• 한국강구조학회 논문집
• /
• 제13권5호
• /
• pp.535-545
• /
• 2001

철골조의 비탄성 거동을 해석하는데 있어 많은 고차해석법이 소개되고 있다. 이 해석법들은 부재의 불완전성과 잔류응력과 같은 재료적인 비선형성 그리고 기하학적 비선형성에 의한 2차 효과를 직접 해석과정에 반영하여 골조의 거동을 좀더 정확히 예측할 수 있다. 이 가운데 비교적 간편하면서도 정확성이 높은 수정소성힌지 해석법을 도입하고 반강접합부의 모델링을 위해 이미 개발하여 제안한 로그 모델을 적용 해석프로그램(RPH-2DF)을 작성하였다. 이 프로그램의 검증을 위해 두께 중복형 접합부를 갖는 골조실험 결과와 해석 결과를 비교하였다. 또한 강접 골조의 거동과 반강 접합부를 갖는 골조의 거동 차이를 규명하기 위해 MIDAS-GEN v4.2.2로 설계된 10층 가새 골조를 대상으로 RPH-2DF를 이용한 해석결과와 비교하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 제40회 하계학술대회
• /
• pp.851_852
• /
• 2009

Shrink fitting which is assembling process to fix stator core on the motor frame is widely used at the mass production line of motors because of cost and productivity. This process produces compressive stress on a stator core, which causes negative effect for example, core and copper losses on motor performance. Magnetic properties of electrical steel are effected by both compressive and tensile and thermal stresses. Electromagnetic field analysis is considered one of the effective process since one can predict motor performance including core loss precisely. This method can consider non linear magnetic property with magnetic saturation which is typical electrical steel behavior. However this method is strongly depended on non linear magnetic data, one may have different calculation result whether considering mechanical stress or not. This study describes magnetic field analysis of a motor considering mechanical stress from shrink fitting. Analysis results are compared with each stress-free and stressed condition.

• Structural Engineering and Mechanics
• /
• 제56권4호
• /
• pp.589-603
• /
• 2015

The mixed-mode stress intensity factors of 2-D angled cracks are evaluated by Petrov-Galerkin natural element (PG-NE) method in which Voronoi polygon-based Laplace interpolation functions and CS-FE basis functions are used for the trial and test functions respectively. The interaction integral is implemented in a frame of PG-NE method in which the weighting function defined over a crack-tip integral domain is interpolated by Laplace interpolation functions. Two Cartesian coordinate systems are employed and the displacement, strains and stresses which are solved in the grid-oriented coordinate system are transformed to the other coordinate system aligned to the angled crack. The present method is validated through the numerical experiments with the angled edge and center cracks, and the numerical accuracy is examined with respect to the grid density, crack length and angle. Also, the stress intensity factors obtained by the present method are compared with other numerical methods and the exact solution. It is observed from the numerical results that the present method successfully and accurately evaluates the mixed-mode stress intensity factors of 2-D angled cracks for various crack lengths and crack angles.

• Structural Engineering and Mechanics
• /
• 제62권3호
• /
• pp.281-289
• /
• 2017

Damping value has considerable influence on the dynamic and seismic behaviors of bridges. However, currently the constant damping ratios that are prescribed by most bridge seismic design codes can't truly represent the complicated damping character of actual structures. In this paper, a cyclic loading experiment was conducted to study the effect of stress amplitude on material damping of concrete to present an analyzing model of the material damping of concrete. Furthermore, based on the fundamental damping of structure measured under ambient vibration, combined with the presented stress-dependent material damping concrete, the seismic response of a bridge pier was calculated. Comparison between the calculated and experiment results verified the validity of the presented damping model. Finally, a modified design and analysis method for bridge was proposed based on stress-dependent damping theory, and a continuous rigid frame bridge was selected as the example to calculate the actual damping values and the dynamic response of the bridge under different earthquake intensities. The calculation results indicated that using the constant damping given by the Chinese seismic design code of bridges would overestimate the energy dissipation capacity of the bridge.

• 한국정밀공학회지
• /
• 제33권9호
• /
• pp.739-744
• /
• 2016

The truck that is used as running equipment for tank freight car support is a core structural part that supports the load of the car body and significantly influences the safety of freights and vehicles, as well as their running performance. Running equipment is composed of truck frames, wheels and wheel axles, independent suspensions, and brakes. Among these components, the truck frame supporting the load of the vehicles and freights may be the most important component. This study was carried out to analyze the structure of truck frames and to determine whether they are safe when the maximum vertical load, braking part load, and the front and rear load are applied to truck frames. This was achieved by subjecting the truck frames to stress tests and then measuring the stress on each part. The results of the stress tests showed that truck frames have a safe vehicle load design.

• Molecules and Cells
• /
• 제27권1호
• /
• pp.47-54
• /
• 2009

A cDNA clone for a transcript preferentially expressed during an early phase of flooding was isolated from Nicotiana tabacum. Nucleotide sequencing of the cDNA clone identified an open reading frame that has high homology to the previously reported glycine-rich RNA-binding proteins. The open reading frame consists of 157 amino acids with an N-terminal RNA-recognition motif and a C-terminal glycine-rich domain, and thus the cDNA clone was designated as Nicotiana tabaccum glycine-rich RNA-binding protein-1 (NtGRP1). Expression of NtGRP1 was upregulated under flooding stress and also increased, but at much lower levels, under conditions of cold, drought, heat, high salt content, and abscisic acid treatment. RNA homopolymer-binding assay showed that NtGRP1 binds to all the RNA homopolymers tested with a higher affinity to poly r(G) and poly r(A) than to poly r(U) and poly r(C). Nucleic acid-binding assays showed that NtGRP1 binds to ssDNA, dsDNA, and mRNA. NtGRP1 suppressed expression of the fire luciferase gene in vitro, and the suppression of luciferase gene expression could be rescued by addition of oligonucleotides. Collectively, the data suggest NtGRP1 as a negative modulator of gene expression by binding to DNA or RNA in bulk that could be advantageous for plants in a stress condition like flooding.

• Earthquakes and Structures
• /
• 제18권2호
• /
• pp.215-222
• /
• 2020

In this paper, slit steel rubber bearing is presented as an innovative seismic isolator device. In this type of isolator, slit steel damper is an energy dissipation device. Its advantages in comparison with that of the lead rubber bearing are its simplicity in manufacturing process and replacement of its yielding parts. Also, slit steel rubber bearing has the same ability to dissipate energy with smaller value of displacement. Using finite element method in ABAQUS software, a parametric study is done on the performance of this bearing. Three different kinds of isolator with three different values of strut width, 9, 12 and 15 mm, three values of thickness, 4, 6 and 8 mm and two steel types with different yield stress are assessed. Effects of these parameters on the performance characteristics of slit steel rubber bearing are studied. It is shown that by decreasing the thickness and strut width and by selecting the material with lower yield stress, values of effective stiffness, energy dissipation capacity and lateral force in the isolator reduce but equivalent viscous damping is not affected significantly. Thus, by choosing appropriate values for thickness, strut width and slit steel damper yield stress, an isolator with the desired behavior can be achieved. Finally, the performance of an 8-storey frame with the proposed isolator is compared with the same frame equipped with LRB. Results show that SSRB is successful in base shear reduction of structure in a different way from LRB.

• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2002년도 추계공동학술대회논문집
• /
• pp.95-100
• /
• 2002

표면효과익선이란 동체의 날개가 해수면 가까이 비행할 때 수면과 날개 사이에서 양력이 증가되는 표면효과를 이용하는 에너지 절약형 선박이다. 표면효과익선은 낮은 고도로 공기 중에서 비행하여야 되므로 박판으로 이루어져야 한다. 그러므로, 표면효과익선 구조에서 외판의 두께는 얇고 가벼우며 Stringer와 Frame등의 보강재는 외판에 비하여 단면적이 훨씬 크다. 이와 같은 구조에 있어서는 외판이 면내방향의 하중을 받으면 박판인 외판은 순전단장에 가깝게 된다. 이와같이 외판과 큰 단면적을 갖는 String를 서로 조합하여 이루어진 구조는 표면효과익선 구조물의 구조응답해석이 가능하다. 본 연구에서는 기본설계 단계에서 간단하게 기체 구조강도해석을 할 수 있는 기존의 해석적인 방법으로 동체와 표면익의 구조강도를 계산할 수 있는 해석적인 방법을 제시하였다.

• 한국가스학회지
• /
• 제12권3호
• /
• pp.31-37
• /
• 2008

본 본문에서는 유한요소법을 사용하여 여러 가지 헬멧 모델의 강도안전에 관한 응력과 변형률을 해석하였다. 차세대 헬멧은 작업자의 안전성과 작업성을 높일 수 있도록 제작되어야 하고, 오랫동안 착용해도 불편함이 없으면서 머리를 보호할 수 있어야 한다. 결국 헬멧은 안전하고, 착용성이 좋아야 하며, 헬멧의 모체 구조물을 가볍게 제작해야 한다. 따라서 헬멧은 화재나 가스폭발과 같은 가혹한 작업조건에 잘 견딜 수 있어야 한다. FEM 해석결과에 의하면, 외부의 충격력이 헬멧모체 구조물의 정상부 지역에 가해졌을 경우 최대응력과 변형률은 하중이 작용되는 지점부위에서 발생하였다. 따라서 헬멧의 모체 구조물에는 보강뼈대를 설치하고 두께를 늘려서 강도안전성을 확보하는 것이 중요하다. 반면에 헬멧의 일반적인 균일한 두게는 줄여서 헬멧의 경량화를 추구하는 것도 중요하다.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2005년도 춘계학술대회 논문집
• /
• pp.361-364
• /
• 2005

Some bogie frames manufactured in 1999, 2000 year have the fatal problem. Three or four years later, the cracked end beam among them have discovered in 2002, 2003 year. The crack situation of the end beam have a bad effect on brake system. In that case, the cars would be in danger of derailment. To improve the end beam, a research of covering the whole field of welded type bogie frame was started. Main line real tests were performed at Young-Dong line. The stress of main positions for bogie frame was measured. Also up-down direction and left-right direction vibration acceleration of the bogie frame were measured. At this time the tests were performed for the three types bogie. The test result concludes that the crack cause of the end beam is not brake load but vibration at running mainly. It is estimated that the life of the improved car which end beam reinforced is safe within the car permitted life(25 years). The improvement methods of the end beam are presented by construction modification, parts modification. The integrity evaluation is inspected by analysis the real line test results, the improvement methods of the end beam.