This paper presents theory for stability analysis and design of a servo system for a MIMO Wiener system with nonlinear uncertainty. The Wiener system consists of a linear time-invariant system(LTI) in cascade with a static nonlinear part ${\psi}$(y) at the output. We assume that the uncertain static nonlinear part is sector bounded and decoupled. In this research, we treat the static nonlinear part as multiplicative uncertainty by dividing the nonlinear part ${\psi}$(y) into ${\phi}$(y) := ${\psi}$(y)-y and y, and then we reduce this stabilizing problem to a Lur'e problem. As a result, we show that the servo system with no steady state error for step references can be constructed for the Wiener system.

• 한국전산구조공학회논문집
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• 제24권5호
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• pp.569-576
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• 2011

본 논문에서는 비선형정적해석 방법을 이용하여 기존의 연쇄붕괴 선형정적해석 절차에 수반되는 반복과정을 자동으로 수행하면서도 선형해석 결과와 동일한 결과를 나타내는 새로운 연쇄붕괴 해석절차를 제안하였다. 제안된 해석절차는 GSA 기준에 규정된 기존 선형정적해석법의 단점인 반복적 해석작업 및 그 과정에서 발생할 수 있는 시간과 오류의 가능성을 최소화하여 해석결과의 신뢰성을 확보가 있는 선형정적해석 절차이다. 제안된 해석절차를 검증하기 위하여 철근콘크리트 모멘트골조 및 철골 가새골조의 최하층 기둥부재를 제거한 후 기존 해석법과 제안 해석법을 적용하고 그 결과를 비교 분석하였다. 해석결과에 따르면 제안된 해석절차는 구조물의 붕괴여부의 판정 및 힌지 분포에 있어서 기존의 선형정적해석과 동일한 결과를 나타내었으며, 반복해석 과정이 불필요하므로 기존 해석법에 비하여 매우 짧은 시간에 해석을 수행할 수 있는 것으로 나타났다.

• Wind and Structures
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• 제13권1호
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• pp.1-20
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• 2010

The recommended factored design wind load effects for overhead lattice transmission line towers by codes and standards are evaluated based on the applicable wind load factor, gust response factor and design wind speed. The current factors and design wind speed were developed considering linear elastic responses and selected notional target safety levels. However, information on the nonlinear inelastic responses of such towers under extreme dynamic wind loading, and on the structural capacity curves of the towers in relation to the design capacities, is lacking. The knowledge and assessment of the capacity curve, and its relation to the design strength, is important to evaluate the integrity and reliability of these towers. Such an assessment was performed in the present study, using a nonlinear static pushover (NSP) analysis and incremental dynamic analysis (IDA), both of which are commonly used in earthquake engineering. For the IDA, temporal and spatially varying wind speeds are simulated based on power spectral density and coherence functions. Numerical results show that the structural capacity curves of the tower determined from the NSP analysis depend on the load pattern, and that the curves determined from the nonlinear static pushover analysis are similar to those obtained from IDA.