• Journal of Electrical Engineering and Technology
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• 제7권4호
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• pp.564-569
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• 2012

This paper proposes a hybrid-excited linear synchronous motor (LSM) that has potential applications in a magnetically levitated vehicle. The levitation and thrust force characteristics of the LSM are investigated by means of three-dimensional (3-D) numerical electromagnetic FEM calculations and experimental verification. Compared to a conventional LSM with electromagnets, a hybrid-excited LSM can improve levitation force/weight ratios, and reduce the power consumption of the vehicle. Because the two-dimensional (2-D) FE analysis model describes only the center section of the physical device, it cannot express the complex behavior of leakage flux, which this study is able to predicts along with levitation and thrust force characteristics by 3-D FEM calculations. A static force tester for a hybrid-excited LSM has been manufactured and tested in order to verify these predictions. The experimental results confirm the validity of the 3-D FEM calculation scheme for the description of a hybrid-excited LSM.

• Steel and Composite Structures
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• 제19권1호
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• pp.59-74
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• 2015

Since there are several places located in active seismic zones in the world, serious damages and losses have happened due to major scaled earthquakes. Especially, structures having different irregularities have been severely damaged or collapsed during these seismic events. Behavior of existing structures under several loading conditions is not completely determined due to some uncertainties. This situation reveals the importance of design and analysis of structures under seismic effects. Several non-linear static procedures have been developed in recent years. Determination of the seismic safety of the existing structures and strengthening techniques are significant civil engineering problems Non-linear methods are defined in codes to determine the performance levels of structures more accurately. However, displacement based ones give more realistic results. These methods provide more reliable evaluation possibilities for existing structures with developing computer technology. In this study, non-linear performance analysis of existing and strengthened steel structures by X shaped bracing members with 3, 5 and 7 stories which have soft story irregularity is performed according to FEMA-356 and Turkish Earthquake Code-2007. Damage ratios of the structural members and global performance levels are determined as well as modal properties and story drift ratios after non-linear finite elements analysis for each structure.

• 한국수소및신에너지학회논문집
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• 제26권3호
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• pp.294-299
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• 2015

Free piston linear engine (FPLE) is a promising concept being explored in the mid-20th century. On the other hand, Arficial neural networks (ANNs) are non-linear computer algorithms and can model the behavior of complicated non-linear processes. Some researchers already studied this method to predict internal combustion engine characteristics. However, no investigation to predict the performance of a FPLE using ANN approach appears to have been published in the literature to date. In this study, the ability of an artificial neural network model, using a back propagation learning algorithm has been used to predict the in-cylinder pressure, frequency, maximum stroke length of a free piston linear engine. It is advised that, well-trained neural network models can provide fast and consistent results, making it an easy-to-use tool in preliminary studies for such thermal engineering problems.

• 대한기계학회논문집A
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• 제20권1호
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• pp.127-134
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• 1996

In general, seismic isolators which are made of laminated rubber and shim plate have characteristics of complex hysteretic behavior. When shear deformation of the seismic isolator is small, the isolator hassimple hysteretic almost bi-linear behabior. But on large shear deformation hardening effects may occur. This paper proposes a moldeling method of the seimic isolator with modified hysteretic bi-linear model which can consider the hardening effects. From the results of the seismic analyses of the isolated system it is shown that the responses are singificantly reduced compared with those of the non-isolated system. The modified hysteretic bi-linear model of the isolator gives larger ZPA(zero period acceleration) than those of the simple hysteretic bi-linear model and the equivalunt spring-damper model.

• 한국지진공학회논문집
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• 제19권1호
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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.

• Structural Engineering and Mechanics
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• 제14권3호
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• pp.331-343
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• 2002

Because of the increasing span of arch bridges, ultimate capacity analysis recently becomes more focused both on design and construction. This paper investigates the static and ultimate behavior of a long-span steel arch bridge up to failure and evaluates the overall safety of the bridge. The example bridge is a long-span steel arch bridge with a 550 m-long central span under construction in Shanghai, China. This will be the longest central span of any arch bridge in the world. Ultimate behavior of the example bridge is investigated using three methods. Comparisons of the accuracy and reliability of the three methods are given. The effects of material nonlinearity of individual bridge element and distribution pattern of live load and initial lateral deflection of main arch ribs as well as yield stresses of material and changes of temperature on the ultimate load-carrying capacity of the bridge have been studied. The results show that the distribution pattern of live load and yield stresses of material have important effects on bridge behavior. The critical load analyses based on the linear buckling method and geometrically nonlinear buckling method considerably overestimate the load-carrying capacity of the bridge. The ultimate load-carrying capacity analysis and overall safety evaluation of a long-span steel arch bridge should be based on the geometrically and materially nonlinear buckling method. Finally, the in-plane failure mechanism of long-span steel arch bridges is explained by tracing the spread of plastic zones.

• 한국지진공학회논문집
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• 제14권4호
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• pp.49-60
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• 2010

구조부재와 구조시스템의 실제 비탄성 이력거동은 완만한 형태를 나타낸다. 완만한 곡선형 이력거동이 이선형 또는 분할선형 강성저하모델등에 비하여 실제 거동을 정확하게 나타낸다. 내진설계에서 강도감소계수는 탄성 거동만 허용한 경우에 요구되는 강도를 설계수준의 강도로 감소시키는데 사용된다. 강도감소계수에 대한 완만한 곡선이력거동의 영향을 근거리 지진과 원거리 지진을 받는 몇 가지 완만한 곡선이력 시스템에 대하여 평가하였다. 설계 목적을 위하여 이력거동의 완만정도와 근거리와 원거리 지진으로 대변될 수 있는 지진특성을 고려하는 간단한 강도감소계수 식을 제안하였다. 본 연구의 제안식에 의한 강도감소계수가 기존의 제안식에 의해 평가된 강도감소계수보다 비탄성 응답스펙트럼 해석으로부터 직접적으로 구한 강도감소계수에 근접한 결과를 나타낸다.

• 한국강구조학회 논문집
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• 제14권4호
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• pp.489-497
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• 2002

구조물이 거대해지고 복잡해지면서 미소변현을 전제로 한 선형이론으로는 해석이 불가능한 대변형 및 비선형 거동이 발생하는 경우가 많아지고 있다. 또한 고성능 컴퓨터의 등장과 다양한 수치해석 기법의 개발 등으로 보다 엄격한 설계기준에 따른 구조의 최적화 설계가 절실히 요구되고 있다. 그로 인해 선형 영역내에서 한정되었던 구조공학적인 문제를 비선형 영역까지 확대시켜 구조물의 거동을 보다 정확히 분석하고, 예상 가능한 문제점을 사전에 파악하여 효율적이고 경제적인 최적의 구조물을 설계해야 한다. 본 연구에서는 비등방성 원통형 쉘 구조물의 기하학적 비선형 문제를 해결하였다. 원통형 쉘의 반경방향 길이와 원통방향의 길이비인 형상비 변화, 부분 원통형 쉘의 중심각 변화, 화이버 각도 변화, 적층수와 배열조건 변화 등의 다양한 조건에 따라 비등방성 원통형 쉘 구조의 기하학적 비선형 거동특성을 분석하였다.

• Journal of the Korean Wood Science and Technology
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• 제27권3호
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• pp.23-30
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• 1999

경골 목조 트러스를 접합하는데 가장 널리 사용되는 메탈 플레이트 접합부의 거동을 해석하기 위한 연구가 많이 수행되어왔다. 유한요소법을 사용한 해석은 그 연구들중의 하나이다. 선형 모델을 사용한 유한요소법은 하중-변위 곡선의 초기 경사를 예측하는데는 유효하게 사용될 수 있다. 하지만, 하중이 증가할수록 예측된 변위는 실험치에 비해 과예측이 된다. 따라서 선형 모델을 비선형부분을 예측하는데는 사용할 수 없다. 실제 거동을 더욱 정확하게 예측하기 위해, 본 연구에서는 비선형 항을 유한요소 모델에 첨가시켰다. EA와 AA 형태에서는 예측치와 실험치간에 고도의 유사성을 보여주었다. 하지만, EE와 AE 형태에서는 곡선의 비선형 부분에서 실험치와 예측치가 약간의 차이를 보여주었다. 이러한 결과는 슬립의 효과를 충분히 반영하지 못한 것에 기인한 것으로 추측된다. 결과적으로 메틸플레이트 접합부의 거동에 있어서 비선형 해석의 정확도를 증진시키기 위해서는 반드시 슬립의 효과가 고려되어야 할 것이다.

• Computers and Concrete
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• 제31권6호
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• pp.537-543
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• 2023

To study the seismic behavior of recycled aggregate concrete filled circular steel tube (RACFCST) frames, the seismic behavior experiment of RACFCST frame was carried out to measure the hysteresis curve, skeleton curve and other seismic behavior indexes. Moreover, based on the experimental study, a feasible numerical analysis model was established to analyze the finite element parameters of 8 RACFCST frame specimens, and the influence of different variation parameters on the seismic behavior index for RACFCST frame was revealed. The results showed that the skeleton curve of specimens under different axial compression ratios were divided into three stages: elastic stage, elastic-plastic stage and descending stage, and the descending stage was relatively stable, indicating that the specimen had stronger deformation capacity in the descending stage. With the increase of axial compression ratio, the peak bearing capacity of all specimens reduced gradually, and the reduction was less than 5%. With the decrease of beam-column linear stiffness ratio, the peak bearing capacity decreased gradually. With the decrease of yield bending moment ratio of beam-column, the peak bearing capacity decreased gradually, and the decreasing rate of peak bearing capacity gradually accelerated. In addition, compared with the axial compression ratio, the beam-column linear stiffness ratio and the yield bending moment ratio of beam-column had a more significant influence on the peak bearing capacity of RACFCST frame.