자율비행 개인항공기용 주익 조립체 등가모델 동특성 해석

김현기,김성준 항공우주시스템공학회 2021 항공우주시스템공학회지 Vol.15 No.1

본 연구에서는 신개념 항공교통수단으로 활용될 자율비행 개인항공기 개발의 일환으로 자율비행 개인항공기 주익조립체의 등가모델을 생성한 후 고유모드 해석을 통해 생성된 등가모델의 신뢰성을 검증하였다. 주익조립체는 주익, 안쪽파드, 바깥쪽 파드로 구성되어 있다. 먼저, 각 부품의 등가모델을 생성하기 위해서 해당 부품을 몇 개의 구역으로 분할하고, 각 구역의 양 끝단에 등가모델 축상에 놓이는 절점들을 생성하였다. 그리고, 단위하중과 단위모멘트을 부과한 정적해석을 통해 변형량 또는 회전량을 계산하고, 빔 이론식을 적용하여 각 부품들의 등가 축강성, 굽힘강성, 비틀림강성을 계산하였다. 그리고, 각 구역 중앙에 집중질량을 생성하여 질량과 관성모멘트 정보를 입력하고, 빔 요소를 사용하여 등가모델을 생성하였다. 최종적으로 상세모델의 모드해석 결과와의 비교를 통해 생성된 등가모델의 신뢰성을 확인하였다. In this study, as part of the development of an autonomous flying personal aircraft, an equivalent model of the main wing assembly of an Optionally Piloted Personal Air Vehicle (OPPAV) was developed. Reliability of the developed equivalent model was verified by eigenvalue analysis. The main wing assembly consisted of a main wing, an inboard pod, and an outboard pod. First, for developing an equivalent model of each component, components to produce the equivalent model were divided into several sections. Nodes were then created on the axis of the equivalent model at both ends of each section. In addition, static analysis with unit force and unit moment was performed to calculate the deformation or the amount of rotation at the node to be used in the equivalent model. Equivalent axial, bending, and torsional stiffness of each section were calculated by applying the beam theory. Once the equivalent stiffness of each section was calculated, information of a mass and moment of inertia for each section was entered by creating a lumped mass in the center of each section. An equivalent model was developed using beam element. Finally, the reliability of the developed equivalent model was verified by comparison with results of mode analysis of the fine model.

철골 모멘트 골조의 지진해석을 위한 등가 단자유도시스템

한상환,문기훈,김진선 한국지진공학회 2008 한국지진공학회논문집 Vol.12 No.3

다자유도 시스템의 내진 성능을 평가하기 위해서는 반복적인 비선형 시간 이력 해석이 필요하며 이를 위해 많은 계산과정과 노력이 필요하다. 이와 같이 해석에 따르는 어려움을 보완하기 위해 복잡한 다자유도 시스템을 반영할 수 있는 등가 단자유도 시스템을 개발하였다. 등가 단자유도의 이력 모델로는 일반적으로 이선형 모델과 삼선형 모델이 사용된다. 이러한 모델은 탄성 거동 이후 음강성을 가질 수 있도록 하여 지진 발생 시 중력하중에 의한 발생되는 효과를 반영하기 위해서이다. 본 연구에서는 철골모멘트 골조의 실제 응답을 예측하기 위하여 이러한 이력 모델들로 거동하는 등가단자유도 시스템의 필요조건에 대하여 평가하였다. 이를 위해 본 연구에서는 로스엔젤레스 지역의 SAC 9층 모멘트 저항 골조를 비선형 다자유도 시스템과 등가단자유도 시스템으로 모델링하여 반복하중 푸쉬오버 해석, 비선형 시간 이력해석 및 IDA(Incremental Dynamic Analysis)를 수행하여 비교 검토하였다. 또한 본 연구에서는 강도저감 모델에 대해서도 평가를 수행하였다. 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.

등가선형 및 이선형 납-고무받침 모델을 적용한 면진된 원전구조물의 지진 취약도 해석

이진희,송종걸 한국지진공학회 2015 한국지진공학회논문집 Vol.19 No.5

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.

등가 모델을 이용한 불국사 극락전의 구조해석

박경훈(Park Kyoung-Hoon),최현훈(Choi Hyun-Hoon),김진구(Kim Jin-Koo),윤재신(Yoon Chae-Sin) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.1

The purpose of this study is to develop an simplified equivalent model to investigate the structural behavior of the Gukrak-Paviliion of Bulkuk-Temple subjected to gravity load using a three-dimensional structural analysis. The structural analysis of the traditional wooden structure is difficult because they are connected by mortise locks, dovetails and so on which are difficult to model. Especially bracket sets are congested with many members such as Salmi and Chumcha and may be analyzed correctly only by three-dimensional finite element model. In this study the bracket sets are modeled by equivalent linear members in such a way that the energy of the bracket sets is equal to that of the equivalent model. According to the analysis results the vertical deflection of the bracket sets obtained using the equivalent model is in good agreement with the displacement obtained by finite element model. The analysis results using the equivalent linear model showed that some members such as the connecting beams, architraves, and roof purlines located across the wide span are under stress close to or even larger than the allowable stress.

광대역유도분극 이상 자료의 해석을 위한 새로운 등가회로 모델

신승욱 ( Seung Wook Shin ),박삼규 ( Samg Yu Park ),신동복 ( Dong Bok Shin ) 한국지구물리·물리탐사학회 2014 지구물리와 물리탐사 Vol.17 No.4

지층의 전기화학적인 물성을 이용한 광대역유도분극(SIP) 탐사는 황화광물을 포함한 금속광물탐사에 유용한 기술이다. 탐사자료로부터 IP 물성을 계산하기 위해서는 등가회로 분석을 수행한다. 분석에 사용되는 암석의 SIP 반응을 고려한 등가회로 모델은 해의 비유일성이라는 문제를 가지기 때문에 정확한 분석을 위해 적절한 모델을 설정하는 것이 매우 중요하다. 따라서 이 연구는 SIP 이상반응을 나타내는 광석의 분석에 적합한 새로운 모델을 제안하고자 하였다. 이 모델은 기존의 Dias model과 Cole-Cole model의 비교를 통하여 적합성을 검증하였다. 그 결과, Dias model과 Cole-Colemodel을 이용한 분석 결과의 NRMSE 오차는 각각 10.05%와 17.03%를 보였다. 하지만 제안한 새로운 모델의 NRMSE오차는 0.87%로 상당히 낮았기 때문에 다른 모델보다 SIP 이상 자료의 등가회로 분석에 유용하고 판단하였다. Spectral induced polarization (SIP) is a useful technique, which uses electrochemical properties, for explorationof metallic sulfide minerals. Equivalent circuit analysis is commonly conducted to calculate IP parameters from SIP data. An equivalent circuit model, which indicates the SIP response of rock, has a non-uniqueness problem. For this reason,it is very important to select the proper model for accurate analysis. Thus, this study focused on suggesting a new model,which suitable for the analysis of an anomalous SIP response, such as ore. A suitability of the new model was verifiedby comparing it with the existing Dias model and Cole-Cole models. Analysis errors were represented as a normalizedroot mean square error (NRMSE). The analysis result using the Dias model was the NRMSE of 10.50% and was theNRMSE using the Cole-Cole model of 17.03%. Howerver, because the NRMSE of the new model is 0.87%, it isconsidered that the new model is more useful for analyzing the anomalous SIP data than other models.

등가 1자유도계에 의한 철근콘크리트 건물의 층 변위응답 산정

전대한 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1(구조계)

To evaluate the seismic capacity of a multi story building structures in performance based seismic design, it is need to convert MDOF model into equivalent SDOF model. This paper presents predictions for story displacements of multistorey structures using method of converting a MDOF system into an equivalent SDOF model. The principal objective of this investigation is to evaluate appropriateness of converting method through perform nonlinear time history analysis of a multistory building structures and an equivalent SDOF model. Comparing the story displacements of multistorey structures calculated by time history response analysis and those evaluated by an equivalent SDOF model, the adequacy and the validity of converting method is verified. The conclusion of this study is following; A method of converting a MDOF system into an equivalent SDOF model through the nonlinear time history response analysis is valid. Inelastic first mode shapes are expected to be more accurate than elastic first mode shapes in obtaining story displacement of multistorey structures from equivalent SDOF model.

Updating Effects on Equivalent Shear Beam Structure Models for Lower-Order Modes Based on Sensitivity-Based Methods and Artificial Neural Networks

Nien-Lung Lee 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.5

In this study, a building steel structure that adopted an equivalent shear beam structure model is analyzed, with the updating effects on this simplified analysis model discussed using sensitivity-based and artificial neural network (ANN) methods. Due to the limitations of the sensitivity-based structural model updating method, mean absolute relative error was used to evaluate the reasonable number of hidden layer nodes of the ANN multi-layer perceptron architecture to be applied to the updating equivalent shear beam structural model. A National Earthquake Engineering Research Center (Taipei) steel test structure was selected as the case study. The results reveal that the equivalent shear beam structural model updated modal parameter analysis of lower-order modes is more consistent with the modal test than the 3D finite element analysis. A comparison between the discrepancies between the sensitivity-based and ANN methods suggests that the latter outperforms the former, as indicated by its better performance in terms of predicting the first two modal natural frequencies. This finding demonstrates the applicability of the updated equivalent shear beam model and indicates that structural dynamic response analysis can be conducted using the updated stiffness values of each floor. Therefore, this simplified analysis model could be applied to the vibration analysis and design of multi-story structures (e.g., high-rise steel structures, scaffoldings, and vibrating shaking tables). Furthermore, these findings indicate that this simplified analysis model for multi-story structures could also be applied to the evaluation of old structures.

A study on an equivalent model of the threaded fasteners in complex structures through tightening and loosening analysis

Heerok Hong,Ho-Yong Lee,Nak-Tak Jeong,Keon-Hee Baek,Myung-Won Suh 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.3

The threaded fasteners are typical machine components in tightening of the machine parts and structures. In addition, as threaded fasteners are easy to maintenance, these are used extensively from large structures to small electronic devices. However, after the clamping, if repetitive load is applied to the bolt/screw, loosening of the screw occurs. In this study, clamping analysis and loosening analysis are carried out for the M12 bolts which are used for the wheels of commercial vehicles. Since it is difficult to carry out test and finite element analysis (FEA) for the wheels of commercial vehicles, we propose a complex structure to deal with these problems. Through the test and FEA, the clamping force and the loosening load of bolt are derived. Not only the reduction of clamping force but also displacement of the complex structure subjected to load can indicate the loosening of the bolt. Three equivalent models are proposed to replace a detailed model for reduction of the analysis time and cost. Then, the three equivalent models are forms of rigid beam – beam – pretension (RBP), shell – beam – pretension (SBP) and shell – beam – temperature (SBT), respectively. Among these forms, the SBT model is most similar with analysis results of the detailed model. The difference between the analysis results of the detailed model and the SBT model was only 5 %. Based on the SBT model and the detailed model, it is applied to the wheel of the commercial vehicles to be verified. Then, the changes in the clamping force of the detailed model and the SBT model are identified as similar, proving the validity of the equivalent.

등가 1자유도계를 이용한 철근콘크리트 골조건물의 층간변위 응답 산정

강호근,전대한 한국지진공학회 2004 한국지진공학회논문집 Vol.8 No.5

성능설계법에서 다층 건축물의 내진성능을 평가하기 위해서는 다자유도계를 등가 1자유도계로 변환할 필요가 있다. 본 논문은 다자유도계를 등가 1자유도계로 변환하여 다층 골조구조물의 층간변위 응답을 추정하는 방법을 제안한다. 본 연구의 목적은 다층 골조구조물과 등가 1자유도계의 시간이력해석을 수행하여 등가 1자유도계 변환 방법의 타당성을 확인하는 것이다. 다층 골조구조물의 시간이력해석에 의한 층간변위 응답과 등가 1자유도계에 의해 추정된 층간변위 응답을 비교하여, 등가 1자유도계에 의한 층간변위 응답에 대한 추정 방법의 타당성을 확인한다. 본 연구에서 얻어진 결과는 다음과 같다. 시간이력해석을 통하여 다자유도계를 등가 1자유도계로 변환하는 방법의 타당성을 확인할 수 있었다. 다층 골조구조물의 층간변위 응답은 비탄성 1차 모드를 이용한 등가 1자유도계의 변위응답으로부터 보다 정확히 추정할 수 있었다. To evaluate the seismic capacity of a multistorey building structures in performance based seismic design, it is needed to convert MDOF model into equivalent SDOF model. This paper presents predictions for interstory drift of multistorey structures using method of converting a MDOF system into an equivalent SDOF model. The principal objective of this investigation is to evaluate appropriateness of converting method through performing nonlinear time history analysis of a multistory building structures and an equivalent SDOF model. Comparing the interstory drift of multistorey structures calculated by time history analysis and those evaluated by an equivalent SDOF model, the adequacy and the validity of converting method is verified. The conclusion of this study is following; A method of converting a MDOF system into an equivalent SDOF model through the nonlinear time history response analysis is valid. Inelastic first mode shapes are expected to be more accurate than elastic first mode shapes in obtaining interstory drift of multistorey structures from equivalent SDOF model.

모형개발 및 검증과정에서 모형의 동치성이 가져오는 문제

이순묵(Soonmook Lee) 한국교육평가학회 2007 교육평가연구 Vol.20 No.3

  동치모형은 수학적으로는 동일한 의미를 가지므로 자료분석으로는 구분이 되지 않고 내용적으로만 구분이 되는 모형이다. 주어진 경험 자료에 동치모형들을 합치시킬 때 합치도가 동일하기 때문이다. 연구자는 주어진 모형에 대하여, 자료수집 이전에 동치 (equivalent)모형을 파악하므로써 자료에 의한 검토의 대상을 좁힐 수가 있다. 또한 자료에 비추어 합치도가 높고 내용상 적절하여 선택되는 모형 역시 이론적으로 상이한, 그러나 수학적으로는 구분이 안되는 다수의 적절한 모형에 비추어 방어될 수 있어야 할 것이다. 그러한 목적으로 주어진 모형에 대해서 경험 자료의 도움이 없이 동치모형을 유도해 낼 수 있는 사전적 규칙이 필요하다. 이 글에서는 그러한 규칙들을 소개하고 현재의 구조방정식 모형에 어떻게 활용될 수 있으며 어떤 의미를 가지는지를 논의한다.   It has been widely known that there may be models that are equivalent to a given model in applications of structural equation modeling. Equivalent models show identical values on any fit measure so that they are distinguished not by mathematics of fit measures, but by substantive interpretations. However, the issue has not been well taken in applied research. It is the purpose of the present study to introduce two rules for deriving equivalent models and demonstrate existence of meaningful equivalent models to models in the published articles. The demonstrations will emphasize that authors of research are required to defend his/her models against equivalent models that have potentiality of substantive meaning. That kind of practice would be needed at three time points in the process of research: hypothesis generation stage, during specification search, and after arriving at a final model. At any of these three situations, there is a strong need to know about and apply rules for deriving equivalent models in applications of structural equation modeling.