• Structural Engineering and Mechanics
• /
• 제58권6호
• /
• pp.1021-1044
• /
• 2016

Different versions of a damage index (DI) along with a formulation to find the number of cycles at failure due to fatigue, applicable to reinforced concrete (RC) structures are presented. These are based on an energetic analysis method and applicable to both global and local levels. The required data can be found either from the numerical simulation of structures or from the experimental tests. A computer program has been developed to simulate numerically the nonlinear behavior of RC columns under cyclic loading. The proposed DI gives a regular distribution of structural damages up to failure and is validated by the results of the tests carried out on RC columns subjected to cyclic loading. In general, the local and global damage indices give approximately similar results, while each of them has its own advantages. The advantage of the implicit version of DI is that, it allows the comparison of the results with those of the monotonic loading case, while the explicit version makes it possible to estimate the number of loading cycles at failure due to fatigue, and the advantage of the simplified version is that; the monotonic loading data is not needed for the cyclic loading case.

• 대한기계학회논문집
• /
• 제12권3호
• /
• pp.528-533
• /
• 1988

본 연구에서는 피스톤의 온도분포 및 열변형을 유한요소법에 의해 분석할 경 우 입력 데이타로 주어질 경계조건은 Li가 사용한 열저항 회로법을 근거로 하여 여기 에 경험치를 부여하는 방법으로 초기 설정치를 구하고, 또 전해질 탱크 상사법에 의한 실험적인 방법으로 결과를 구하여서 두 결과를 비교 검토하고자 한다.

• 대한교통학회지
• /
• 제22권4호
• /
• pp.19-30
• /
• 2004

현재 국내에서는 물류시설의 부족, 물류시설의 비효율적 운영, 복잡한 유통구조, 물류산업의 낙후, 폐쇄적 정보 이용 등으로 인하여 필요 이상의 물류비용이 발생하고 있다. 이런 문제들을 해결하기 위해서는 물류구조의 전반적인 개선 및 물류시설의 확충 등이 필요하다. 하지만, 이러한 노력들이 기존의 원단위식 규모예측으로 이루어진다면 차량의 하역특성을 세밀히 고려하지 못하게 되고, 또한 향후 하역작업의 기계화 및 자동화 등으로 인한 작업능률의 향상을 반영하지 못 할 우려가 있다. 따라서 본 연구는 화물터미널에서의 화물차량의 이용현황을 기초로 대기행렬이론(queueing theory)을 적용함으로써 화물차량의 하역특성이 고려된 화물터미널의 최적규모산정법을 제시하였다. 또한, 현재의 하역시스템에서 이루어지는 작업들이 기계화 및 자동화, 정보화되었을 경우에는 화물터미널의 최적규모에 어떠한 영향을 미치는가에 대해 분석하였다. 분석결과, 하역시간의 규칙성 증가가 화물터미널의 규모변화에 미치는 영향은 크지 않은 것으로 나타났으며, 하역속도 및 서비스율의 향상은 화물터미널의 규모변화에 매우 큰 영향을 미치는 것으로 나타났다.

• 대한치과보철학회지
• /
• 제44권5호
• /
• pp.584-593
• /
• 2006

Statement of problem : Dental implant which has been developed gradually through many experiments and clinical applications is presently used to various dental prosthetic treatments. To conduct a successful function of implant prosthesis in oral cavity for a long time, it is important that not only structure materials must have the biocompatibility, but also the prosthesis must be designed for the stress, which is occurred in occlusion, to scatter adequately of load support. Therefore, it is essential to give the consideration about the stress analysis of supporting tissues for higher successful rates. Purpose : Recently, many implant manufacturing company produce various taper design of root form implant, the fixture is often selected. However, the stress analysis of taper form fixture still requires more studies. Material and method : This study we make the element models that five implant fixture; Branemark system(Nobel Biocare, Gothenberg, Sweden), Camlog system(Altatec, Germany), Astra system(Astra Tech, Sweden), 3i system(Implant Innovations Inc, USA), Avana system(Osstem, Korea) were placed in the area of mandibular first premolar and prosthesis fabricated, which we compared with stress distribution using the three-dimension finite element analysis under two loading condition. Results : This study compares the aspect of stress distribution of each system with the standard of Von mises stress, among many resulted from finite element analysis so that this research gets the following results. 1. In all implant system, oblique loading of maximum Von mises stress of implant, alveolar bone and crown is higher than vertical loading of those. 2. Regardless of loading conditions and type of system, cortical bone which contacts with implant fixture top area has high stress, and cancellous bone has a little stress. under the vertical loading, maximum Von mises stress is more higher in order of Branemark, Camlog, Astra, 3i, Avana. under the horizontal loading, maximum Von mises is more higher in order of Camlog, Branemark, Astra, 3i, Avana.

• Structural Engineering and Mechanics
• /
• 제55권4호
• /
• pp.885-900
• /
• 2015

This paper introduces Romberg-Richardson's method as one of the numerical integration tools for computation of stress intensity factor in a pre-cracked specimen subjected to a complex stress field across the crack faces. Also, the computation of stress intensity factor for various stress fields using existing three methods: average stress over interval method, piecewise linear stress method, piecewise quadratic method are modified by using Richardson extrapolation method. The direct integration method is used as reference for constant and linear stress distribution across the crack faces while Gauss-Chebyshev method is used as reference for nonlinear distribution of stress across the crack faces in order to obtain the stress intensity factor. It is found that modified methods (average stress over intervals-Richardson method, piecewise linear stress-Richardson method, piecewise quadratic-Richardson method) yield more accurate results after a few numbers of iterations than those obtained using these methods in their original form. Romberg-Richardson's method is proven to be more efficient and accurate than Gauss-Chebyshev method for complex stress field.

• Journal of Electrical Engineering and Technology
• /
• 제13권1호
• /
• pp.315-325
• /
• 2018

This paper investigates optimum air-gap flux distribution with third harmonic rotor flux orientation adjustment for five-phase induction motor. The technique of objective is to generate a nearly rectangular air-gap flux, and it improves iron utilization under variation loading conditions. The proportional relations between third harmonic and fundamental plane currents is usually adopted in the conventional method. However, misalignment between fundamental and third harmonic component occurs with variation loading. The iron of stator teeth is saturated due to this misalignment. This problem is solved by third harmonic rotor flux orientation adjustment simultaneously, and direction and amplitude are changed with mechanical load variation. The proposed method ensures that the air-gap flux density is near rectangular for a maximum value from no load to rated load. It is confirmed that the proposed method guarantees complete both planes decoupling with third harmonic flux orientation adjustment. The effectiveness of the proposed technique is validated experimentally.

• Structural Engineering and Mechanics
• /
• 제41권3호
• /
• pp.313-337
• /
• 2012

A three-dimensional formulation is proposed to analyze the lateral loading distribution of external actions in high-rise buildings. The method is extended to encompass any combination of bracings, including bracings with open thin-walled cross-sections, which are analyzed in the framework of Timoshenko-Vlasov's theory of sectorial areas. More in detail, the proposed unified approach is a tool for the preliminary stages of structural design. It considers infinitely rigid floors in their own planes, and allows to better understand stress and strain distributions in the different bearing elements if compared to a finite element analysis. Numerical examples, describing the structural response of tall buildings characterized by bracings with different cross-section and height, show the effectiveness and flexibility of the proposed method. The accuracy of the results is investigated by a comparison with finite element solutions, in which the bracings are modelled as three-dimensional structures by means of shell elements.

• Wind and Structures
• /
• 제1권4호
• /
• pp.317-336
• /
• 1998

In this paper the appraisal of a folding dome structure under the influence of wind loading is discussed. The foldable structure considered is constructed from an assembly of interconnected elements, together with a flexible membrane, all of which are initially store in a compact form and on deployment expand, like an umbrella, into a dome structure. Loading on the dome was obtained from a wind tunnel analysis of the pressure distribution over the roof of a 1:10 scale model of the structure. The critical loading obtained from the wind tunnel investigation was used, together with individual member and material tests, to form a series of numerical non-linear finite element models which were, in turn, used to investigate the forces within the structure. The numerical analysis was used to determine the critical wind loading that the structure can sustain, as well as providing a method by which to investigate the failure modes of the structure. In order to enhance the load carrying capacity of the dome it was found that both the strength and stiffness of the structural nodes needed to be enhanced and in addition, changes were necessary to substantially increase the stiffness of the individual member and caps.

• Structural Engineering and Mechanics
• /
• 제31권6호
• /
• pp.679-696
• /
• 2009

The paper aims at analyzing the stress distribution around an underground opening that is subjected to non-symmetrical surface loading with emphasis on opening shapes with sharp corners and the stress concentrations developed at these locations. The analysis is performed utilizing the BIE method coupled with the Neumann's series. In order to implement this approach, the special recurrent relations for half plane were proven and the modified Shanks transform was incorporated to accelerate the series convergence. To demonstrate the capability of the developed approach, a horseshoe shape opening with sharp corners was investigated and the location and magnitude of the maximum hoop stress was calculated. The dependence of the maximum hoop stress location on the parameters of the surface loading (degree of asymmetry, size of loaded area) and of the opening (the opening height) was studied. It was found that the absolute magnitude of the maximum hoop stress (for all possible surface loading locations) is developed at the roof points when the opening height/width ratio is relatively large or when the pressure loading area is relatively narrow (compared to the roof arch radius), and contrarily, when the opening height/width ratio is relatively small or when the surface pressure is applied to a relatively wide area, the absolute magnitude of the maximum hoop stress is developed at the bottom sharp corner points.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 추계학술대회 논문집
• /
• pp.254-256
• /
• 2009

The performances of proton exchange membrane (PEM) water electrolysis depend on many factors such as materials, geometries, fabrication methods, operating conditions, and so forth. The fabrication method is concerned, membrane electrode assemblies (MEA) are a most important part to show different performances by different fabrication methods. The performance change of PEM water electrolysis was experimentally measured according to the fabrication differences of the anode electrodes. One point of view is the catalyst intrusion rate to the anode gas diffusion layer (GDL), and the other point of view is the catalyst loading distribution in depth of the anode GDL. Results show that the performances of MEA with deep intrusion of the catalysts are better in the range of low current densities but worse at higher current densities. The catalyst loading distribution does not affect significantly to the performance of PEM water electrolyser.